FXFOWLE Podium: Feasibility of Implementing Passivhaus Standard for Tall Residential Buildings

FEASIBILITY OF IMPLEMENTING THE

PASSIVHAUS STANDARD

FOR TALL RESIDENTIAL BUILDINGS

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Feasibility of Implementing the Passivhaus Standard for Tall Residential Buildings

Based on a study sponsored by NYSERDA (New York State Energy Research and Development Authority) Primary Sponsor: NYSERDA | Additional Sponsors: Roxul, Schรถck Team: FXFOWLE Architects, Dagher Engineering, Passive House Academy, Dharam Consulting, Simpson Gumpertz & Heger

Ilana Judah & Daniel Piselli | FXFOWLE

FEASIBILITY OF IMPLEMENTING THE

PASSIVHAUS STANDARD

FOR TALL RESIDENTIAL BUILDINGS

Ilana Judah, Int’l Assoc. AIA, OAQ, LEED AP, CPHD, Principal, FXFOWLE Daniel Piselli, AIA, LEED AP, CPHD, Senior Associate, FXFOWLE As populations grow and cities become larger and denser, problems related to energy inefficiency are magnified, threatening the sustainability of the world’s densest urban areas. Key to accommodating the world’s population boom, highly energy efficient and resilient buildings are also crucial to the success of dense urban environments. These areas are most affected by pollution, urban heat island effects, energy resource uncertainty, and stresses that cause health problems,

discomfort, economic hardship, and related challenges. In addition to these urban issues, global climate change, the ultimate energyrelated problem, poses an existential threat to all of the earth’s inhabitants.

Fortunately, it is possible to make buildings that demonstrate the level of energy efficiency needed to address these issues.

Contributing to this goal is Passivhaus, a standard originally developed for small buildings in the central European climate,

1 Passive NYC, (New York: Building Energy Exchange), 2015.

but now used internationally for buildings of all types, shapes and sizes, including new construction and retrofits. As a standard for energy efficient buildings, Passivhaus results in energy reductions for heating and cooling of approximately 70 to 90 percent compared to typical buildings1.

FXFOWLE recently led research to evaluate the applicability of the Passivhaus standard to tall residential buildings in one of the densest cities in North America, New York

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Feasibility of Implementing the Passivhaus Standard for Tall Residential Buildings

City (NYC). The research team proposed the study in order to investigate cutting-edge energy efficiency practices, to translate the Passivhaus standard from its European origins to local market, and to influence housing policy in New York towards more ambitious energy and greenhouse gas reduction targets.

The study is a comparative analysis of a basecase building design that targets a LEED v3 Silver rating to a Passivhaus design for the same building. The base-case building is a large, mixed-use multifamily housing project currently under construction:

85% reduction in heating demand 47% reduction in primary energy 2.4% capital cost increase

Preliminary results indicate that the Passivhaus design can significantly reduce energy use with virtually no aesthetic changes and with common construction methods (Figure 1). Results of the study show a 47 percent reduction in overall primary energy use as compared to the base-case building. Additional construction costs are estimated to be less than 2.5 percent with a payback of 24 years and significant capital cost replacement reductions.

These results strongly suggest that Passivhaus is applicable to tall residential buildings in NYC. Since New York has a challenging climate with cold winters and hot, humid summers, these results also suggest that Passivhaus is broadly applicable to cities in many climates.

This paper describes the research study in an abbreviated form. A full version of the report can be found at www.fxfowle.com.

PASSIVHAUS

5.2M 40-year NPV No major aesthetic changes Reduced mechanical equipment size Improved resiliency, acoustic performance and thermal comfort Typical New York City high-rise construction methods

The German term Passivhaus is often referred to in English as “Passive House.”

This paper uses the German term because the English word “house” can cause misperception that the standard is only for single-family houses. Passivhaus can be translated from German to a more applicable English phrase “Passive Building.”

The Passivhaus Standard was developed in Germany by The Passive House Institute and introduced in the early 1990s. It is based on a few simple principles and primarily architectural solutions to create ultra-lowenergy buildings. The five main Passivhaus principles include increased performance in: 1. Thermal insulation; 2. Thermal bridgefree design; 3. Air-tightness; 4. Passivhaus

Ilana Judah & Daniel Piselli | FXFOWLE

Figure 1:

Rendering by FXFOWLE

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Feasibility of Implementing the Passivhaus Standard for Tall Residential Buildings

Figure 2:

The five basic principles of Passivhaus.

windows; and 5. Mechanical ventilation with heat recovery (Figure 2). Other important strategies to achieve Passivhaus include optimized building orientation and window shading, passive solar gain, and reduced mechanical system sizes with increased efficiency.

