Design Project & Analysis Aim: Modular residential units located in the East Oxford area. 9 units of 3 bed capacity (satisfied on 00 and 01 floor) with work unit on 02 floor. For the purpose of this exercise only the 00 floor level is modelled, giving indication to the performance of the building as a whole.
s ighting Analysi L y d tu S e as C Model. Left: ign Sketch Up es D e iv at rm o Below: F
The design project prior to this report involved an analysis; a lighting / heating study of a terraced building in the East Oxford area, to further inform the design. The positive features of the case study were copied onto the new residential units. These desirable attributes were as follows:
The area of living space The window design (sizes, location and orientation) The orientation of the property as a whole.
Right: IES Mo
By using IES software we can decide whether these choices are beneficial to the buildingâ€™s performance / energy efficiency and what changes, if any, are needed to improve the design.
Construction / Characteristics: Build utilises local materials: Straw bale construction: prefabricated Modcell timber straw bale panels & wooden floor / roofing. The external walls are rendered with decorative timber slats on upper levels. The foundations / structural structural floor slab are both in-situ concrete. The IES software did not supply the correct materials to simulate the straw bale accurately. So, the model used a material of structural integrity and other wall materials (plaster and boarding) were kept accurate. The wall composition was as follows: Material Thickness Conductivity Density (m) W/ (m K) kg/m3
Specific Heat Capacity J/(kg K)
EXTERNAL RENDERING CHIPBOARD CEMENT FIBRE SLAB SHREDDED WOOD WITH... PINE (20% MOIST)
Chipboard layer & internal pine cladding was included to simulate the Modcell panels best, being composed of a blend of both dense insulation/structural straw bales and chipboard frame:
Right: Modcell panel & Typical Opening. Detail. Note wooden framework & render (grey). Project & simulation includes utilisation of chipboard framework.
Windows â€“ on three of the facades only - are low-e double glazed units. The control model was made without external shutters (to cater to the varying thermal comfort demands of itâ€™s users) intended to be later designed in if overheating occurs. The fourth faĂ§ade, without windows, has an external staircase connecting the building with a 3 storey green (sedum/moss) wall. This has a concrete frame with additional timber inset panel details. For the purpose of this exercise, this has been omitted from the 3D model as it is not in direct contact with the structure and internal spaces.
The Report: What Variables Are Being Tested? To determine the effects of design decisions (as above stated) upon the projected energy use of the building (heating, lighting) and upon thermal comfort (summertime overheating) the following will be investigated:
Orientation of terraced case study. Initial orientation to suit the direction of the terraced case study house = 48.8 degrees. Rotation by 90 degrees in each direction, to find optimum an gle for solar utilisation.
Thermal Mass. Reducing wall thickness.
Shuttered windows on windows. The affect of utilising external glazing on glazing to reduce summer overheating.
Model One. This model is used as a constant to monitor the affects of changes employed in the later simulations to the building’s performance.
Buildng Template Specifications: The Model Variables / Settings as seen in the Building Template Manager.
THERMAL CONDITIONS. Bespoke Annual Heating Profile. Composed of weekly profiles specified by season: Winter heating weekly profile: utilised from October 1 – May 1. Summer heating weekly profile: utilised from May 2 – September 30. Bespoke Weekly Heating profiles: Composed of daily profiles specified by season: Summer: Heating system continually off. Winter: Heating system on in accordance to weekly occupancy hours:
5.00am – 7.00am 4.00pm – 6.00pm
Simulation heating set point: 19 degrees celsius, an acceptable comfort temperature. Setting this higher would increase heating costs and energy consumption unnecessarily. No cooling system or humidity control was employed within the building due to energy use restrictions and temperate UK climate.
Right: Axonometric View, Model 1.
INTERNAL GAINS. Type
Maximum Maximum Occupancy Max Radiant Sensible Latent G... Power Fraction W/m2 W/m2
Flourescent Lighting Miscellaneous. People.
