Application of Underfloor Air Distribution in Hospital Building

APPLICATION OF UNDERFLOOR AIR DISTRIBUTION IN HOSPITAL BUILDING PROJECT SUBMITTED IN PARTIAL FULFILLMENT OF REQUIREMENTS FOR THE AWARD OF THE DEGREE OF BACHELOR OF TECHNOLOGY (FACILITIES AND SERVICES PLANNING)

By

P. Praveen 18011BB038 Under the supervision of

S.K. Naimuddin Asst. Professor, SPA, JNAFAU, Hyderabad.

Department of Building Technology & Services SCHOOL OF PLANNING AND ARCHITECTURE JAWAHARLAL NEHRU ARCHITECTURE & FINE ARTS UNIVERSITY Mahaveer Marg, Hyderabad - 500028

2022

JNAFAU SCHOOL OF PLANNING AND ARCHITECTURE Mahavir Marg, Hyderabad – 500028 DEPARTMENT OF BUILDING TECHNOLOGIES AND SERVICES CERTIFICATE OF APPROVAL I/We certify that the Facilities & Services Planning thesis entitled Application of Underfloor Air Distribution in Hospital Building submitted by P. Praveen bearing Roll No. 18011BB038 on this day of __________ 2022 in partial fulfillment of the requirements for the award of Degree of BACHELOR OF TECHNOLOGY (FACILITIES & SERVICES PLANNING) of this University, is a bonafide work to the best of my/our knowledge and is placed before the Examination Board for consideration.

Mr S.K. Naimuddin

Dr S. Santosh Kumar

Thesis Supervisor

Thesis Coordinator

Ar. Divya Vora

External Examiner

Head of the Department

Dr S. Kumar Principal

Acknowledgement I would like to express my sincere thanks to my guide Mr S.K. Naimuddin, Asst. Professor, SPA, JNAFAU for his constant guidance and blessings throughout the project.

I extend my thanks to all the faculty panel members - Mr B. Ramakrishnaiah, Mr K. Chandrakanth, Mr M. Vinay Kumar, Ms J. Chaitanya, Dr S. Santosh Kumar, Dr K. Srinivas, and Mr Mukheem Basha for the constant encouragement and for their insightful inputs and suggestions.

I am also inspired by the efforts of Dr S.Kumar, Principal, JNAFAU SPA; Dr V. Phanisree, Vice-Chancellor, JNAFAU SPA; and Ar. Divya Vora, Head of the Department, FSP, for introducing us to various opportunities.

My sincere gratitude to Mr Md. Khaleed, Sr. MEP Engineer, V.K Building Services Pvt Ltd and Mr T. Venkata Nagendra, MEP Manager, My Home Constructions Pvt Ltd for their constant support and guidance throughout the thesis work and for imparting their knowledge to me.

I am grateful to Mr Mustufa Rasiwala, Managing Director, AET Flexiblespace Pvt Ltd and his team - Mr Muralidharan Moorthy, Mr Arul Prasanth, and Mr Chandra Pratap for their assistance while doing the case study.

P. Praveen

Abstract As concern for the environment has been dramatically raised over the recent decades, all fields have increased their efforts to reduce the impact on the environment. The field of construction has responded and started developing building performance strategies and regulations to reduce the impact on the environment. HVAC systems are obviously one of the critical factors in building energy consumption.

Underfloor air distribution (UFAD) systems are innovative methods for delivering space conditioning in buildings while reducing life cycle costs and reducing environmental impact.

The purpose of this paper is to propose a UFAD system for a hospital building and to create an efficient mechanical system while achieving thermal stratification (stratified air distribution) that optimizes the performance of people and the building it serves.

The research focuses on the design, operation and maintenance of a UFAD system in a hospital. Moreover, the analysis presented in this study will convey valuable information for future research that will explore the various benefits of the application of UFAD in Hospitals.

List of Contents Chapter 1…………………………………………………………………………..…….....1 1.1. Aim…………………………………………………………………………..….…1 1.2. Objective.……………………………………………………………………..…...1 1.3. Scope……………………………………………………………………….……...1 1.4. Limitation..…………………………………………….…………………….….....1 1.5. Significance of Study....………………………………………..…………...……...1 Chapter 2. Literature Study……………………………………...…...………..………......2 2.1. Introduction…………………………………………………………………..…...3 2.2. Evaluation of UFAD Systems…………………………………….……………..10 2.3. Findings from Literature Study…………………………………………...……..12 2.4. Standards & Codes………………………………...…………………………….14 2.5. Methodology…………………………………………………….………………15 Chapter 3. Desktop Studies………………………………………………...……….…...19 3.1. Desktop Study 1…………………………………………………………...….....19 3.2. Desktop Study 2………………………………………………..………..……....22 3.3. Desktop Study 3…………………………………………….………...…….…...24 3.4. Market Survey……………………..…………………………………….….…...26 Chapter 4. Case Study…………….……………………………………………….….….27 4.1. Project Details……………………………………….………………………......27 4.2. UFAD Design Configuration…………………………….……………...…….....31 4.3. Maintenance & Operation……………………………….…………………........33 4.4. Findings & Observations………………………………...…………………........34 Chapter 5. Proposal…………….……………………………………………..…….…....35 5.1. Area of Study……………………………………….…………………………...35 5.2. Project Details…………………………….…………………..............................36 5.3. UFAD Configuration……………………………….…………………................48 5.4. Computational Fluid Dynamics (CFD) Analysis………………………………..51 5.5. Construction & Commissioning……………………….…………………….......61 5.6. Controls, Operation & Maintenance…………………………..………………...65 5.7. Life Cycle Cost (LCC) Analysis…………...……….……………………….......72 5.8. UFAD & Sustainable Green Buildings………………..…………………….......74 6.0. Conclusions…………….…………………………………………………….….…..80 7.0. References…………….…………………………………………..………….….…..81 8.0. Annotated Bibliography…………….……………………………………….………82

List of Figures Figure 1 Conventional overhead air distribution………………………………..….….......5 Figure 2 Underfloor air distribution (UFAD) system……………………………....….......6 Figure 3 IAQ with conventional overhead air distribution……………………..…….........8 Figure 4 IAQ with underfloor air distribution……………………………….…………….9 Figure 5 Room air stratification………………………………..……………..………........9 Figure 6 UFAD System Working………………………………………………..……......11 Figure 7 Effect of room airflow……………………………………………………….…...12 Figure 8 Raised Access Floor Components………………………...………………..…...17 Figure 9 Typical Common Area…………………………………………………….…....20 Figure 10 Typical Cubicle……………….……………………..…………………............20 Figure 11 Typical Perimeter Office……………………………………................................20 Figure 12 System Configuration…………………………………………………..….......20 Figure 13 Schematic 6th-floor plan………………………………………………….........23 Figure 14 Mote placement in diffusers…………………………………............................23 Figure 15 UFAD in patient ward…………………………………….………………........25 Figure 16 UFAD in corridor…………………………………………………………........25 Figure 17 UFAD in lift lobby……………………………………......................................25 Figure 18 UFAD in lounge…………………………………………..................................25 Figure 19 UFAD Components……………………………………….................................26 Figure 20 Project Renders………………………………………………………...…........27 Figure 21 Project Map……………………………………………………………….........27 Figure 22 Project Key Plan………………..……………………………...........................28 Figure 23 Yearly Windrose Analysis…………………………………………...…..…......29 Figure 24 Annual Sun Path Analysis of the Site………………………………….............29 Figure 25 Massing and Zoning………………………..……………………………..........30 Figure 26 Project Features…………………………………………………………..….....30 Figure 27 Typical Office Interiors…………………………………….………………......31 Figure 28 Round Swirl Flow Diffuser…………………………………………….…........31 Figure 29 Linear Perimeter Diffuser……………………………………...........................31 Figure 30 Damper opened……………………………..…………………………..….......31 Figure 31 Damper closed……………………………………………................................31 Figure 32 Zone Thermostat…………………………..……………………………...........31 Figure 33 Return Air Grille……………………..…………………………………..….....31

Figure 34 Suction Cap…………………….………………………………………...….....32 Figure 35 Underfloor plenum…………………………………………………………......32 Figure 36 Installation of diffusers………………………………………………..…….....32 Figure 37 Typical UFAD System Working……………………………………….............32 Figure 38 Fan Powered Non-Pressurised plenum system……………………...………....33 Figure 39 UFAD Passive Components…………………………………………................33 Figure 40 AHU Room………………………..…………………………….......................33 Figure 41 Project Renders…………………………………………………………...........36 Figure 42 Project Map…………………………………………………………...……......36 Figure 43 Project Key Plan……………………………………………………...……......36 Figure 44 Annual Sun Path Analysis of the Project………………………………...….....38 Figure 45 Annual Windrose Diagram……………………………………….....................38 Figure 46 Building Materials in Standard and Energy Efficient Design Case…………...38 Figure 47 E-20 Calculation sheet of Standard Design Case………………………….......41 Figure 48 E-20 Calculation sheet of Energy-Efficient Design Case………….………..…42 Figure 49 Tonnage in various design cases……………………………….........................46 Figure 50 Typical HVAC Equipment Range……………………………….......................47 Figure 51 Typical HVAC Equipment Setup………………………………………...….....47 Figure 52 Estimated Cooling Tower Water Usage……………………………………......50 Figure 53 Emergency Room Model for UFAD CFD…………………………………......51 Figure 54 UFAD Diffuser Flow and Swirl Angle Considerations……………………......51 Figure 55 Plan Views of Diffusers Swirl Flow Movement………………………...……..52 Figure 56 3D Views of Diffusers Swirl Flow Movement……………………….…..........52 Figure 57 Sectional Views of Diffusers Swirl Flow Movement……………………….....53 Figure 58 Plan View of Surface Temperature Plots…………………………....................53 Figure 59 3D View of Surface Temperature Plots…………………..................................53 Figure 60 Temperature Contour Plot at 0.70m Height……………………………............54 Figure 61 Temperature Contour Plot at X-Plane……………………………………….....54 Figure 62 Relative Humidity Contour Plot at 0.70m Height………………………..........54 Figure 63 Plan View of Airflow Lines……………………................................................55 Figure 64 3D View of Airflow Lines……………………………......................................55 Figure 65 Typical Airflow lines near patient……………………………………………...55 Figure 66 Thermal Comfort Index in Plan View…………………………………….........56 Figure 67 Thermal Comfort Index in 3D View……………………………………….......56 Figure 68 Thermal Predicted Mean Value (PMV)………………...……………………...56

Figure 69 Room Air Stratification……………………………………..............................57 Figure 70 Room Air Stratification at Plenum Level…………………………...………....57 Figure 71 Room Air Stratification at Feet Level…………………………………...….....57 Figure 72 Room Air Stratification at Sill Level…………………………………….........57 Figure 73 Room Air Stratification at Body Level……………………………………......58 Figure 74 Room Air Stratification at Head Level……………………………...................58 Figure 75 Room Air Stratification at Ceiling Level…………………………………........58 Figure 76 Reception / Waiting Area………………………………..…………………......59 Figure 77 Emergency Room……………………………………………............................59 Figure 78 Underfloor Plenum Pedestals…………………………………………..............59 Figure 79 VAV Fan Pressurized Diffuser……………………………………....................59 Figure 80 Accounts / Office Room…………………………………………………….....59 Figure 81 Doctor Consultation Room……………………………….................................59 Figure 82 Physiotherapy Room…………………………...................................................59 Figure 83 Canteen………………………………………………..………………...…......59 Figure 84 Pharmacy………………………………………………..…………………......60 Figure 85 Conference Room…………………………………………………….……......60 Figure 86 Staff Room…………………………………………………………..................60 Figure 87 Corridor………………………………………………………….......................60 Figure 88 Isolation Ward……………………………………………………….................60 Figure 89 Operation Theater…………………………………….......................................60 Figure 90 Example sequence for controlling thermal stratification…………………........67 Figure 91 Savings in energy usage…………………………………..................................78 Figure 92 Savings in water usage………………………………………………………....78 Figure 93 Savings in material usage………………………………...................................79

List of Tables Table 1 Comparative Analysis of UFAD & OHAD………………………….......................8 Table 2 RAF Technical Specifications……………………………………………….........26 Table 3 Yearly Dry Bulb Temperature of Hyderabad…………………………….…..........29 Table 4 Yearly Dry Bulb Temperature of Hyderabad…………………...............................37 Table 5 Door Schedule………………………………………………………….................39 Table 6 Window Schedule………………………………………………………………....39 Table 7 Heat Load Summary of Energy Efficient Design Case……………….……..........43 Table 8 Energy Efficient Design Case Considerations for Ground Floor………………....44 Table 9 Energy Efficient Design Case Considerations for First Floor…………….............45 Table 10 AHU capacities of each zone………………………………................................46 Table 11 Material Specifications……………………………………..……..………..........48 Table 12 LCC Comparison of OHAD & UFAD………………..…………........................72 Table 13 LEED credits that could be achieved with UFAD systems…………….…..........74

List of Abbreviations ACH

Air Changes Per Hour

AHU

Air Handling Unit

ANSI

American National Standards Institute

ASHRAE

American Society of Heating, Refrigerating and Air-Conditioning Engineers

CAV

Constant Air Volume

CFD

Computational Fluid Dynamics

CFM

Cubic Feet Per Minute

CHW

Chilled Water

COP

Coefficient of Performance

DBT

Dry Bulb Temperature

FFL

Finished Floor Level

FM

Facility Management

GPM

Gallons Per Minute

HVAC

Heating, Ventilation & Air-Conditioning

IAQ

Indoor Air Quality

IGBC

Indian Green Building Council

ISHRAE

Indian Society of Heating, Refrigerating and Air-Conditioning Engineers

LCC

Life Cycle Cost

LEED

Leadership in Energy and Environmental Design

NBC

National Building Code

NFPA

National Fire Protection Association

OHAD

Over Head Air Distribution

O&M

Operation & Maintenance

PMV

Predicted Mean Value

RAF

Raised Access Floor

SAT

Supply Air Temperature

SHGC

Solar Heat Gain Coefficient

SSL

Structural Slab Level

TAC

Task Ambient Conditioning

TR

Ton of Refrigeration

UFAD

Under Floor Air Distribution

UPS

Uninterruptible Power Supply

VAV

Variable Air Volume

WBT

Wet Bulb Temperature

WWR

Window-Wall Ratio

Chapter - 1 1.1. Aim To create an integrated, straightforward, and efficient mechanical system while achieving thermal stratification (stratified air distribution) through an Underfloor Air Distribution (UFAD) system that optimizes the performance of people and buildings while reducing life cycle costs.