Certification is based on a few crucial performance criteria as calculated by the Passivhaus Planning Package (PHPP) energy-modeling tool. Main criteria include very low energy consumption limits on heating demand (4.75 kBtu/{ft2yr}, 15kWh/ {m2yr}), cooling demand (5.39 kBtu/{ft2yr}, 17.02 kWh/{m2yr}), and total building primary energy demand (38.0 kBtu/ {ft2yr}, 120kWh/{m2yr}). In addition, a strict

Ilana Judah & Daniel Piselli | FXFOWLE

Figure 3:

Tall Passivhaus design (left to right): Atelier Hayde Architekten, RHW 2 Raiffeisen Konzernzentrale, Vienna, Austria, image©Herzi Pinki.

Ateliers Jean Nouvel, Police Headquarters, Charleroi, Belgium, image©Filip Dujardin.

Dattner Architects, 425 Grand Concourse, Bronx, NY, image ©Dattner Architects, Trinity Financial, MBD Community Housing Corporation.

Handel Architects, The House at Cornell Tech, New York, NY, image ©Handel Architects.

air-tightness limit must be achieved (0.6 ACH@50Pa, or 0.036 CFM/ft2, 0.183 l/{s/ m2}) of surface area for large buildings) and proven through blower door testing.

Buildings constructed to the Passivhaus Standard also benefit from improved indoor thermal comfort through reduced temperature asymmetry, better acoustic performance through enclosure upgrades, and higher air quality through increased ventilation and filtering of all supply air2.

The Intergovernmental Panel on Climate Change identified Passivhaus as one of the only whole-building strategies capable of reducing building energy use enough to achieve greenhouse gas mitigation targets for the building sector3 (IPCC, 2014). Municipalities in Germany, Austria, Belgium, and Spain have mandated

Passivhaus construction in various ways.

Passivhaus activity is now underway in the United States, China, and many other non-European countries with varied climatic conditions. To date, approximately 60,000 buildings adhere to the Passivhaus Standard4. These cover a wide range of locations and typologies including office, residential, schools, fire stations, healthcare facilities, convention centers, embassies, and research facilities.

While early Passivhaus projects were smallscale low-rise buildings, a number of large Passivhaus developments and tall buildings have emerged in the last few years. The new Bahnstadt district in Heidelberg, Germany, is an all-Passivhaus neighborhood that was partially complete at the time of publication.

The development includes a mix of building types including housing, commercial, and educational. Tall building examples include a 256-foot-tall (78-meter-tall) office tower in Vienna, Austria, and the 270-foot–tall (82.3-meter-tall) CornellTECH Residential dormitory in NYC. Multiple large Passivhaus buildings are proposed for locations from New York to Brussels to China (Figure 3). Cities will surely benefit as Passivhaus buildings of all types are shown to be viable throughout the world.

2 International Passive House Association, Active for more comfort: Passive House, (Darmstadt, 2014).

3 IPCC: Climate Change 2014: Synthesis Report, (Geneva, 2014), 45.

4 Passipedia, Examples, https://passipedia.org/examples, (2016).

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Feasibility of Implementing the Passivhaus Standard for Tall Residential Buildings

Figure 4:

Rendering by FXFOWLE

Ilana Judah & Daniel Piselli | FXFOWLE

Figure 5:

Representative New York City context.

BASE-CASE BUILDING FOR COMPARATIVE ANALYSIS The purpose of the research study is to assess the feasibility of designing high-rise residential buildings in New York City to the Passivhaus Standard. High-rise residential buildings are a building type in high demand, one that continues to fill the need for housing as populations grow in New York and cities around the world. The comparative analysis examines the impacts of achieving the standard from architectural, enclosure detailing, mechanical, constructability, resilience, zoning, and code and cost perspectives.

The base-case building is a 593,000-squarefoot (55,092-square-meter), 26-story multifamily mixed-use, high-rise building in Jamaica, Queens, one of New York’s five boroughs (Figure 4). The building targets

LEED v.3 Silver Certification and is currently under construction. Jamaica is well-served by transit. It hosts a regional transportation hub that includes bus, rail, and direct access to John F. Kennedy International Airport. The area is currently undergoing regeneration, and the city recently up-zoned the central district to enable higher density development. The base-case building is in the central district and immediately adjacent to the transportation hub. The building will serve as a model for mixedincome development with a combination of affordable and market-rate housing.