6.000 10.000 90.000 W/person
Biomass Biomass -
- 0.000 60.000 W/person
- - 12.000 m2/person
6.00 0.45 10.00 0.50 - -
All internal gain factors only come into action during the buildingâ€™s programmed occupancy hours. As found in the Apache Profiles Database, the occupancy profiles were set as follows: Bespoke Annual Occupancy Profile: Composed of weekly profiles based on school holiday period (and resultant likely patterns in occupation of a family home). Term Occupancy: Jan 16 - July 15 Holiday Occupancy: July 16 - August 15 Term Occupancy: August 16 - December 30 Holiday Occupancy: December 31 - Jan 15 Bespoke Weekly Occupancy Profile: Term Occupancy: Week composed of Daily Term Occupancy Profile from Monday - Friday and Daily Holiday Occupancy Profiles from Saturday - Sunday.
Holiday Occupancy: Week composed entirely of Daily Holiday Occupancy Profiles.
Early Site Plan Drawing. (Bottom) Orientation angle, taken from case study terraced housing translated into IES model. (Top)
CONSTRUCTION Opaque Elements: Roof Ceiling
Flat Roof (2002 regs) Type 5 Insulated Ceiling.
TO SPECIFICATION OUTLINED IN INTRODUCTION
Internal Partition Ground Floor Door
Type 2 Plaster / Airgap / Plaster Type 2 Insulated Solid Floor Wooden Door.
Glazed Elements: External Glazing
Low-e double glazing (6mm+6mm) (2002 regs)
GLAZING COMPLIANCE WITH PART L REGULATIONS: The glazing setting used in this model, is set as a standard construction in the IES database. It is essential for a building to achieve a minimal heat load to retain heat through the glazing. Low-e glazing, as specified in image below, are compliant to the needs specified in the recent Part L Building Regulations.
Facade Orientation And The Rendered Model 1. W.
Model 1. Higher solar gains notable in the kitchen. (dry resultant temperature / year)
Model 3. Lower solar gains notable in the kitchen. (dry resultant temperature / year) TEMPERATURE RANGE ANALYSIS: IES allows the user to analyse the simulation data in temperature ranges. The Model 1 data was analysed over the course of a year, and the hours of a recorded temperature 25 or over in the individual rooms were recorded. The building was then rotated and the ranges were recorded, to give comparison to which orientation would be best to reduce summer overheating. Hours in the year: Below individual hours are of a fraction of 8760.
MODEL 1 CONSTANT
KITCHEN LIVING STUDIO
4577 4560 4363
4403 4276 4395
4196 4311 4309
4397 4585 4232
CONCLUSION Results show that orientation / Model 3 is at the optimum angle to best reduce summer overheating. It however must be noted that that these totals are still considerably high. Further reduction of these excessive solar gains needs to be exercised. IT MUST BE NOTED THAT THIS MODEL DOES NOT UTILISE ANY VENTILLATION (IN MACROFLOW SETTINGS) THROUGHOUT THE YEAR ASSESSED. THIS WOULD CONSIDERABLY REDUCE EXCESSIVE HEAT RETENTION IN THE SUMMER MONTHS.
Model 3. Plan. Most Sucessful Orientation. Plans Altered according to IES investigation. (Top)
d r Be aste M 01 d Be 02 d Be . W
Plans. Altered orientation according to IES investigation. Simulated 00 Floor and upper 01 floor of actual building. (Top) Annual Heating Loads compared to External Dry Bulb Temperature, showing building is heated in coolest months. (Right) Rendered plan view of model 3, as optimum orientation to reduce summer overheating. (Below)
ing v i L
Comparing Data Generated In The IES Report. MODEL 3. Net Energy Consumption (MWh) Carbon Emissions (kgCO2)
THE LACK OF VENTILLATION, AND ITâ€™S IMPORTANCE TO PERCIEVED COMFORT OF INHABITANTS IS EXPRESSED BY THE RECORDED RELATIVE HUMIDITY AND MIN / MAX TEMPERATURES IN MODEL 3 (THE MOST SUCCESSFUL MODEL REDUCING SUMMER OVERHEATING). COMFORT DATA (WHEN OCCUPIED): Temp. Room Name Max Min
Rel. Humidity Max Min
LIVING STUDIO KITCHEN
100.0 100.0 100.0
43.1 44.9 44.0
15.2 15.2 14.6
70.4 69.9 68.2
It is therefore clear that natural ventillation is needed within the building unit to reduce humidity and temperature and thus improve the comfort of the inhabitants. The minimum temperatures, dipping below the comfort temperature (for the purpose of this modelling exercise set to be 19 degrees celsius, as seen in the building template manager) to as low as 14.6 degrees celsius shows further insulation is needed, and a general reduction of heat loss through the external building fabric, to inhibit heat loss.