1.2. Objectives The research objectives of this project are: ● To improve ventilation efficiency and Indoor Air Quality (IAQ) by reducing the distribution of pollutants within the building. ● To improve occupant comfort, productivity and health by achieving thermal stratification. ● To reduce building life cycle costs.

1.3. Scope This project's scope is to incorporate an Underfloor Air Distribution (UFAD) system in a Hospital (Institutional) building. Underfloor air distribution is commonly used in office buildings, particularly highly reconfigurable and open-plan offices with raised floors. UFAD is also common in command centers, IT data centers and Server rooms that have large cooling loads from electronic equipment. The ASHRAE Underfloor Air Distribution Design Guide suggests that any building considering a raised floor for cable distribution (Airports, Industries, offices, hospitals, recreation, laboratories, etc) should consider UFAD.

1.4. Limitation This research is limited to presenting the results of an experimental and practical application of underfloor air distribution (UFAD) system in a Hospital building with a composite climate.

1.5. Significance of Study There are fewer practices of underfloor air distribution because of a lack of information and design guidelines. The number of applications in healthcare facilities is even lower. Through this research, the construction industry realizes promoting the use of UFAD, especially in the healthcare sector.

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Chapter-2: Review of Literature Various sources and search engines were used to find the literature by using specific keywords to search for the relevant reports or browsing through the list of documents. First, the references from the book “Underfloor Air Distribution (UFAD) Design Guide” by Fred S. Bauman were used to start searching the literature. His references include papers, articles, and web references presenting major contributions to the understanding and development of UFAD technology and design. Other literature search methods were utilized. Below is the list of sources: ASHRAE abstract archives: ASHRAE transactions and journal papers are the main sources of the UFAD systems.

Center for the Built Environment (CBE): The Center for the Built Environment (CBE) at UC Berkeley is a National Science Foundation Industry/University Cooperative Research Center. UFAD, as one of the HVAC systems, is the topic of the center and published many papers. The main authors are F. Bauman and T. Webster.

Building Diagnostics Research Institute: Dr James Woods “What Real-World Experience Says About the UFAD Alternative” The search engines and publication lists are: ● ASHRAE abstract archives (1980-1997) ● ASHRAE Bookstore ● ScienceDirect (ELSEVIER journals) ● UMI Digital Dissertations ● Wilson Abstracts

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2.1. Introduction 2.1.1. Research Background The Underfloor Air Distribution (UFAD) system was traditionally designed to serve data centers since the year 1950. The application of the UFAD system was then extended for human comfort in the 70s. Although this air distribution technology has been available for decades, there was no comprehensive guide or standards available to support the development of this technology. Until recent years, ASHRAE Handbook HVAC Application (ASHRAE, 2015) and various standards such as ASHRAE Standard 62.1, 113 have been amended to include the UFAD system (ASHRAE, 2013b, 2013c). ASHRAE then published a UFAD guide on the design, construction and operation of underfloor air distribution systems in the year 2013 due to its wide application in North America (ASHRAE, 2013d). This guide is a comprehensive compilation of information supported by decades of extensive research results It is designed to provide architects, design engineers, building owners and building facility teams with a complete understanding of the system. The guide is continuously updated with the latest research findings in the development of this technology.

According to the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 55, human thermal comfort is that condition of mind that expresses satisfaction with the thermal environment. In terms of body sensations, thermal comfort is a sensation of hot, warm, slightly warmer, neutral, slightly cooler, cool and cold. To design high energy efficiency with human comfort HVAC systems, it is necessary to gather detailed information about the behaviors of the airflow in both the spaces and rooms of the building.

Thermal comfort and indoor air quality (IAQ) are the two important factors in indoor environmental quality that are related to heating, ventilating and air conditioning (HVAC) systems. The concept of air distribution in the UFAD system is different from the conventional overhead air distribution (OHAD) system. Thus, the temperature control, air movement and air contamination distribution in the occupancy space are different.

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2.1.2. Underfloor Air Distribution System An underfloor air distribution (UFAD) system is an HVAC system that uses the open space (underfloor plenum) between the structural slab and the underside of a raised floor to deliver conditioned air to supply outlets located at or near floor level within the occupied zone (up to 6 ft). Since air is supplied in much closer proximity to the occupants than in conventional overhead systems, supply air temperatures must be higher (e.g., 60 ºF to 65 ºF).

UFAD systems are the same as conventional overhead systems in terms of the types of equipment used at the cooling and heating plants and primary air-handling units (AHU). The concept of underfloor air is not new, however, changes in building space usage, sustainable design and indoor air quality issues have sparked considerable recent interest in the concept.

This practice has proven to be an effective method of delivering conditioned air to localized diffusers in the occupied zone of the building.

Underfloor air distribution uses the area below a Raised Access Floor (RAF) system as an air supply plenum to deliver conditioned air throughout the space to floor-mounted diffusers.

The combination of a Raised Access Floor (RAF) and a well-designed Underfloor Air Distribution (UFAD) system, is one of the best environmental control systems for many types of buildings. These are becoming more popular around the world and particularly so in India.

Usually, a task/ambient conditioning (TAC) system is used with the UFAD system to allow individuals to control thermal conditions in small and localized zones. The concept of task/ambient conditioning (TAC) was developed to address many of the problems and concerns. TAC systems allow ambient air-conditioning requirements to be reduced in noncritical areas. Individually controlled diffusers provide task conditioning only when and where it is needed to maintain occupant comfort. In contrast to the centralized approach in which a large zone of the building is controlled by a single wall thermostat, the TAC system concept approaches the optimal solution of providing a collection of many small control zones (e.g., workstations), each under the control of an ideally located and calibrated “human” thermostat. In addition, by delivering fresh air in the near vicinity of the occupants, TAC systems are more likely to provide improved air movement and preferential ventilation in the occupied zone, as compared to conventional mixing type air distribution systems.

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2.1.3. UFAD System Description For purposes of introducing the concept of an underfloor air distribution system, it is instructive to identify how these systems differ from conventional ceiling-based air distribution systems. Figures 1 and 2 show schematic diagrams of an overhead system and a UFAD system, respectively, for a cooling application in a building.

Figure 1. Conventional overhead air distribution (4)

Historically, the approach to HVAC design in commercial buildings has been to supply conditioned air through extensive duct networks to an array of diffusers spaced evenly in the ceiling. As shown in Figure 1, conditioned air is both supplied and returned at ceiling level.

Ceiling plenums are typically quite large to accommodate the large supply ducts that must fit through them. Return air is most commonly configured as a non-ducted ceiling plenum return. Often referred to as mixing-type air distribution, conventional HVAC systems are designed to promote complete mixing of supply air with room air, thereby maintaining the entire volume of air in the space (floor-to-ceiling) at the desired setpoint temperature and ensuring that an adequate supply of fresh outside air is delivered to the building occupants.

This control strategy provides no opportunity to accommodate different thermal preferences among the building occupants or to provide preferential ventilation in the occupied zone.

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Figure 2. Underfloor air distribution (UFAD) system (4)

With UFAD systems, conditioned air from the air handling unit (AHU) is ducted into the underfloor plenum where it typically flows freely to the supply outlets. Underfloor systems are generally configured to have a relatively large number of smaller supply outlets, many in close proximity to the building occupants, as compared to a conventional overhead system.

Outlets may be floor diffusers, as shown in Figure 2, or, particularly when part of a task/ambient conditioning (TAC) system, desktop or partition outlets equipped with individual control. If the outlets are adjustable, this arrangement provides an opportunity for nearby occupants to have some amount of control over thermal comfort conditions in their local environment. Air is returned from the room at ceiling level (un-ducted plenum return is shown). This produces an overall floor-to-ceiling airflow pattern that takes advantage of the natural buoyancy produced by heat sources in the office and more efficiently removes heat loads and contaminants from the space, particularly for cooling applications. In contrast to the well-mixed room air conditions of the conventional overhead system, stratification is actually encouraged above the head height where increased temperatures and higher levels of pollutants will not affect the occupants.

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2.1.4. Comparative Analysis of Underfloor Air Distribution (UFAD) and Conventional Overhead Air Distribution (OHAD): UFAD systems are similar to conventional overhead systems in terms of the types of equipment used at the cooling and heating plants and primary air-handling units (AHU). Key differences arise with UFAD systems in their use of an underfloor air supply plenum, warmer supply air temperatures into the room, delivery of air in the near vicinity of occupants (with or without individual control) and the resulting floor-to-ceiling airflow pattern, and the solutions used for perimeter systems. To successfully employ a UFAD system, the implications of these differences must be considered, starting at an early stage in the design process.

Comparison Base

Underfloor Air Distribution System

Conventional Overhead Air Distribution System

Floor pressurization

The floor is entirely pressurized.

The ceiling area is not pressurized. Ducts reach each diffuser/grill.

Diffuser

Diffusers put on the false floor tiles with a control damper.

Diffusers are put on the false ceiling tiles with control dampers.

Electrical works

Electrical cable runs along either below the false floor or within the pressurized floor.

Electrical cable runs above the false ceiling.

Leakage of the air

If there is a leakage in the false floor, it may cause a loss of cool air.

Cool air moves inside ducts, so even if there is a gap in the ceiling, no loss of cool air.

Cost - Duct

The ducting quantity is less as fewer ducts are used.

Ducting quantity is more as more ducts are used.

Cost - Diffuser

One diffuser may cost Rs. 6000/-

One diffuser may cost Rs. 2000/-

Running cost

Cooling will be achieved soon.

In case of a 12-hour operation, the Unit will be run one hour less for pre-cooling.

20% more efficient.

Cooling will be achieved late.

In case of a 12-hour operation, the Unit will be run one hour more for pre-cooling.

Cost - Underdeck Insulation

Under deck, insulation is not required on the top floor.

Under deck, insulation is required on the top floor. Rs. 65/- per sft.

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Cost - flooring

False flooring costs more.

Ranging from Rs. 250/- to Rs. 800/- per sft.

No false flooring is required for the HVAC system. For electrical, raceways, trenching can be done.

Modification

Modification is easy as we have to simply move the tile.

Modification is difficult as the duct also has to be replaced with light every time.

Ceiling Height

Less ceiling height is required as there is no duct.

Need 500mm above the false ceiling to accommodate duct.

Construction time

40% faster construction time.

Relatively slower construction time.

Supply Air Temperature

~60 to 68°F supply air

~50 to 55 °F supply air

Return Air Temperature

~77- 85°F, room temperature is higher at ceiling level.

~75 °F, almost the room air temperature.

Air Delivery

Air is delivered at low velocity and heat sources drive air motion via thermal plume.

Ceiling diffusers provide high-velocity supply air throw.

Table 1. Comparative Analysis of UFAD & OHAD

2.1.5. IAQ with Conventional Overhead Air Distribution:

Figure 3. IAQ with conventional overhead air distribution (5)

In a conventional overhead system, all the supply air is injected high in the space, at a velocity designed to create mixing with the room. Then some of the mixed air is drawn off, usually at ceiling level, as a return or exhaust air. Thus, pollutants and germs must be disseminated throughout the room, they are actively spread and shared between all room occupants.

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2.1.6. IAQ with Underfloor Air Distribution: UFAD stratifies the air and prevents mixing. Pollutants are carried upwards, in thermal plumes, out of reach of occupants. Concentrated pollutants are removed via exhaust at the highest points in the room. Occupants located in clean zones constantly breathe uncontaminated air. No sharing of pollutants and germs between occupants.