While the neighborhood context around the base-case building is currently low-rise construction, the study assumed built-out adjacent properties to represent a fully developed future condition. This step was necessary to approximate a typical New York City building site (Figure 5), and potential future overshadowing from adjacent buildings.

The site has a rail line and no structures to the

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Feasibility of Implementing the Passivhaus Standard for Tall Residential Buildings

south, which ensures adequate exposure for passive solar gain in winter The base-case building is currently under construction. The design targets LEED v.3 Silver Certification. The building includes a three-story retail podium and a 450-unit residential rental apartment tower with amenity spaces on the 4th and 25th floors.

The Passivhaus boundary, which identifies all areas to be accounted for in the energy model, includes all fully enclosed, conditioned space including retail, residential, and amenity areas.

Below-grade parking is the only area excluded from the Passivhaus boundary since it is not fully enclosed or conditioned.

Glazing is distributed across the building facades on all orientations based on apartment layouts. Shading devices are not used for specific South, East, or West solar conditions. The window-to-wall ratio is approximately 36 percent. This ratio is lower than many new market-rate residential buildings in New York City, where the current maximum prescriptive code glazing ratio is 40 percent. However, this ratio is higher than many affordable housing developments.

The predominant base-case exterior wall system is a cement-panel rain screen assembly supported on a metal frame backup wall. The residential tower has aluminum windows with double-glazed insulating glass units (IGUs) and operable in-swinging casement windows. Storefront and curtain wall fenestration occurs at the podium levels.The central plant of the basecase building provides space heating, space cooling, and domestic hot water. The original building design consists of a combined heat and power (CHP) system that operates in conjunction with hot water condensing

boilers and absorption chillers. To provide a more representative comparison, the basecase building central plant is modified: the CHP is removed, boilers are natural gas, and chillers are electric. There are three 350-ton (1231-kW) water-cooled electric chillers and eight 2550 MBH hot water boilers along with associated pumps and accessories. These provide chilled or hot water that is circulated through a dual temperature water loop throughout the building. For residential units, vertical stack fan coil units are served with chilled and hot water from the central plant to provide heating and cooling. Ventilation is provided through ducted openings in the exterior wall to the fan coil units. Central roof fans exhaust the toilets and kitchens.

Residential corridors utilize dedicated gas-fired, packaged air-cooled rooftop units with energy recovery for ventilation.

Energy recovery is achieved through toilet exhaust from apartments. Amenity areas are conditioned by horizontal and/or vertical fan coil units, provided with chilled and hot water from the central plant. LED lighting and Energy Star-rated appliances are used throughout the residential portion of the base-case building.

PASSIVHAUS DESIGN The Passivhaus redesign began with basic goals to make the result practical and replicable. The research team made a concerted effort to minimize changes to design and construction techniques.

Products and construction methods familiar to the current New York market were used.

No exotic systems or speculative products were required.

Potential Passivhaus energy balances were iterated in PHPP. Enclosure performance

Mechanical

Architectural

Ilana Judah & Daniel Piselli | FXFOWLE

Base Case

Iteration 1

Iteration 2

Passivhaus Design

Airtightness*

Pressurization Test @ 50 Pa

0.263 cfm/ft2

0.036 cfm/ft2

0.036 cfm/ft2

0.036 cfm/ft2

Insulation (Effective R-Value)

Roof Ground Floor Slab Basement Slab Rainscreen Wall (average) Brick Cavity Wall Lot Line Wall Foundation Wall Basement Wall