Further Experimentation Arising From Current Analysis. Increased natural ventillation to further combat summer overheating and high humidity, resulting in better localised control of inhabitants and percieved thermal comfort. Increasing thermal mass of external walls. Improving u-values of windows could also be cause for exercise, however, due to the high performance of the low-e double glazed units simulated in the model, whose high peformance is recognised through recommendation of use in the Part L Building Regulations (2002), it seems likely that improvement is needed in the composition of the external wall. Shuttering / external shading on the glazed units could however be simulated, due to recent changes in design proposal to consider adding shuttering to windows to allow the inhabitant to adjust solar gains according to their individual comfort temperatures.
Model 3 With Macroflow Ventillation. With heating systems regulating the internal temperatures in winter months, the summer months prior to this model were solely regulated by thermal mass and as we saw from the considerable over heating, the regulation was minimal within these months. This simulation was being run with no circultion between rooms or ventillation out of the building. Introducing natural ventillation out of the building during summer months allows the building to increase cooling in times that it would otherwise overheat. This simulation was run to see the capability of ventillation alone to provide all the summer temperature regulation needs. Due to shutters intending to be added to the windows, the building is able to be naturally ventillated without cause for concern over security of the property; windows are able to be fully opened with the shutters locked securely. The simulation model was designed with windows (all external) at 50% openable area when the building gets to the opening threshold temperature of 23 degrees celsius (the point at which the inhabitant would open said windows). Because this is simulating the behavioural patterns of the inhabitants, this ventillation only occurs when the building is occupied, as set by the Annual Occupancy Profile. The doors (internal), are presumed open to 100% capacity during this period also, allowing cross ventillation within the building. due to the function of the building (private residential) it is likely that doors would be left open internally due to no cause for concern of considerable privacy amongst residents within the secured building.
MacroFlow Opening Types window as seen in the Building Template Manager (above)
RESULTS: MODEL 3 MACROFLOW. Dry resultant temperature range analysis: Hours per annum, that are recorded as 25 degress celsius or above. The below results are a fraction of the full 8760 days in the recorded year.
MODEL 3 WITH MACROFLOW
MODEL 3 PREVIOUS
KITCHEN LIVING STUDIO
39 28 41
4196 4311 4309
A considerable change from the simulated model without any natural ventillation applied. With natural ventillation the building is able to maintain a nearly constant comfortable temperature. These outstanding hours of 25 degrees or over could be completely irradicated by reducing the Opening Threshold Temperature further. It must be noted that these spikes away from the specified 23 degrees optiumum temperature in the summer months, can be altered in the real functioning of the building. The simulation of the natural ventillation can never be accurately simulated as the management of natural ventillation in reality is entirely down to the behavioural reactions of the inhabitants, and so temperature spikes would be avoided by the individual altering their ventillation scheme. The windows in this simulation being only opened to 50% capacity show scope to reduce this temperature further, and with greater reaction speed (thus reducing the spikes away from the comfort temperature).
Designing In Choice - Localized Control Mechanisms & The Variation Of Perceived Comfort. The 25 degrees opening threshold temperature was kept just above the optimum temperature 21 degrees celsius to allow for shutters to be added to the design. The addition of which would cause to decrease the internal temperatures further (as they are control mechanisms for reducing solar gains). These were not simulated as their design; moveable slats and two openable shutters, meant that the inhabitant has a great variation in localised control of the room temperature. This gives the user the ability to drop or increase the temperature of their home according to their needs. Perceived comfort temperatures vary and greater occupant satisfaction comes from the inhabitant being able to tailor their environment, their home, to their temperature needs. By allowing the users to do so increases their user satisfaction, and the building’s adaptability and resultant success. By performing a model that expresses temperature just over an average comfort level (21 degrees celsius), shows the building is thus adaptable. The heating in the winter months, is slightly below this due to the designer’s intention for users to “experience the seasons” and reduce energy loads of the building. This however, and like the cooling systems in the summer months can be adapted to the inhabitants needs. Being only heated for 4 hours total in the day, can be considerably increased to encourage higher temperatures.
Utilising IES software to further develop the sustainable design. Coursework. Student: Andrea Luise Schrader. Oxford Brookes University.