Figure 4. IAQ with underfloor air distribution (5)

Stratified zone: Stratification refers to a non-uniform temperature throughout a zone, with higher temperatures towards the ceiling and lower temperatures towards the floor. In a stratified room, return air is warmer and has a higher level of contaminants than supply air does.

Figure 5. Room air stratification

Occupied zone: The occupied zone refers to the space in a room that begins one foot from all walls and extends from the floor to six feet above the floor. Mixing the occupied zone instead of the whole space can result in energy savings in spaces with high ceilings.

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2.2. Evaluation of UFAD Systems 2.2.1. Benefits and Barriers of UFAD Systems (Bauman, 2003) [2]: The general benefits of a UFAD system were outlined by Bauman as follows: ● Improved thermal comfort: By allowing individual occupants to control their local thermal environment. ● Improved ventilation efficiency and indoor air quality: 20-50% better ventilation as recognised by ASHRAE 62.1 by delivering the fresh supply air at floor level or near the occupant. ● Reduced energy use: Saves more than 20% of energy while achieving thermal comfort to the occupant. ● Significantly reduced life-cycle building costs: Due to reduced expenses and annual energy usage. ● Reduced floor-to-floor height in new construction: By reducing the overall height of the service plenum, 0% of space is wasted. ● Faster construction time: 40% faster construction time compared to the conventional air-conditioning system. ● Flexibility: Flexibility for relocating wiring, piping, and other building services. The raised access floor (RAF) system is 100% flexible and can be changed as per the requirement. ● Improved productivity and health: UFAD maintains occupant comfort while maintaining proper IAQ levels and eliminating airborne infections.

While there are many advantages of UFAD systems over traditional overhead systems, there are still some barriers to the adoption of UFAD systems. These barriers are ● New and unfamiliar technology: Lack of familiarity can create problems throughout the entire building design, construction, and operation process. ● Lack of information and design guidelines: There has not previously existed a set of standardized design guidelines for use by the industry. ● Whole-building performance: No whole-building energy simulation program is capable of modeling a UFAD system.

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● Higher initial costs: Typically, a UFAD installation requires a $5 to $8 per sq. ft. premium over comparable overhead systems. ● Cold feet and draft discomfort: Poorly designed (e.g., the close proximity of supply outlets to the occupants) and operated UFAD system can cause cold floor problems. To prevent this problem, all office floors are recommended to be carpeted. ● Spillage and dirt entering UFAD systems: There is a probability of spillage and dirt entering directly into the underfloor supply airstream. Most floor diffusers, however, have been designed with a catch-basin (e.g., to hold the liquid from a typical soft drink spill).

2.2.2. UFAD System Working: Once the air enters through the floor diffusers, it spreads across the floor forming a reservoir of fresh cool air. Any sources of heat (e.g. people computers etc.) will generate a thermal plume rising upward entraining the surrounding air, as shown in Figure 6. The fresh cool air at floor level will flow to replace that which is warmed and lifted into the convective plumes.

This means the fresh air continuously replaces the air as it is used and contaminated air is lifted to a high level for removal from the space.

Figure 6. UFAD System Working (9)

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2.3. Findings from Literature Study In UFAD systems, thermal stratification is one of the most important criteria that reduce energy consumption and improve ventilation efficiency. Thermal stratification is produced in a properly designed and controlled UFAD system during cooling operation. In order to achieve thermal stratification, the airflow distribution and momentum from the floor diffusers are the key elements.

Stratification Issues: Controlling Stratification (Webster, 2002) [8] According to ASHRAE Standard 55-1992 (ASHRAE 1992), the vertical air temperature differences in the interior zone is limited to 5 ºF. Recent laboratory experiments show the thermal stratification performance of UFAD systems (Webster et al. 2002a, 2002b). Figure 7 shows the impact of variations in total room airflow on stratification for swirl diffusers operation in a simulated interior space with a total heat input of 18 Btu/h-ft² and a supply air temperature of 64 ºF. This temperature profile demonstrates the sensitivity to changes in airflow rate. According to this figure, the first profile presents the space as “over-aired,” while the last profile shows that the head-foot temperature difference has increased to 6.8 ºF, exceeding the limit of 5 ºF.

Figure 7. Effect of room airflow variation at constant heat input, swirl diffusers, interior zone.

(Bauman, 2003) (1)

To improve energy performance (reduce airflow) while maintaining thermal comfort (avoiding excessive stratification), the middle profile at a flow rate of 0.6 cfm/ft² could be a reasonable target. In this experiment, the flow rate at 0.6 cfm/ft² still satisfies the limitation of vertical temperature differences (5F) with 40% less air than the first profile.

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UFAD is a widely accepted concept of air distribution globally and has various advantages compared with the overhead air distribution system. There might be a slightly more initial cost but the running cost is low and has a return of investment over a period of time.

The performance of an occupant-controlled floor-based task conditioning system configured to ● Overall performance of the floor-based system, ● It is recommended to reduce the maximum airflow rate of the floor supply module below 190 cfm, and ● By controlling supply volume, the floor-based system can be operated to maintain acceptable thermal comfort.

The three strategies for capturing as many benefits of underfloor air distribution as possible while keeping the initial cost to a minimum are 1. Minimize the ductwork in the plenum: for flexibility (reconfiguration of the room) reason. To use multiple vertical shafts serving a single plenum.

2. Prevent plenum leakage: Carefully seal raised access panels and window-wall connections to the slab at stair landings and air highways.

3. Don’t oversize airflow: The airflow calculation for UFAD is different from the typical overhead system because the airflow calculation for UFAD needs to be broken into two parts (Two distinct room regions, occupied and unoccupied zone), while the airflow calculation for typical overhead system considers a single zone at steady state.

For the UFAD system, a separate energy balance equation can be written for each of the distinct zones.

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2.4. Standards & Codes Listed below are the applicable building standards and codes that have important provisions related to the design, installation, and operation of UFAD systems.

1. ANSI/ASHRAE STANDARD 55-1992: THERMAL ENVIRONMENTAL CONDITIONS FOR HUMAN OCCUPANCY [ASHRAE 1992] 2. ANSI/ASHRAE STANDARD 62-2001: VENTILATION FOR ACCEPTABLE INDOOR AIR QUALITY [ASHRAE 2001b] 3. ANSI/ASHRAE/IESNA STANDARD 90.1-2001: ENERGY STANDARD FOR BUILDINGS EXCEPT LOW-RISE RESIDENTIAL BUILDINGS [ASHRAE 2001c] 4. ANSI/ASHRAE STANDARD 113-1990: METHOD OF TESTING FOR ROOM AIR DIFFUSION [ASHRAE 1990] 5. ASHRAE STANDARD 129-1997: MEASURING AIR CHANGE EFFECTIVENESS [ASHRAE 1997] 6. TITLE-24: CEC SECOND GENERATION NONRESIDENTIAL STANDARDS [CALIFORNIA ENERGY COMMISSION 2001] 7. NFPA 90A: STANDARD FOR THE INSTALLATION OF AIR CONDITIONING AND VENTILATING SYSTEMS [NFPA 1999] Uniform Building & Other Applicable Codes: Local fire codes sometimes place restrictions on the size of open supply air plenums without any smoke breaks in the form of partitions separating the plenum into smaller zones. These fire codes may limit the total area (e.g., less than 3,000 ft² [280 m²]) and horizontal dimension in one direction (e.g., less than 30 ft [9 m]) of an unobstructed underfloor air supply plenum.

A typical underfloor plenum contains a low level of combustible materials; thus, in certain codes, plenums under 18 in. (45 cm) in height do not require sprinklers. The issue of whether sprinklers need to be installed in a plenum is contentious for a number of reasons. First, as electric cabling is typically the only source of fire risk, water is not the best source of fire suppression. Fundamentally, the codes governing underfloor plenums should be no different than those for ceiling plenums.

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2.5. Methodology 2.5.1. Three Basic Approaches of UFAD Systems: Currently, three types of UFAD systems are available. Bauman and Webster (2001) summarized these types in their paper. These are 1. Supply air delivered via passive floor registers and/or fan-powered terminal boxes supplied by a pressurized underfloor plenum and central air handler.

2. Supply air delivered via active, locally-controlled, fan-powered registers (in the floor or workstations), supplied by a very low-pressure underfloor plenum and central air handler, and 3. Supply air delivered via underfloor ducts to terminal devices or supply outlets.

2.5.2. Tools: 1) Physical Tools: 1. Floor Plenums: The space between the access floor and the structural floor is the floor plenum. Using this space as an air distribution plenum requires some special considerations. First, the floor panel seams must provide a tight seal to prevent air leakage from the plenum into the space. In some cases, ductwork is run through the space to special variable load areas and the space may need partitioning for life safety or thermal zoning. A typical underfloor plenum is between 12 and 18 inches in height.

2. Diffusers (Supply & Return): Room air distribution is accomplished through one of two types of floor diffusers. Interior spaces are controlled through a system of adjustable passive floor-mounted diffusers. Each diffuser consists of an adjustable swirl plate located in a mounting basket and mounts through a hole cut in the concrete floor panel. The basket catches any dirt or spilt liquids and prevents contamination of the space below the floor. The adjustable swirl plate allows the occupants to adjust their diffusers to a comfortable level in their space. The diffusers are designed to achieve mixing of the approximately 65 F degree supply air within a very tight radius of the diffuser and at a low velocity. Typical diffuser airflow is about 60 to 100 CFM per diffuser.

The second type of diffuser is used with underfloor mixing boxes and perimeter fan coil units. This rectangular grille is used to provide an air curtain washing exterior surfaces with Application of Underfloor Air Distribution in Hospital Building

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warm or cold air. These grilles depend on much higher velocities and can be used in various lengths to match the airflow requirements of the mixing box or fan coil unit. Either a 0° or 15° deflection blade can be used to provide the required throw pattern.

3. Grills: A grille is a perforated cover for an air duct (used for heating, cooling, ventilation, or a combination thereof). Grilles sometimes have louvers that allow the flow of air to be directed.

A register differs from a grille in that a damper is included.

4. Fan coil units: These are another option to handle spaces with variable load patterns and are well suited to addressing the heating requirements of perimeter zones. Available in size from 325 to 2800 CFM these fan coil units also fit underfloor in the space between pedestals and the grids of the access flooring system. Heating is provided in these with either a hot water coil or an electric heater.

5. Air Handling Units (AHU’s): AHU's supply fresh air to the room. It takes air from the outside, filters it and reconditiones it (cooled by a cooling coil or heated by a heating coil). Where hygienic needs for air quality are lower, the air from the rooms can be re-circulated for energy-saving purposes.

6. Ducts (Supply & Return): Ducts are conduits or passages used in heating, ventilation, and air conditioning (HVAC) to deliver and remove air. The needed airflows include, for example, supply air, return air, and exhaust air. Ducts commonly also deliver ventilation air as part of the supply air. As such, air ducts are one method of ensuring acceptable indoor air quality as well as thermal comfort.

7. Dampers: Duct Damper or Volume Balancing Damper is a movable plate, situated in the ductwork that regulates the flow of air and redirects it to specific places of space. The usage of dampers is typically seen in zoning or zone control systems.

8. Raised Access Floor Panels: Raised access flooring uses modular floor panels which are suspended over the actual floor by a series of supports. This results in an empty space between the raised floor panels,

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typically called a plenum, which can be used to route building services such as plumbing, wiring, and HVAC instead of above a suspended ceiling.

Figure 8. Raised Access Floor Components (5)

9. Pedestals: Access floor pedestals are vertical structures that support the raised floor panel. These are adjustable fixtures that can be adapted to suit your access flooring requirements. Each pedestal is bonded to the substrate floor using an epoxy resin-based adhesive which can be strengthened by mechanical fixing.

2) Software Tools: 1. UFAD Design Tool by CBE (Center for Built Environment) UFAD Design Tool can achieve results from inputs of the design and optimizes interior zone and perimeter zone.

2. Microsoft Excel: Microsoft Excel Tool features calculation, pivot tables, and graphing tools. It is used for manual calculation of cooling in a cooling load estimation spreadsheet.

3. AutoCAD: AutoCAD is computer-aided design software that allows to draft, annotate and design 2D geometry and 3D models with solids, surfaces and meshes objects more quickly and easily.

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4. Autodesk Revit: Revit allows users to design a building and structure and its components in 3D, annotate the model with 2D drafting elements, and access building information from the building model's database.

5. Autodesk Computational Fluid Dynamics (CFD): Computational fluid dynamics (CFD) methods are used to predict the fluid flow, thermal comfort conditions of occupants, IAQ, and energy consumption.

6. Enscape: Enscape is a real-time rendering software that plugs directly into the modeling software and gives an integrated visualization and design workflow.

7. Edge Buildings Tools: EDGE software offers a measurable way to cut back on the resource intensity of the building design.