R 33.06 R 18.50 R0 R 12.02 R 10.71 R 15.90 R 4.34 R0

R 42.10 R 18.50 R 16.50 R 26.00 R 26.10 R 17.30 R 16.50 R 13.10

R 42.11 R 18.51 R 16.51 R 26.00 R 26.10 R 17.31 R 16.51 R 13.11

R 41.40 R 18.90 R 16.52 R 26.00 R 26.10 R 17.32 R 16.52 R 13.12

0.42 (R 2.4) 1.00 (R 1) 0.29 (R 3.4) 0.24 (R 4.2) 0.38 0.62

0.14 (R 7) 0.14 (R 7) 0.14 (R 7) 0.13 (R 7.5) 0.25 0.5

0.14 (R 7) 0.14 (R 7) 0.14 (R 7) 0.13 (R 7.5) 0.25 0.5

0.14 (R 7) 0.14 (R 7) 0.175 (R 5.7) 0.175 (R 5.7) 0.38 0.62

Windows U-Value

Frame

U-Value

Glass

SHGC

Residential Curtain Wall Residential Curtain Wall Residential Curtain Wall

Thermal Bridging

Ψ Typical Ψ Foundation χ Columns Ψ Balconies Ψ Windows & Doors χ Typical

0.15 0.15 1.2 0.556 0.15 1.2

<0.006 0.02 1 0.03 0.023 < 0.018

<0.006 0.02 1.0 0.03 0.023 < 0.018

<0.006 0.02 1.0 0.03 0.023 < 0.018

Ventilation

System Type

Energy Recovery Ventilator (ERV) for Corridors; Outside air provided directly to mechanical units without energy recovery for all other spaces

Multiple ERVs for all spaces (Semi Centralized System)

Multiple ERVs for all spaces (Semi Centralized System)

System Efficieny

Approximately 75% for Corridors; Not Applicable for all other spaces

Minimum 1 ERV (integrated into Heat Pump) for every apartment (Decentralized System); Multiple ERVs for all other spaces (Semi Centralized System) 80%

80%

85%

Mechanical System

System Description

Water-cooled Electric Chillers and Hot Water Boilers serving Two Pipe Fan Coil Units

Heat Pump, Heating Cooling and Hot Water Combined System in one unit per apartment; Seperated Heat Pump Cassettes Inline or Combined with PHI certified ERV’s

Water-cooled Electric Chillers Natural gas condensing Hot Water with magnetic bearing compressors Boilers serving Two Pipe Fan Coil Units

Central Plant Equipment

Cooling Efficiency

Electric Chillers, Hot Water Boilers, None and Cooling Towers 4.70 COP for Electric Chiller circa 2.00

Gas Powered CHP Cogen System feeding Hot Water system and Heating Coils with electrical generation for lighting and heat pump support. Heat pump heating and Hot water support with integration into ventialtion ductwork in a unique two part HRV/ERV system circa 2.50

Heating Efficiency

85% Thermal Eciency for Boilers

circa 1.80

Domestic Hot Water System Description

Indirect heat exchangers and storage tanks served by Boilers

Domestic Hot Water System Efficiency

Same as Heating Efficiency

Heat Pump, Heating Cooling and Indirect heat exchangers and Hot Water Combined System in one storage tanks served by Combined unit per apartment; Seperated Heat Heat and Power Units, also Pump Cassettes Inline or Combined supported by Heat Pump with PHI certified ERV’s circa 5.00 Circa 80 % with Cogen and 150% for Heat Pump Support

Lighting

Lighting in Apartments & Common Areas Lighting in Retail Spaces

20 FC @ 0.28 W/ft2 Avg.

0.14 W/ft2 Avg.

0.14 W/ft2 Avg.

60 FC @ 0.83 W/ft2 Avg.

0.25 W/ft2 Avg.

0.25 W/ft2 Avg.

60 FC @ 0.83 W/ft2 Avg.

Receptacle

Residential Recptacle Loads 0.50 W/ft2 Avg. Retail Recptacle Loads 1.35 W/ft2 Avg.

0.50 W/ft2 Avg. 1.35 W/ft2 Avg.

0.50 W/ft2 Avg. 1.35 W/ft2 Avg.

0.50 W/ft2 Avg. 1.35 W/ft2 Avg.

Table 1:

Comparison of PHPP inputs for base case, Iteration 1, Iteration 2, and Iteration 3 (based on the final Passivhaus design).

circa 3.00 circa 2.00

Electric Chillers, Hot Water Boilers, and Cooling Towers Peak condition: 0.61 kW/ton (COP 5.76); NPLV 0.352 kW/ ton for Electric Chiller 94.5% Thermal Efficiency for Boilers Natural gas condensing Water Heaters

95.5% Thermal Eciency 20 FC @ 0.28 W/ft2 Avg.

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Feasibility of Implementing the Passivhaus Standard for Tall Residential Buildings

targets were developed based on aggressive but achievable upgrades to base-case enclosure systems. Mechanical, Electrical & Plumbing (MEP) systems were analyzed in PHPP until a viable system achieved a Passivhaus energy balance (Table 1).

Architectural aspects of the Passivhaus redesign result in virtually no aesthetic changes. Architectural upgrades mostly occur at the level of details and specifications.