2.5.3. UFAD Step by Step Design Procedure: 1. Initial building design considerations.

2. Selection of system configuration.

3. Determine space cooling loads.

4. HVAC Zoning.

5. Determining ventilation air requirements.

6. Determining zone supply air temperature and flow rate.

7. Determining return air configuration.

8. Calculating cooling coil load.

9. Duct layouts and plenum configuration.

10. Selection of primary HVAC equipment.

11. Select and locate diffusers.

12. Develop a control strategy.

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Chapter-3: Desktop Studies 3.1. Desktop Study 1: ➔ Project Details: Project Name: FNBO Technology Center Project Location: Omaha, U.S.A Market: Technology Center Size: 3 stories (200,000 ft²) ➔ Project Description: The Technology Center houses the corporate offices and check processing center for the First National Bank of Omaha. The building is occupied 24/7. Under normal operations, it is expected that 500 people will occupy it. ➔ UFAD Design Configuration: ● Plenum Height: 0.46 m (18 in.) in all areas except computer and card processing areas which are 0.61 m (24 in.). ● Diffuser Type: Constant volume swirl diffusers plus active fan-powered diffusers, with linear bar grille diffusers. ● Raised Floor: 600 x 600mm concrete-core panels using a stringer-less post mounting system. ● Supply Air Temperature: Nominal 17°C (63°F), varies with load.

HVAC systems: Conditioned air is supplied through fourteen modular packaged air-handling units (AHU’s) located within the top-level mechanical penthouse area and a ground-level mechanical room. Constant volume and variable temperature systems are used to serve the computer and equipment-intensive areas of the building. Variable volume systems with hot water reheat are provided to serve the more standard office areas throughout the building. The forced air systems maintain space and overall building pressurization to control airflow and contaminate movement within the building.

Air is delivered from the pressurized underfloor plenums into the space through three types of diffusers. In computer environments and equipment spaces typical perforated raised access floor panels are used.

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Figure 9. Typical Common Area

Figure 10. Typical Cubicle

Figure 11. Typical Perimeter Office, showing fan-powered rectangular grille, and passive floor diffuser.

Approximately half of the panels have adjustable dampers to accommodate airflow balancing.

In open/common areas with carpeted access flooring, heavy-duty rectangular floor registers are provided. Small round floor diffusers are used to serve individual cubicle workspaces.

Figure 12. System Configuration Application of Underfloor Air Distribution in Hospital Building

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The majority of spaces served by the underfloor air distribution systems are open-plan areas.

However, the enclosed private offices at the perimeter require special attention due to varying loads. Conference rooms and perimeter offices are equipped with fan-powered rectangular diffusers located on the interior side of the room in addition to the passive (no local fan) round floor diffusers. In the underfloor areas, typical ceiling return air grilles are used. Hydronic radiant ceiling panels provide heating in perimeter areas. Fan-powered diffusers are also provided at high heat-producing equipment (large production laser printers) to deliver spot cooling from the underfloor supply plenum.

UFAD System Performance: Facility management (FM) personnel prefer the simplicity of the UFAD system and the fact that it has fewer active mechanical components to service than the overhead VAV systems. ➔ Findings: ● Interior Diffusers: Many interior diffusers were located too close to occupants.

However, it was considered to be too much effort to move the panels because of the necessity of working with glued down carpet tiles. Therefore, most diffusers located in cubicles were either shut off or reduced to about 20% flow. Leakage from electrical floor plates in many cases was enough to compensate for the reduced diffuser flow, along with aisle diffusers that were left at full flow. Reducing the overall airflow may ameliorate the low stratification that was found during initial operation. Furthermore, it is not clear how the use of linear diffusers in the aisles impacts room air distribution.

These diffusers generally have lower induction rates than swirl diffusers and the effect of this on stratification performance is not well understood.

● Diffuser Adjustment: The FMs do not encourage occupants to adjust diffusers.

However, since there are multiple shifts some diffusers are adjusted frequently due to individual differences. The diffusers can get stuck due to dirt, which makes adjustment difficult. In other cases, the diffuser flow plates were too loose usually due to the baskets having been removed.

● Ductwork: The extensive use of ductwork in this design seems to be a conservative solution, at least for the plenum supply. This extensive ductwork reduces the fan energy savings potential for UFAD systems.

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3.2. Desktop Study 2: ➔ Project Details: Project Name: EPA Region 8 Headquarters Project Location: Denver, Colorado Gross Sq.ft: 418,300 ➔ Project Description: The EPA building is a 9-story structure with an area listed as 418,300 Gft². Completed and occupied in December 2006, the building includes 292,000 Gft² of non-retail office space, 56,000 ft² of ground-level retail, and 104,100 ft² of underground parking. It has approximately 800 EPA employees and contractors occupying the office space. ➔ UFAD Configuration: The first three floors of the building are served by an overhead air distribution system, while floors 4-9 are conditioned by an underfloor air distribution (UFAD) system.

The interior zones of the floor plate are served by swirl diffusers located in workstations and aisleways. There are roughly 240 of these diffusers on a typical floor plate such as the 7th floor. Airflow from these diffusers is controlled by the pressure setting in the supply plenum.

Occupants have some degree of control by manually adjusting the diffuser opening.

The figure shows a schematic plan of the 6th floor of approximately 29,239 Gft² of floor area.

The diagram shows the atrium centrally located on the north half of the floor plate. Also shown are two HVAC supply shafts, each serving four air highways that deliver and direct supply air into central regions of the open plenum. These shafts and air highways are shown in yellow on either side of the larger central return air shaft (shown in yellow). There are eight pressure sensors (small green circles) located in the large open underfloor plenum, each controlling the volume of air delivered by one of the eight supply air highways, as indicated, to maintain the desired plenum pressure setpoint. Each of these supply ducts contains an airflow measurement station.

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Figure 13. Schematic 6th-floor plan

Floor diffusers refer to the swirl diffusers located near or in each workstation. They generally control the interior temperature as discussed in the building description section above. They also can be considered a “user interface” to the system since they can be adjusted by the user to vary the airflow.

Figure 14. Mote placement in diffusers

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In terms of effectively conditioning the EPA building the UFAD system appears to operate very well. This conclusion is supported by the following findings.

Findings based on Occupant Satisfaction Survey: ● Occupant satisfaction with the UFAD system is positive. Occupants prefer UFAD over traditional systems. 75% of respondents preferred UFAD. ● Dissatisfaction with thermal comfort was very low at ~32%. Dissatisfaction with air quality was extremely low at 9-11%.

Findings based on Portable UFAD Cart Measurements: ● Room temperature is within ASHRAE standards. ● Stratification performance is acceptable although lower than optimal. ● Supply plenum performance is satisfactory.

Findings from leakage testing: ● Supply plenum leakage is low. Comprehensive testing that we conducted before the site visit showed Category 1 leakage to be negligible and Category 2 leakage (i.e., leakage to room) to be ~10% of floor peak design airflow.

3.3. Desktop Study 3: ➔ Project Details: Project Name: Tulsa Cancer Institute Project Location: Tulsa, Oklahoma Market: Healthcare Gross Sq.ft: 86,000 ➔ Project Description: Designed by Gensler’s Phoenix, AZ office, the Tulsa Cancer Institute is an exciting example of an innovative, well designed green medical office building. It is Oklahoma’s single largest medical facility built by a group of private physicians and the largest number of cancer specialists at one center. In addition to new technologies, the facility will also feature a wellness center, healing gardens, a mentoring area, and bright, open spaces. This $60 million project on 16 acres is aiming for LEED Silver for Environmental Design.

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➔ UFAD Configuration: Using nature as a healing element, this 86,000 sq ft. building comprises 72,000 sq. ft. of access floors with UFAD on two levels. The building’s two floors are arranged around three precise program features which center around a healing garden.

Figure 15. UFAD in patient ward

Figure 16. UFAD in corridor

● Plenum Height: 0.30 m (12 in.) ● Diffuser Type: Variable volume swirl diffusers. ● Raised Floor: 600 x 600mm calcium sulfate panels using a stringer-less post mounting system.

Figure 17. UFAD in lift lobby

Figure 18. UFAD in lounge

Findings based on Occupant Satisfaction Survey: ● Occupant satisfaction with the UFAD system is positive. Occupants prefer UFAD over traditional systems. A faster recovery rate has been reported with UFAD.

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3.4. Market Survey UFAD market has the most diverse products from grilles and diffusers to terminals and controls, as well as a variety of accessories.

The key market players for the global UFAD Systems market are listed below: ● AET Flexible Space ● Schneider Electric ● Price Industries ● Johnson Controls ● AirFixture ● Carrier ● Titus ● Trox ● DuctSox ● Tate Figure 19. UFAD Components

The detailed market survey on false flooring:

Table 2. RAF Technical Specifications

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Chapter-4: Case Study 4.1. Project Details: ● Project Name: Wipro IT SEZ ● Project Status: In Progress ● Market: Technology Center ● Client: Wipro Ltd. ● Architect: Morphogenesis ● Structural, MEPF & PMC: TATA Consulting Engineers Ltd. ● Contractor: Larsen & Toubro Ltd.

Figure 20. Project Renders

4.1.1. Site Analysis: ● Project Location: Gopanpally, Hyderabad, 501301. ● Latitude: 17°26'9.04"N ● Longitude: 78°17'56.42"E ● Number of Floors: 3B+G+15 ● Total Built-up Area: 10,00,000 ft² ● Total Plot Area: 16,00,000 ft² ● Future Expansion Area: 6,00,000 ft² ● Annual Energy Consumption: 2,994,576 kWh Figure 21. Project Map

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Figure 22. Project Key Plan

4.1.2. Project Description: Located in Hyderabad, spread across 101 acres of land, this corporate office for Wipro embodies the historical and cultural references of the region whilst being relevant to modern times. Gopanpally area is one of the preferred localities of infrastructure developments and has proximity to major IT hubs such as Gachibowli DLF Building, Hitec City Cyber Towers, Financial District, and Wipro Circle.

WIPRO's Gopanpally Campus is an IGBC gold certified green building that is the first-of-its-kind UFAD building in Hyderabad. It consists of 100,000 sqm of office space in the first development phase. The facilities will include additional amenities such as restaurants, gyms, cafeterias and a library. Relying on highly effective solar shading, the building can take advantage of a hybrid space conditioning approach using elevated airspeed within the offices. Low wall-to-window ratios and narrow floor plates ensure optimum daylight and low thermal absorption. The project is executed in earthy hues of clay bricks with low U-values thus making the façade energy efficient.

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4.1.3. Climate Analysis: ● Climate Condition: Composite Climate ● Summer DBT: 107 °F ● Summer WBT: 76 °F ● Winter DBT: 57 °F ● Mean Daily Range: 20 °F

Table 3. Yearly Dry Bulb Temperature of Hyderabad

The unique climate of the city makes it all the more comfortable for anyone to live in. It remains fairly warm throughout the year and generally does not receive much rainfall in the monsoon but due to the increase in global warming, even the finest place like Hyderabad has experienced very cold winters and heavy rainfall in very recent years.

Figure 23. Yearly Windrose Analysis

Figure 24. Annual Sun Path Analysis of the Site

A 3,000 sqm restaurant is located in the courtyard of the building complex. Comfort is maintained in this courtyard for a variety of conditions across Hyderabad’s three separate seasons; hot and dry, warm and humid, and warm and dry. The morphology adopted for the project is that of ‘disintegrated courtyards’.

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Rectangular volumes are stacked and rotated to create secondary courts whilst being planned around a central courtyard. All buildings are North-South orientated, and the East-West edges are kept open to enhance prevailing wind movements and natural ventilation.

Figure 25. Massing and Zoning

Figure 26. Project Features Application of Underfloor Air Distribution in Hospital Building

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4.2. UFAD Design Configuration: ● System Configuration: Conditioned air is distributed to diffusers across the entire floor area through a single, undivided pressurized open-plan plenum of 450mm (18 in.) height. Variable air volume (VAV) dampers are used to vary the supply air volume from zone thermostats. ● Diffuser Type: Variable volume round swirl floor diffusers of 10” diameter is used for interior zones, and linear bar grille diffusers are used for perimeter zones.

Figure 27. Typical Office Interiors

Figure 28. Round Swirl Flow Diffuser

Figure29. Linear Perimeter Diffuser Figure 30. Damper opened

Figure 32. Zone Thermostat

Application of Underfloor Air Distribution in Hospital Building

Figure 31. Damper closed

Figure 33. Return Air Grille

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● Raised Access Floor: 600x600mm calcium sulfate panels of 30mm thickness are used in AHU rooms and 28mm thick panels are used in office areas. Carpeting is provided in office areas to prevent plenum air leakage and to reduce the cold feet effect on the occupants. ● Pedestals: Adjustable aluminum tube pedestals with a diameter of 25mm are used.

Figure 34. Suction Cap

Figure 35. Underfloor plenum Figure 36. Installation of diffusers

4.2.1. UFAD System Working:

Figure 37. Typical UFAD System Working

● Air is delivered from the pressurized underfloor plenums into the space through two types of diffusers: round swirl floor diffusers and linear perimeter bar grille diffusers and electrical services were run under the plenum space.

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● The input of the VAV damper is connected to a thermostat and the output is connected to another VAV like a series connection. At the end of the connection, the output is connected to the power module. The power module gives 24V A.C supply to the system. The power module is then connected to the raw power and UPS. The thermostat then gives a command to the VAV damper to either open or close based on the room temperature. ● The airflow range of 6000cfm AHU of 10 TR capacity is used for a typical office area of 4000 sqft. The operation of AHU is quiet and is more efficient.

Figure 38. Fan Powered Non-Pressurised plenum system

Figure 39. UFAD Passive Components

Figure 40. AHU Room

4.3. Maintenance & Operation: ● The operation is flexible as the entire floor is a plenum, and HVAC reconfiguration and zoning are easier. ● UFAD system requires less energy to operate compared to the conventional system.

Typically, 20-30% of energy consumption is reduced by UFAD systems. Hence, there are more energy savings.

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● To eliminate spillage and dirt entering the supply air stream, the diffusers have been designed with catch-basins (dirt traps) and regular maintenance schedules have been adopted.

4.4. Findings and observations: ● In terms of effectively conditioning the Wipro building, the UFAD system appears to operate very well. ● The office adopted the simplicity of the UFAD system and has fewer active mechanical components to service than the overhead VAV systems. ● The UFAD system in the building is still in the testing phase as the building construction is in progress and there is currently no requirement for work from office jobs. ● The average supply air temperature in the plenum is 22 °C (72 °F). ● The average supply air temperature in the room is 23 °C (74 °F). ● The temperature difference maintained is between 71 °F to 76 °F and is as per ASHRAE comfort standards. ● The relative humidity maintained is 50% which lies between 25-60% as per ASHRAE standards. ● The temperature gradient from the floor to 6’ height (occupant zone) is 4 °F.

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Chapter-5: Proposal 5.1. Area of Study The field of research for this study is the Hospital (Institutional) Building.

Hospitals with UFAD type of ventilation have numerous benefits over the traditional overhead ventilation systems. Some of these advantages include structural flexibility, improved thermal comfort (controlling airborne infections), and ventilation efficiency amongst others.

Floor diffusers are used to supply conditioned air to the entire hospital building.

Designing and installing UFAD in hospitals requires the following three basic steps: ● Identify and specify the desired airflow pattern from the inlet to the outlet openings. ● Identify the main options which allow the desired airflow pattern to be achieved. ● Locate the openings which can be used so that the required ventilation rate can be delivered under normal circumstances.

A general procedure for underfloor ventilation in hospitals starts from the architectural design, ventilation system layout and component selection, vent sizing and designing ventilation control strategy. However, there is an urge to develop efficient and appropriate technologies and original architectural features to maximize the use of underfloor ventilation in hospitals. In addition to that, the costs of installation and durability of the ventilation systems should be addressed to encourage more hospitals to adopt this ventilation method.

5.1.1. Current Status of UFAD in India Underfloor air distribution (UFAD) has continued to gain popularity across the globe and particularly in India. The combination of a raised access floor system (RAF) with underfloor air distribution is a cost-effective solution for buildings with justifiable benefits over a conventional overhead system.

However, there are only a limited number of UFAD practices in India.

The higher initial costs and lack of information and design guidelines throughout the entire building design, construction and operation process have led to a lack of familiarity in India.

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5.2. Project Details: ● Project Name: Multispeciality Hospital Building (Hypothetical Building) ● Market: Healthcare

Figure 41. Project Renders

5.2.1. Site Analysis: ● Project Location: Kukatpally, Hyderabad, 500085. ● Latitude: 17.4964586° N ● Longitude: 78.4002286° E ● Number of Floors: B+G+1 ● Floor to Floor Height: 3600mm (12 ft) ● Total Built-up Area: 19,000 ft² / 1780 sqm ● Total Plot Area: 42,000 ft² / 3970 sqm

Figure 42. Project Map

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Figure 43. Project Key Plan

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5.2.2. Project Description: Located in Hyderabad, on 3970 sqm of land, this multispeciality hospital building will house the capacity of 100 beds.

Kukatpally is a suburb located in the northwestern part of Hyderabad in the Indian state of Telangana. It is one of the busiest business hubs in Hyderabad famous for its clothing and eateries. It has the largest density of population within Hyderabad with 33,076 persons per km2.

5.2.3. Climate Analysis: ● Climate Condition: Composite Climate ● Summer DBT: 107 °F ● Summer WBT: 76 °F ● Winter DBT: 57 °F ● Mean Daily Range: 20 °F

Table 4. Yearly Dry Bulb Temperature of Hyderabad

The unique climate of the city makes it all the more comfortable for anyone to live in. It remains fairly warm throughout the year and generally does not receive much rainfall in the monsoon but due to the increase in global warming, even the finest place like Hyderabad has experienced very cold winters and heavy rainfall in very recent years.

During summer, the maximum temperature is 43°C and the minimum is 14.5°C. It has 4 distinctive seasons, summer from May-September, spring from March to April (cool and average humidity), autumn for 2 months from October to November (hazy & dry), and winter from December to February (cold). The annual rainfall is 136.1 mm.

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Figure 44. Annual Sun Path Analysis of the Project

Figure 45. Annual Windrose Diagram

5.2.4. Building Envelope:

Figure 46. Building Materials in Standard Design and Energy Efficient Design Case

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5.2.5. Door & Windows Schedule:

Table 5. Door Schedule

Table 6. Window Schedule

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1

2

8

3

9

4

6

5

7

DN

W

A

W

W

W

W

W

D5

Food Preparation Area

D4

W

Dark Room

Lab

Microbiology

W

Drying Room

PROJECT NAME:

D4

ECG Room

Scan Room

B

Male Nurse Station

House Keeping Room

X-Ray

D2

D2

Corridor

Female Ward

Blood Collection

D3

Male Ward

D3

C

D4

Consultant 04

N

W D2

D4

Laboratory

D2

HOSPITAL BUILDING

Physiotherapy Room

D4 D4

D4

Female Nurse Station

Store Room DN

Jawaharlal Nehru Architecture and Fine Arts University

Female Staff Room

D2

D3

D3

A

Ladies Common Toilet

D4

B

W

Male Staff Room

Dining Area

W

W

W

D5

Gents Common Toilet

Pharmacy

W

C

W

TITLE: Consultant 05

Accounts Section

Cash Counter

Consultant 06

MD Room

W

W

GROUND FLOOR PLAN D4

Consultant Waiting Area

D

D4

D4

D4

D

D1 Reception / Waiting Area

Emergency Room D1

Ladies Toilet D5

Consultant 01

E

W

Consultant 02

W

Consultant 03

D

Gents Changing Room

E

W

DN

DN

1

2

8

1 : 100

SCALE

D5

NAME: W

ENTRANCE

01

W

Gents Toilet

D

W DN

Ladies Changing Room

SHEET NO.

P. PRAVEEN

ROLL.NO: 18011BB038 SEM:

VIII

BRANCH:

F.S.P

REMARKS:

9

3

4

5

6

7

SIGNATURE:

1

2

W

A W

Bedroom 08

W

D4

Bedroom 07 D5

3

9

W

4

W

Male Staff Change Room

D1

Bedroom 09

W

8

W

W

W

Female Staff Change Room

D1

Cath Lab

D1

6

5

Operation Theatre 01 D1

7

W

W

Housekeeping Room

Sub Sterile Service Room

A

Jawaharlal Nehru Architecture and Fine Arts University

D5

Operation Theatre 02 D1

PROJECT NAME:

Bedroom 06 D4

W

B

B Bedroom 10

D5

Bedroom 05

Doctor's Room

Male Staff Room

Bedroom 11

W

Corridor

D1

D1

HOSPITAL BUILDING

D5

D5

N

Female Staff Room

D1

D1

Isolation Room

CH105.100 CH110.12 24/72

W

Bedroom 12

24/72

W

C

Bedroom 04

C

Bedroom 13

W

Bedroom 03

D1 Urology Scan Room Conference Room D1

D W

Bedroom 14

W

D1

D

SHEET NO.

D5 ENT Scan Room

ENT Consultant

Visitor's Room

Bedroom 15

FIRST FLOOR PLAN

W

D1

Bedroom 02 D4

TITLE:

W

Urology Consultant

02

Intestine Scan Room

Intestine Medicare

D5

D5

1 : 100

SCALE

W

Bedroom 01 D1

D1

D1

NAME:

D1

E

E

P. PRAVEEN

ROLL.NO: 18011BB038 SEM:

VIII

BRANCH:

F.S.P

REMARKS:

1

2

8

9

3

4

5

6

7

SIGNATURE:

Jawaharlal Nehru Architecture and Fine Arts University

PROJECT NAME:

HOSPITAL BUILDING

N EAST

SOUTH TITLE:

BUILDING ELEVATIONS SHEET NO. 03 1 : 100

SCALE NAME:

P. PRAVEEN

ROLL.NO: 18011BB038 SEM:

VIII

BRANCH:

F.S.P

REMARKS:

WEST

NORTH

SIGNATURE:

1

2

8

9

3

4

5

6

7

DN

A

A

Jawaharlal Nehru Architecture and Fine Arts University

PROJECT NAME: B

B

HOSPITAL BUILDING DN

N UP

C

C

TITLE:

GROUND FLOOR PEDESTAL AND FALSE FLOOR LAYOUT D

D

SHEET NO. 05 SCALE NAME:

E

E DN

DN

2

8

P. PRAVEEN

ROLL.NO: 18011BB038 SEM:

VIII

BRANCH:

F.S.P

REMARKS:

DN

1

1 : 100

9

3

4

5

6

7

SIGNATURE:

1

2

8

9

3

4

5

6

7

A

A

Jawaharlal Nehru Architecture and Fine Arts University

PROJECT NAME:

B

B

HOSPITAL BUILDING

DN

N CH105.100 CH110.12

DN

C

C

TITLE:

FIRST FLOOR PEDESTAL AND FALSE FLOOR LAYOUT D

D

SHEET NO. 06 SCALE NAME:

E

E

1 : 100 P. PRAVEEN

ROLL.NO: 18011BB038 SEM:

VIII

BRANCH:

F.S.P

REMARKS:

1

2

8

9

3

4

5

6

7

SIGNATURE:

5.2.6. Cooling Loads: Load Calculation Inputs: Total air conditioning space (G+1): 3580 sqm (38,500 sqft) The critical inputs in the design of heat loads are: ❖ Design conditions: Location, Latitude, and Elevation. ❖ Outdoor temperature and relative humidity. ❖ Orientation. ❖ Internal conditions, indoor temperature and relative humidity are maintained as per the ASHRAE/ISHRAE norms. ❖ Building enclosure, insulation levels of walls, ceilings, and floors. ● Window specification ● Thermal conductivity ● Solar Heat Gain Coefficient (SHGC) ● Infiltration and ventilation levels ● Interior and exterior shading ❖ Internal loads. ❖ Number of occupants. ❖ Lighting and power load.

5.2.7. Cooling Load Methodology: Load calculations have been performed using the e20 sheet. In these e20 sheets the values like sensible heat, latent heat, CFM per person, CFM per sqft, air change per hour, dry bulb temperature, wet bulb temperature, daily range, infiltration, etc., are fed as per the ASHRAE norms. After generating heat loads for every room in the hospital with the help of e20 sheets in different design cases, the generated heat loads are as follows: Thumb Rule: In the thumb rule design case, the calculated cooling load is 205 TR E-20 Calculation Method: The e-20 calculations were made in two cases: ● Standard Design Case: 133 TR ● Energy Efficient Design Case: 104 TR

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Figure 47. E-20 Calculation sheet of Standard Design Case for Emergency Room

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Figure 48. E-20 Calculation sheet of Energy-Efficient Design Case for Emergency Room

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Table 7. Heat Load Summary of Energy Efficient Design Case

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Table 8. Energy Efficient Design Case Considerations for Ground Floor

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Table 9. Energy Efficient Design Case Considerations for First Floor

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9

5

A

Jawaharlal Nehru Architecture and Fine Arts University

PROJECT NAME: B

HOSPITAL BUILDING

DN

N Female Ward

Male Ward

96 m²

96 m²

C

TITLE:

Ground Floor HVAC Spaces & Zones D

SHEET NO. 01

Emergency Room 138 m²

SCALE NAME: E DN

DN

1 : 100 P. PRAVEEN

ROLL.NO: 18011BB038 SEM:

VIII

BRANCH:

F.S.P

REMARKS: Zone-01

1

2

8

3

4

6

7

SIGNATURE:

9

5

Zone-02

A

Pharmacy

Male Staff Room

Female Staff Room

36 m²

37 m²

82 m²

Dining Area

Jawaharlal Nehru Architecture and Fine Arts University

43 m²

PROJECT NAME: Female Nurse Station

Male Nurse Station

19 m²

19 m²

B

HOSPITAL BUILDING

DN

Physiotherapy Room 42 m²

Scan Room

ECG Room

46 m²

23 m²

N

Corridor 241 m²

C

Cash Counter 16 m²

Accounts Section

MD Room

65 m²

25 m²

TITLE:

Ground Floor HVAC Spaces & Zones D

Consultant Waiting Area

SHEET NO.

45 m²

02

Reception / Waiting Area 150 m²

SCALE NAME: E

DN

DN

1 : 100 P. PRAVEEN

ROLL.NO: 18011BB038 SEM:

VIII

BRANCH:

F.S.P

REMARKS:

1

2

8

3

4

6

7

SIGNATURE:

9

5

A

Jawaharlal Nehru Architecture and Fine Arts University

PROJECT NAME: B

DN

Lab

Microbiology

12 m²

7 m²

Dark Room

Drying Room

2 m²

4 m²

Laboratory

X-Ray

21 m²

34 m²

HOSPITAL BUILDING

N

Blood Collection 3 m²

C

TITLE:

Zone-03

Ground Floor HVAC Spaces & Zones D

SHEET NO. 03 SCALE NAME:

E DN

DN

1 : 100 P. PRAVEEN

ROLL.NO: 18011BB038 SEM:

VIII

BRANCH:

F.S.P

REMARKS:

1

2

8

3

4

6

7

SIGNATURE:

9

Zone-04

5

A

Cath Lab

Operation Theatre 01

40 m²

38 m²

Sub Sterile Service Room 15 m²

Jawaharlal Nehru Architecture and Fine Arts University

Operation Theatre 02 38 m²

PROJECT NAME: HOSPITAL BUILDING B

Isolation Room

24/72

233 m²

CH105.100 CH110.12 24/72

N

C

TITLE:

Ground Floor HVAC Spaces & Zones

D

SHEET NO. 04 SCALE NAME:

1 : 100 P. PRAVEEN

ROLL.NO: 18011BB038 E

SEM:

VIII

BRANCH:

F.S.P

REMARKS:

1

2

8

3

4

6

7

SIGNATURE:

9

5

A

Male Staff Change Room 40 m²

Female Staff Change Room

Jawaharlal Nehru Architecture and Fine Arts University

38 m²

PROJECT NAME: HOSPITAL BUILDING B

N Male Staff Room

Female Staff Room

60 m²

43 m²

43 m² CH105.100 CH110.12 24/72

Doctor's Room

24/72

Corridor 303 m²

Urology Consultant

Urology Scan Room

45 m²

34 m²

-

C

TITLE:

Ground Floor HVAC Spaces & Zones

---

Conference Room 82 m²

D

SHEET NO. 05

Visitor's Room

ENT Scan Room

103 m²

34 m²

Intestine Scan Room 37 m²

SCALE

1 : 100

Intestine Medicare

NAME:

45 m² ENT Consultant

P. PRAVEEN

ROLL.NO: 18011BB038

46 m²

E

SEM:

VIII

BRANCH:

F.S.P

REMARKS: Zone-05

1

2

8

3

4

6

7

SIGNATURE:

9

5

A

Jawaharlal Nehru Architecture and Fine Arts University

PROJECT NAME: B

HOSPITAL BUILDING

DN

N

C

TITLE:

Ground Floor UFAD Diffuser Layout D

SHEET NO. 06 SCALE NAME:

E DN

DN

1 : 100 P. PRAVEEN

ROLL.NO: 18011BB038 SEM:

VIII

BRANCH:

F.S.P

REMARKS:

1

2

8

3

4

6

7

SIGNATURE:

9

5

A

Jawaharlal Nehru Architecture and Fine Arts University

PROJECT NAME: HOSPITAL BUILDING B

24/72

CH105.100 CH110.12 24/72

N

C

TITLE:

First Floor UFAD Diffuser Layout

D

SHEET NO. 07 SCALE NAME:

1 : 100 P. PRAVEEN

ROLL.NO: 18011BB038 E

SEM:

VIII

BRANCH:

F.S.P

REMARKS:

1

2

8

3

4

6

7

SIGNATURE:

Jawaharlal Nehru Architecture and Fine Arts University

PROJECT NAME:

HOSPITAL BUILDING

N SECTION: RAISED ACCESS FLOOR

SECTION: ACCOUNTS ROOM TITLE:

UFAD Sectional & 3D Views SHEET NO. 08 SCALE NAME:

NTS P. PRAVEEN

ROLL.NO: 18011BB038 SEM:

VIII

BRANCH:

F.S.P

REMARKS:

3D EXPLODED VIEWS OF EMERGENCY ROOM

SIGNATURE:

Figure 49. Tonnage in various design cases

5.2.8. AHU Sizing: The AHUs are required for the five zones in the hospital. The capacity of AHU is designed according to the requirement of CFM for each zone.

The AHU capacities of each zone are

Table 10. AHU capacities of each zone

Application of Underfloor Air Distribution in Hospital Building

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Figure 50. Typical HVAC Equipment Range

Figure 51. Typical HVAC Equipment Setup

Application of Underfloor Air Distribution in Hospital Building

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5.3. UFAD Configuration: ● System Configuration: Conditioned air is distributed to diffusers across the entire floor area through a single, undivided non-pressurized open-plan plenum of 300mm (12 in.) height. Variable air volume (VAV) fan pressurized dampers are used to vary the supply air volume from zone thermostats. The return air ceiling plenum is 300mm in height. ● Diffuser Type: Variable volume round swirl floor diffusers of 10” diameter. ● Raised Access Floor: 600x600mm calcium sulfate panels of 30mm thickness. ● Pedestals: Adjustable galvanized steel tube pedestals with a diameter of 25mm.

5.3.1. Material Specifications:

Table 11. Material Specifications

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5.3.2. Water-Cooled Chiller Sizing: The total cooling load required for the hospital is 105 TR. The capacity of the chiller should be oversized by 20% of the cooling capacity or can be multiplied by the cooling load by 1.2 times.

Therefore, 105 TR + 21 TR = 126 TR

105 TR * 1.2 = 126 TR

5.3.3. Cooling Tower Sizing: The cooling tower capacity is calculated by the amount of total water flow in GPM. The operating and water usage conditions are,

Application of Underfloor Air Distribution in Hospital Building

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Figure 52. Estimated Cooling Tower Water Usage

The size of the cooling tower is, Cooling Tower TR = Cooling tower flow in GPM * Cooling tower range / 24 180 * (95-85)/24 = 75 TR

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5.4. Computational Fluid Dynamics (CFD) Analysis: A 3D-CFD investigation of airflow, temperature distribution and thermal comfort in hospital air-conditioned with underfloor air distribution (UFAD) system is presented for different operating and geometric conditions.

Numerical simulations are implemented to understand the effects of supply air temperature, supply air velocity, space height and number of supply air diffusers on the performance of the air conditioning system and thermal comfort in the emergency room.

Figure 53. Emergency Room Model for UFAD CFD

Figure 54. UFAD Diffuser Flow and Swirl Angle Considerations

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5.4.1. Simulation Run Results: ● UFAD Diffusers Swirl Flow Movement:

Figures 55. Plan Views of Diffusers Swirl Flow Movement

Figures 56. 3D Views of Diffusers Swirl Flow Movement

Application of Underfloor Air Distribution in Hospital Building

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Figures 57. Sectional Views of Diffusers Swirl Flow Movement

● Surface Plots Results:

Figure 58. Plan View of Surface Temperature Plots

Figure 59. 3D View of Surface Temperature Plots

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● Counter Plots Results:

Figure 60. Temperature Contour Plot at 0.70m Height

Figure 61. Temperature Contour Plot at X-Plane

Figure 62. Relative Humidity Contour Plot at 0.70m Height

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● Airflow Lines Results:

Figure 63. Plan View of Airflow Lines

Figure 64. 3D View of Airflow Lines

Figure 65. Typical Airflow lines near patient

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● Occupant Thermal Comfort Index:

Figure 66. Thermal Comfort Index in Plan View

Figure 67. Thermal Comfort Index in 3D View

Figure 68. Thermal Predicted Mean Value (PMV)

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● Room Stratification Test Results:

Figure 69. Room Air Stratification

Figure 71. Room Air Stratification at Feet Level

Figure 70. Room Air Stratification at Plenum Level

Figure 72. Room Air Stratification at Sill Level

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Figure 73. Room Air Stratification at Body Level

Figure 74. Room Air Stratification at Head Level

Figure 75. Room Air Stratification at Ceiling Level

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5.4.2. UFAD Model Interior Views:

Figure 76. Reception / Waiting Area

Figure 77. Emergency Room

Figure 78. Underfloor Plenum Pedestals

Figure 79. VAV Fan Pressurized Diffuser

Figure 80. Accounts / Office Room

Figure 81. Doctor Consultation Room

Figure 82. Physiotherapy Room

Application of Underfloor Air Distribution in Hospital Building

Figure 83. Canteen

Page | 59

Figure 84. Pharmacy

Figure 86. Staff Room

Figure 88. Isolation Ward

Application of Underfloor Air Distribution in Hospital Building

Figure 85. Conference Room

Figure 87. Corridor

Figure 89. Operation Theater

Page | 60

5.4.3. Simulation Run Summary: The results showed that: ● The used numerical technique could accurately predict the airflow and temperature distribution in the high rise conditioned space, ● UFAD system is capable of creating smaller vertical variations of air temperature and a more comfortable environment and energy saving, ● The supply air velocity and temperature, number of diffusers and height of the space have a significant impact on thermal comfort, ● The optimum system performance and thermal comfort obtained at 18 °C supply air temperature, 0.8 m/s supply air velocity and proper numbers and distributions of supply diffusers, ● The percentage of energy saving due to the usage of UFAD system increases with increasing height. ● As a result, the room showed thermal stratification, thus improving thermal comfort.

5.5. Construction & Commissioning Phases As underfloor air distribution (UFAD) systems often represent a new approach for many contractors, it is important that members of the construction team recognize the differences from the conventional methods to which they are accustomed. In most projects, the implications of the raised floor system and the creation of an underfloor air supply plenum will represent the most significant change. This section presents a number of planning, coordination, and installation issues that should be considered from the beginning of the design phase, through construction, and into occupancy, including the commissioning process.

5.5.1. Construction Phase: The following discussion is based on information obtained from designers and installers who have previously worked on UFAD projects.

Prior to installation of the raised floor system, the slab must be cleaned and sealed to reduce dust and, if desired, to inhibit bacterial growth. When a well-planned construction sequence is employed, the finished raised floor surface is not installed until after most of the dirt generating construction work has been completed. Careful coordination of these activities can

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help reduce the number of times the slab will need to be cleaned before installation of the raised floor. Any dirt/dust or materials that enter the underfloor plenum prior to occupancy must be removed (e.g., by vacuum cleaner or wet cloth) and the floor cleaned one final time before the internal fit out is completed.

The following sequence is recommended, as it limits the disruption of having to work on the slab with pedestals in place, prior to the placement of the floor panels.

1. Thoroughly clean slab surface.

2. Apply any coating or sealant to the slab.

3. Mark the grid of raised floor pedestal locations on the slab surface, but do not install them. This requires careful preplanning and layout of the raised floor grid in relation to all specified underfloor services. By not installing the floor pedestals until after all major building services in the underfloor plenum have been installed on the clean slab surface, contractors can work faster and safer.

4. Install perimeter and other required fan terminal units, other HVAC components, and all required underfloor air distribution ductwork, except air highways and underfloor partitions.

5. Install underfloor wiring for power/voice/data. Cable runs should be terminated with a coil of extra lengths sufficient to reach all possible locations (floor boxes or partition connections) served by that run.

6. Install all required piping (e.g., hot water supply and return serving perimeter heating coils). Access may be provided along with perimeter columns.

7. Verify that all vertical surfaces that are to be located adjacent to the access floor cavity have been adequately sealed according to the floor plenum leakage specification (to be provided to all involved contractors). This includes all junctions of these surfaces with the building slab, penetrations of drywall and other vertical partitions, and any other boundaries with the building slab.

8. Install pedestals and solid raised floor panels.

9. Install air highways and any underfloor partitioning at desired locations. Pay close attention to the sealing of air highways since they are operated at higher pressures than the plenum. Floor panels forming the top surface of air highways should be sealed (taped) around all edges and marked as being permanent (not to be removed even temporarily). See further discussion of plenum sealing below.

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10. Determine floor diffuser and power/voice/data terminal locations. In open plan offices, this requires careful pre planning of the locations for partitions and workstation furniture. It also requires consideration of the locations of all major HVAC elements in the underfloor plenum, including fan terminal units, large ductwork, and air highways (if specified). Access to these underfloor components will need to be maintained. All locations are tied to the floor grid originally laid out in step 3 above. Diffusers and cable outlets can then be assigned as desired (e.g., one per workstation, etc.). Large HVAC components should not be located in areas where diffusers will be placed, since nearly all diffusers include baskets and catch basins that hang below the bottom surface of the floor panels into the underfloor plenum.

11. It is preferable to keep solid floor panels in place until diffusers are installed to maintain the raised floor as a safe working platform and to help preserve the cleanliness of the underfloor plenum. Diffusers may be more efficiently installed in precut panels at staging areas. If necessary, install pre cut floor panels (at locations determined in step.

12. When all dirt/dust-generating construction activity is completed, thoroughly clean the top surface of the raised floor plenum and, if needed, clean the underfloor slab surface at any locations that have accumulated dirt.

13. Install floor diffusers/panel assemblies and power/voice/data terminals.

14. Install carpet tiles according to manufacturer’s specifications, cutting access holes for all diffusers, grilles, and power/voice/data terminals.

During the construction stage, as-built drawings should be made available, indicating the exact location of services within the underfloor plenum for future access, maintenance and system upgrades.

Floor contractors generally provide access holes in the floor panels for diffusers, power/voice/data terminals, and other outlet boxes. Mechanical contractors should be responsible for all required ductwork (except perhaps air highways) and the installation of all floor diffusers, grilles, fan terminal units, and other mechanical equipment in the underfloor plenum.

In the large majority of raised floor system applications, carpet tiles are installed on top of the floor panels. In addition to providing the finished floor surface, the carpet tiles serve a second important purpose by providing a seal over the top of the raised floor installation. Due to the

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large surface area, leakage through the gaps between floor panels can be significant in pressurized plenum systems. Carpet tiles can reduce the amount of leakage by a factor of 2 or 3 in comparison to bare floor tiles. If bare floor panels without carpeting are used, some provision for sealing between floor panels must be provided or large leakage rates can be expected and must be accounted for in the operation of the UFAD system.

Care must be taken to avoid using an excessive amount of adhesive as it may make it difficult to remove carpet tiles to gain access to the floor panels during subsequent relocation, replacement, or service work. Adhesive accidentally seeping into the underfloor plenum may also damage cable-management components and negatively affect the quality of the supply air.

5.5.2. Commissioning Phase: Following the construction phase, a carefully conducted commissioning of a UFAD installation will go a long way toward ensuring that all building systems are properly applied, installed, and operated, despite the novelty of this technology to some members of the design and construction teams. Commissioning is a systematic process that begins in the design phase and extends through occupancy and the warranty period for the building and uses documentation and verification methods to make sure that the facility meets the design intent and the expectations of the owner and occupants.

The UFAD system commissioning should include an airway-leakage test and an airflow test.

Begin by testing each primary supply fan to check for minimum airflow with all diffusers closed or at the minimum stop. If uncontrolled leakage (leakage not coming through the diffusers and not what is expected through the floor) is too high, the leakage needs to be found and corrected, and the primary supply fan must be retested. The leakage test itself should be repeated every few years or after any remodeling that includes reconfiguring the UFAD system. An airflow/SP test determines that the system can provide adequate air to all diffusers. Typically, test one diffuser per zone and verify that the zone controllers are functioning properly (based upon the predefined sequence of operation). Balancing the diffusers is necessary only on ducted diffusers (often used along the perimeter).

Because of the important balance between room airflow and heat input to the space, proper and complete commissioning of a UFAD system will require operation and adjustment of the system under peak (or close to peak), as well as partial, cooling load conditions. During

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preliminary HVAC system commissioning prior to building occupancy, supply air quantities and temperatures can be established according to design estimates. Since standardized design tools based on fundamental research are not yet available, designers will need to proceed cautiously using an empirical approach where they rely on their previous experience with UFAD systems, the experiences of others, or other available information to guide their design decisions. Until the space is occupied and subject to typical cooling loads, however, it will be difficult to verify the proper system operation. Commissioning performed after occupancy (with more typical cooling loads present) will serve as the best approach to achieve the desired system operation.

5.6. Controls, Operation & Maintenance The control and optimization of temperatures in the occupied zone and the amount of thermal stratification (during cooling operation) is crucial to system design and sizing, energy-efficient operation, and comfort performance of UFAD. This section presents and discusses: 1. Recommended control strategies for effective system operation, 2. Incorporation of individual control to allow occupants to fine-tune their local environment, and 3. Operations and maintenance (O & M) issues differ from issues in conventional system operation.

5.6.1. Control Strategies in Pressurized Plenum: This section presents control strategies that have been developed and applied in underfloor air distribution (UFAD) installations. ● Supply Air Temperature (SAT): Since air is supplied directly into the occupied zone near floor level, minimum supply outlet temperatures should be maintained in the range of 61-65°F (16-18°C) to avoid overcooling nearby occupants. For TAC supply outlets located closer to the occupants and used to provide velocity cooling, even warmer minimum supply air temperatures may be advisable.

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● Constant Pressure (CAV): A common control method for interior zones maintains constant static pressure in the underfloor plenum to ensure constant volume air flow from each diffuser (similar model and setting). Plenum pressure is maintained by adjusting fan capacity at the air handler.

Occupants can make minor changes to local comfort conditions by manually adjusting a diffuser, but such adjustments are viewed as setup adjustments, not operating adjustments. As long as load variations in the zone due to diversity and other occupancy changes are small, and the net impact on plenum pressure by occupant diffuser adjustments is minimal, this strategy results in very nearly a constant-air volume (CAV) operation and can maintain acceptably comfortable space conditions. In this configuration, one strategy for controlling supply air temperature that has been applied successfully in practice is to use measured return air temperature as a means of maintaining stratification at the desired level.

In CAV spaces, constant supply air temperature with decreasing load causes the space temperature profile to shift toward cooler temperatures and become less stratified. In this case, the average occupied zone temperature tends to be a few degrees cooler than the peak load thermostat temperature. Thus, supply air temperature (SAT) reset is recommended. ● Variable Air Volume (VAV): Perimeter zones typically experience load changes that are greater in both magnitude and frequency than those encountered in interior zones. Automatic VAV control is the preferred strategy in perimeter and special zones (e.g., conference rooms) with these rapidly changing loads. Under VAV control, as load changes, room airflow and diffuser flow rate will change.

Recent tests indicate that VAV operation with constant supply temperature results in a characteristic room air stratification temperature profile that is relatively consistent for moderate changes in load. Most designers are now more frequently considering VAV control in the interior zone as an approach to minimize over-airing (overcooling) and to avoid starving the perimeter zone through SAT reset. ● Controlling Stratification: The objective of controlled stratification is to minimize energy use (reduce room airflow) while maintaining comfort (acceptable temperatures and stratification in the occupied zone).

Overall room air stratification is primarily driven by the balance of room airflow rate in relation to the room cooling load.

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On the other hand, if too much air is delivered to the space, stratification will be reduced, approaching a well-mixed room at the upper limit. Increasing or decreasing the supply air temperature (for constant load and room airflow) does not change the fundamental shape of the stratification profile but simply moves it to higher or lower temperatures.

These principles are demonstrated in the example stratification control sequence shown in Figure. Figure 90 shows three different vertical temperature profiles [temperature (T) vs. height (H)]. The profiles are not based on measured data but rather are shown for illustration purposes only.

Figure 90. Example sequence for controlling thermal stratification.

The sequence of moving from Profile #1 to Profile #3 is intended to demonstrate how controlling stratification in UFAD systems requires different considerations than for traditional overhead systems. In this example, stratification is controlled by adjusting airflow and SAT to achieve comfort conditions in the occupied zone for various thermostat settings.

The cooling load is assumed to be constant and at its peak value in all three cases.

Profile #1 shows a modest amount of stratification (temperature gradient) characterized by supplying too much air to the room. As indicated, the temperature at the thermostat height (shown to be 60 in. [1.5 m]) is TSTAT1, and the average temperature of the occupied zone (from 4 to 67 in. [0.1 to 1.7 m]) is Toz1, avg.

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Profile #2 represents an alternative design load condition where airflow is reduced. To meet the same thermostat control point (TSTAT1=TSTAT2) with reduced airflow, the SAT also must be decreased. However, due to increased stratification, the average temperature of the occupied zone (Toz2, avg), which along with the gradient is representative of overall comfort conditions, has been reduced. If the SAT is increased so that the occupied zone temperature is equivalent (Toz3, avg = Toz1, avg) to that of Profile #1, Profile #3 is produced. This simple example shows how both supply volume and SAT can be manipulated to create various occupied zone comfort conditions for given thermostat settings. The process of moving from Profile #1 to Profile #3 also demonstrates an approach that could be followed during commissioning to achieve the desired amount of stratification under peak load conditions.

ASHRAE Standard 55-92 [ASHRAE 1992] specifies that the amount of stratification in the occupied zone (temperature difference between head and ankle heights for a standing person) be limited to 5°F (3°C). One of the challenges of maintaining comfort in a stratified environment is that the thermostat temperature can no longer be assumed to represent the average temperature in the occupied zone. This is particularly true for thermostats located at a height of 5 ft (1.5 m) near the top of the occupied zone and therefore measuring close to the maximum occupied zone temperature. Because of this, it may be necessary to consider increasing the thermostat setpoint by up to 1-2°F [0.5-1°C] above the desired occupied zone setting under peak load conditions. The recently changed building code requiring thermostats to be installed at a lower 4 ft (1.2 m) height may help alleviate the need to adjust the setpoint as it will be measuring closer to an average temperature in the occupied zone. In any case, a balance between the amount of stratification and average, or representative, occupied zone temperature must be achieved within the limitations of room airflow and SAT available from the system. ● Humidity Control: One way to achieve the required higher supply air temperatures while still maintaining humidity control uses return-air face and bypass. Cooling coil temperatures are typically in the range of 50-55°F (10-13°C) for dehumidification purposes. Only the incoming outside air and a portion of the return air is dehumidified (minimum amount needed for humidity control). The remaining return air is bypassed around the coil, if done at the air handler, and mixed with the cool primary air to produce supply air of the proper temperature and humidity before being delivered directly into the underfloor plenum. The face and bypass dampers are

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controlled to achieve the desired supply air temperature as load changes. To save energy, the coil temperature can be varied to control humidity so a greater coil leaving temperature can be used when entering humidity conditions are low. If desired, this configuration also allows a range of coil temperatures to be utilized, including low-temperature air systems with or without ice storage.

5.6.2. Control Strategies in Zero-Pressure Plenums: Although active diffusers may be installed in both zero-pressure and pressurized plenums, this section will focus on control issues associated with zero-pressure plenums with diffusers that are more likely to be adjusted by individual occupants.

Control strategies for the building's central mechanical system should be well coordinated with the local supply outlets. Supply volume control of the central air handler requires a different approach with zero-pressure underfloor air distribution systems. Due to the extremely small or nonexistent pressure differentials between the supply plenum and the space, traditional pressure-sensing methods do not provide accurate measurements for control purposes. A CAV-VT approach has been successfully used, but the chance of over-airing or resetting SAT too high under part-load conditions must be carefully guarded.

An ingenious VAV control strategy proposed by Shute [1992] addresses the need to balance the airflow delivered by the central AHU into the plenum with the airflow leaving the plenum. The approach uses a temperature sensor in a vertical induction shaft directly connecting the return air at ceiling level to the underfloor plenum. Under normal operating conditions with this design, the active floor supply units will be delivering slightly more air to the space than is provided by the central system. So in fact, the plenum will be operated at a slight negative pressure. In this case, the temperature sensor will measure normal room return temperatures as the air is drawn down the induction shaft to mix with incoming primary air.

If, however, the temperature in the induction shaft decreases rapidly, it indicates that the demand for air supply through the floor supply units has been reduced (i.e., fan units have been turned down or off), resulting in the overpressurization of the underfloor plenum. The central air handler can then be throttled down until the reversal in flow direction through the induction shaft is eliminated. A minimum setpoint at the air handler can be used to ensure that sufficient airflow is always supplied to the space.

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5.6.3. Operation & Maintenance: As with any new building system, building operators should be properly trained to allow the operation and control of the UFAD or TAC system to be optimized. Experience with early projects has demonstrated that UFAD and TAC systems that are operated using traditional control strategies based on mixing air distribution system performance are likely to have deficiencies in energy and operating costs as well as comfort performance.

5.6.4. Designing for Maintenance: Depending on the type of underfloor air distribution technology selected and the loads served, there may be a fair amount of equipment located under the raised floor (i.e. fan-powered boxes, volume control dampers, etc.) The most important design issue here is making sure there is adequate room and access to perform routine maintenance and repair. Things to consider include: ● Equipment access panels are not blocked. ● Enough room is available for equipment removal and installation. ● Equipment is located so that filters can be replaced easily. ● Furniture does not impede access to the equipment.

Among the O & M issues that may differ from those encountered with conventional system design are the following.

5.6.5. Cleaning Considerations in Underfloor Plenums: A common concern among occupants of buildings with UFAD systems using floor grilles is that dirt and spillage will more easily enter the underfloor plenum where it will mix with the air supply stream and be distributed throughout the occupied space. Experience has shown that if the plenum area is thoroughly cleaned at the end of construction, the amount of dust buildup on the slab is not excessive and can be handled through cleaning scheduled as part of normal plenum reconfiguration work. The required frequency of this type of cleaning is estimated to be two to three years depending on the observed rate of buildup. Dirt and particulates that do fall into floor diffusers will be collected by the catch basins beneath the diffusers. These basins should be cleaned as part of the regular maintenance schedule, depending on rate of build-up.

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Two important considerations are that ● Except near the plenum inlets, air speeds within the underfloor plenum are so low that they do not entertain any dirt or other contaminants from the plenum surfaces into the supply air, and ● If a spill or other accidental contamination, such as fire, arises that does require cleaning, the accessibility of the underfloor plenum makes this process far simpler and more effective than in the case of overhead ductwork.

5.6.6. Reconfiguring Building Services: The improved flexibility of raised floor systems provides significant cost savings associated with the reconfiguration of building services. One consideration during the relocation of furniture is that floor diffusers will often need to be moved (even though it is easy to do so) to accommodate the new positions of the furniture. This may actually add costs compared to overhead HVAC systems, which will typically not be reconfigured (at a potential cost of reduced system performance). Building operations staff will also need to maintain an adequate surplus stock of floor panels and carpet tiles to handle the required reconfigurations in response to the churn rate of the building occupants.

5.6.7. Acoustic Performance: Due to the elimination or minimal use of ductwork in underfloor plenums, the noise generated from the operation of a UFAD system can be substantially less than that from a conventional ducted overhead system. This reduction in commonly found levels of background “HVAC” noise may create a situation where active sound masking or other acoustic design measures may be required.

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5.7. Life Cycle Cost Analysis (LCC):

Table 12. LCC Comparison of OHAD & UFAD

Life-cycle cost components include those building elements whose costs are affected over the lifetime of the building and represent the primary means by which building owners can expect to receive a greater return on their initial investment.

5.7.1. Installation Costs: Many owners and developers have found that raised floor systems with UFAD significantly reduce costs associated with space reconfiguration. Buildings using UFAD systems have certain cost components that make them more expensive than traditional systems and compensating ones that lower the overall price premium that currently exists for this application. A few of these cost components are: ● The raised floor system is the component with the single largest cost increase, which should be cost justified based on the benefits to the entire service delivery system (HVAC, power, voice and data) and not against the UFAD alone. ● Local building and fire inspectors may require sprinkler protection if plenum depth exceeds 18 inches and often require smoke detectors within the plenum. ● Generally, HVAC costs for central cooling and heating equipment and ductwork mains are no different for UFAD systems.

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● Diffuser costs are dependent on the type(s) chosen for the majority of air delivered. ● If a relatively open underfloor plenum can be used, significant ductwork savings can be realized compared to the typical overhead air distribution system. ● Control costs should be similar to traditional systems when basic zoning is unchanged. ● Raised floor systems have the potential to reduce slab-to-slab heights by as much as 6 to 12 inches per floor. This is particularly beneficial in mid-rise and high-rise markets with zoning code height limitations. ● Testing and balancing savings can be realized from CAV pressurized plenum designs, which are essentially self-balancing.

5.7.2. Energy Usage: UFAD systems have the potential to save energy in comparison to traditional designs. The bulk of these savings come from reduced fan energy associated with lower static pressures and overall CFM reductions created by the stratification layer partial displacement ventilation effect. Documented energy cost savings remain difficult to predict because to date there is no energy simulation software that accurately models UFAD system performance.

5.7.3. O & M Considerations: Operations and maintenance costs are primarily replacement costs for equipment and labor expenses associated with maintaining the HVAC system and responding to occupant complaints. While many engineers believe that UFAD may prove to be more costly to service, research suggests that the frequency of occupant complaints will be reduced when they are given some individual control of their local environment.

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5.8. UFAD & Sustainable Green Buildings: UFAD systems can contribute towards achieving credits towards a green certification: ● Optimize energy performance ● Material reuse ● Recycling of access flooring ● Re-use of access flooring components ● Ventilation increases ● Thermal comfort ● Controllability of systems ● Reduced building height and construction materials Many projects now require green building certification. Points can potentially be gained with UFAD systems in several areas: 1. Mechanical equipment downsizing 2. Part load efficiencies 3. Recyclability of office components 4. While LEED no longer gives ventilation credit for UFAD systems (because ASHRAE 62 no longer gives ventilation credit for UFAD), there is a proposed change in progress that will allow reduced outdoor air with short throw UFAD outlets 5. Occupant comfort control.

The table below shows the LEED credits that could be achieved with UFAD systems.

Table 13. LEED credits that could be achieved with UFAD systems Application of Underfloor Air Distribution in Hospital Building

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5.8.1. Optimize Energy Performance: The intent of this credit is to achieve increasing levels of energy performance above the prerequisite standard to reduce environmental impacts associated with excessive energy use.

Credits are based on a percentage of reduction and range from 10.5% reduction (1 Point) to 42% reduction (10 Points) for new buildings.

The requirement for optimizing energy performance credit is to reduce the design energy cost compared to the energy cost budget for systems regulated by ASHRAE™/IESNA Standard 90.1-2004. Per LEED, regulated energy systems include HVAC, service hot water and interior lighting.

All LEED projects registering after June 26, 2007 are required to achieve at least two (2) Optimize Energy Performance points. One way to achieve energy optimization credit is with a UFAD system. A UFAD system may have higher HVAC equipment efficiency as access floor air systems use warmer supply air (63 to 68°F) than conventional systems that use 55°F supply air. Raising the discharge temperature of many system types reduces energy consumption.

UFAD systems can move a larger volume of air with overall lower pressure drops. The UFAD plenum needs less than 0.1” WG of water pressure or less for proper diffuser performance. This results in less fan horsepower needed for UFAD systems, and in turn, resulting in lower energy usage.

The energy savings of a UFAD system should be considered as part of the system to receive an Optimize Energy Performance credit. ECM motors are another option that should be considered with fan powered units. The ECM motor has efficiencies of up to 70% across its entire operating range (300-1200 rpm) and 80% over 400 rpm.

5.8.2. Building Reuse: If the project is a renovation, Credit 1.1, 1.2, or 1.3, Building Reuse, may be applicable.

Credit 1.1 is for maintaining at least 75%, based on the surface area, of the existing building structure and envelope. Credit 1.2 is for maintaining an additional 20%. Credit 1.3 is for maintaining 50% of existing interior non-structural elements such as interior walls, doors, floor coverings and ceiling systems. Each credit qualifies for one point; meeting the criteria for all three credits yields a maximum of three points for the Material & Resources section.

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Utilizing access floor systems can update a building for meeting current technology needs without demolishing the current building structure. In situations where the architect wants to leave an ornamental ceiling open, access floor air distribution may be the perfect solution.

5.8.3. Controllability of Systems: Credit 6, Controllability of Systems, has two parts: 6.1 Lighting and 6.2 Thermal Comfort.

The intent of Credit 6.2 is to provide individual comfort controls for 50% of the building occupants to enable adjustments to suit individual task needs and preferences.

The credit states that, “Individual adjustments may involve individual thermostat controls, local diffusers at floor as potential strategies to achieve this credit”.

5.8.4. Sustainable strategy with EDGE tool:

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Figure 91. Savings in energy usage

Figure 92. Savings in water usage

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Figure 93. Savings in material usage

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6.0. Conclusions ● The intention of this work is to offer solutions provided by studying the thermal comfort and contaminant removal effectiveness of a room. This type of information will help HVAC practitioners, and ultimately architects, find the best space distribution early in the design phase. The thermal environment of the UFAD system was investigated and the results were compared with the ASHRAE standards for thermal comfort. The results obtained from the CFD analysis gave details of the flow pattern and the flow characteristics of the models that have been analyzed. ● In the study of the 3D emergency room setting, it can be concluded that the flow characteristics and the thermal comfort factors are in the acceptable ranges of the ASHRAE standards. ● From the thermal comfort analysis, it has been observed that the contaminant removal effectiveness of the system is reasonably good and also the PMV is calculated to be -0.8 which is in the acceptable range on the thermal sensation scale. ● From the study of the UFAD system in a room, it can be observed that the flow is well mixed and distributed uniformly due to the swirl diffusers. ● From life cycle cost analysis comparison, overhead air distribution incurs less capital expense than underfloor air distribution. The overhead air distribution system has higher operating and maintenance costs than the underfloor air distribution system. ● With the UFAD system, there is a slightly more initial cost but the running cost is low and has a return on investment over the years. Thus, reducing building life cycle costs in the longer run.

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7.0. References (1) Bauman, F. 2003. Underfloor Air Distribution (UFAD) Design Guide. American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc. Atlanta, GA. Retrieved November 15, 2021 from, https://www.academia.edu/35838362/Underfloor_Air_Distribution_UFAD_Design_G uide (2) Underfloor Air Technology. Retrieved November 22, 2021 from, https://cbe.berkeley.edu/underfloorair/benefits.htm (3) Design Guide to Underfloor Air Distribution - Carrier. Retrieved November 26, 2021 from, https://www.shareddocs.com/hvac/docs/1001/Public/06/DS_UFAD.pdf (4) HVAC Overview of Underfloor Air Distribution (UFAD). Retrieved November 26, 2021 from, https://www.cedengineering.com/userfiles/HVAC%20Overview%20of%20the%20Un derfloor%20Air%20Distribution%20R1.pdf (5) Underfloor Air Distribution (UFAD) Solutions. Retrieved December 15, 2021 from, https://airfixture.com/ (6) Complete Guide to Underfloor Air Distribution. Retrieved January 20, 2022 from, (7) Tate 2007, Tate Access Floors: Design Guide. Retrieved January 24, 2022 from, https://www.tateinc.com/ (8) Designing Underfloor Ventilation in Hospitals. Retrieved February 13, 2022 from, http://www.marsdenwagner.com/designing-underfloor-ventilation-hospitals/ (9) Underfloor Air Distribution. Retrieved February 15, 2022 from, https://en.wikipedia.org/wiki/Underfloor_air_distribution#Air_leakage_in_UFAD_ple nums

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8.0. Annotated Bibliography [1] Addison, M., Nall, D. 2001. Cooling via underfloor air distribution: Current design issues and analysis options. From: Cooling Frontiers: The Advanced Edge of Cooling Research and Applications in the Built Environment. College of Architecture and Environmental Design, Arizona State University.

This paper provides a brief description of the significant features, potential advantages, and design issues associated with underfloor air distribution. The current and emerging whole building energy analysis and HVAC design simulation tools were described.

[2] Bauman, F., Webster, T. 2001. Outlook for Underfloor Air Distribution. ASHRAE J., June, pp.18-25.

This paper offers a system description, discusses the benefits of underfloor technology, and lists and discusses the "technology needs" or the current barriers to its widespread adoption (from UFAD Design Guide by Bauman).

[3] Daly, A. 2002. Underfloor air distribution: Lessons learned. ASHRAE J., Vol. 44, No. 5, May, pp. 21-24.

This paper presents three strategies for capturing as many benefits of underfloor air distribution as possible while keeping the initial cost to a minimum. They are: 1) minimize the ductwork in the plenum, 2) prevent plenum leakage, and 3) don't oversize airflows.

[4] Faulkner, D., Fisk, W.J., Sullivan, D.P. 1993. Indoor airflow and pollutant removal in a room with desktop ventilation. ASHRAE Trans., Vol. 99, Pt. 2.

The authors investigated the indoor airflow patterns and tobacco smoke removal efficiency of a desktop task ventilation system in a furnished experimental facility. The task ventilation system permits occupant control of the temperature, flow rate, and direction of air supplied through two desk-mounted supply nozzles.

[5] Han, H., Chung, K.-S., Jang, K.-J. 1999. Thermal and ventilation characteristics in a room with an underfloor air-conditioning system. Proc. Indoor Air '99, Edinburgh, Scotland.

This paper outlines the results of testing in a conference room with underfloor air-conditioning, including measurements of horizontal and vertical room air temperature

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distributions, CO2 concentrations and infra-red imaging of temperature distributions over a person standing on a floor-based supply outlet.

[6] Kim, I.G., Homma, H. 1992. Possibility for increasing ventilation efficiency with upward ventilation. ASHRAE Technical Data Bulletin, Vol. 8, No. 2.

The results of experiments comparing upward and downward ventilation systems in an office-like test space with human occupants indicate changes in room CO2 content are less affected by upward than by downward ventilation. This paper concludes that ventilation rates for removing occupant produced contaminants in the breathing zone can be low, providing supply air temperatures are less than room air temperatures (from UFAD Design Guide by Bauman).

[7] McCarry, B.T. 1995. Underfloor air distribution systems: benefits and when to use the system in building design. ASHRAE Trans., 1995, Vol. 101, Pt.2.

This paper addresses the optimum context and application for underfloor air distribution systems. Illustrated with reference to three buildings in Vancouver, Canada, the discussion addresses the design, mechanical systems issues, potential benefits and where the use of an underfloor air system is, or is not, appropriate (from UFAD Design Guide by Bauman).

[8] Webster, T., Bauman, F., Reese, J. 2002-a. Underfloor air distribution: Thermal stratification. ASHRAE J., Vol. 44, No. 5, May, pp. 28-36.

This article describes the idea of stratification, whose control and optimization is crucial for the system design of underfloor systems. This article focuses on the practical implications of room air stratification testing results for the control and operation of constant air volume and variable air volume UFAD systems (from UFAD Design Guide by Bauman).

[9[ Webster, T., Bauman, F., Reese, J., Shi, M. 2002-b. Thermal stratification performance of underfloor air distribution (UFAD) systems. Proc. Indoor Air 2002, Monterey, CA, 30 June - 5 July 2002.

This paper presents tests to “determine the impact of room airflow and supply air temperature (SAT) on the thermal stratification in interior spaces, and the effect of blinds in perimeter spaces for UFAD systems.” Results are outlined and discussed (from UFAD Design Guide by Bauman).

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