Improved performance is achieved through additional insulation, reduced thermal bridging, simplified air barrier installation strategies, and triple-glazed insulated windows. These changes allow mechanical systems to be substantially reduced or eliminated, thereby reducing first costs, operations and maintenance costs, and replacement costs.

The team preserved the base-case window-towall ratio of 36 percent. However, the windows were upgraded to include high-performance Passivhaus Certified triple glazing and enhanced thermally broken frames. Increased performance allowed window sizes and locations to remain unchanged despite un-optimized solar exposures and lack of shading devices. This achievement dispels a misperception that the team has sometimes encountered: that Passivhaus buildings do not have sufficient vision glass for views or daylight. Further, this result suggests that optimal building orientation, window exposure, and the addition of shading devices may allow Passivhaus buildings at the scale of the base-case building to achieve better performance with the same glazing ratio.

The research team redesigned all major enclosure assemblies in the base-case building to achieve the required performance.

A main area of focus was the predominant lightweight rain screen (Figure 6). The base-

case assembly is considered to perform better than average due to the use of intermittent aluminum attachment clips and more exterior continuous insulation than stud cavity insulation. This type of assembly has been shown to result in a 45 percent to 55 percent reduction of insulation effectiveness due to thermal bridging5. The Passivhaus energy balance required an effective insulation value of R-26 (IP U-0.0385, SI U-0.2184) for this assembly after accounting for thermal bridge reductions. A Passivhaus version of the assembly uses thermally improved fiberglass attachment clips and uninterrupted, continuous insulation. The improved assembly results in a lower, 20 percent reduction of insulation effectiveness6. This represents a 60 percent increase in insulation effectiveness over the base case. While this assembly achieves better performance, it is 3 inches (7.62 cm) thicker than the base-case assembly, and causes additional gross area and/or decreased usable area.

While the study used this assembly, an alternate was considered to address the undesirable impact on area. The alternate is based on a different fiberglass attachment clip that is reported to result in a 3 to 7 percent loss of insulation effectiveness. This represents a 90 percent increase in insulation effectiveness over the base case. This alternate approach allows some insulation to be shifted back into the metal stud cavity.

The resulting assembly is approximately 1 inch (2.54 cm) thicker than the base-case assembly, and minimizes additional gross and/or decreased usable area. Both improved assemblies reduce the potential for interior condensation by minimizing thermal bridging, and relocating insulation to the exterior. These measures shift the location of potential cold surfaces where condensation may occur to the exterior side of the weather barrier.

5 Payette, Thermal Performance of Facades, (Boston, 2014.)

6 Ibid.

Ilana Judah & Daniel Piselli | FXFOWLE

Figure 6:

1. Base case—Lightweight rain screen steel stud backup (R-17.65) 2. Passivhaus Proposal—Lightweight rain screen steel stud backup (R-26.0) 3. Alternate—Lightweight rain screen with steel stud and interior insulation

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Feasibility of Implementing the Passivhaus Standard for Tall Residential Buildings

In 2012, New York City launched the Zone Green zoning incentive to encourage the design of high-performance enclosures and other energy savings measures. This incentive enables a portion of exterior wall to be excluded from zoning calculations if the wallâ&#x20AC;&#x2122;s thermal performance exceeds code requirements. Up to eight inches (20.32 cm) of exterior wall can be deducted after the first eight inches of wall thickness.

The proposed Passivhaus details would enable the project to benefit from the maximum deduction permitted by the incentive. In providing the opportunity to increase the available Zoning Floor Area for development, this kind of incentive is highly influential in encouraging developers to provide more highly insulated exterior walls, and can be emulated in other jurisdictions.

All major details in the base-case building are redesigned to enable airtight installation and reduce thermal bridging. Common air and vapor barrier products are used. Basecase building window closure details rely on sealant, which may crack over time. The Passivhaus design proposes self-adhered membrane flashing instead of sealant to improve the consistency of workmanship at joints between window frames and rough openings, and similar construction joints.

Thermal bridge reduction strategies include the use of structural thermal breaks at balconies and parapets, proper positioning of window thermal breaks with assembly insulation layers, stand-off metal shelf angles, and discontinuous through-wall flashings (Figure 7). Calculated thermal bridge values were used when Passivhaus thermal bridge maximums could not be achieved.

The Passivhaus MEP design is a modification of the base-case building system. Similar

components are used such as vertical fan coil units, water-cooled chillers, cooling towers and condensing boilers. However, greatly reduced heating and cooling loads enable the HVAC equipment to operate at optimum efficiency and to be specified at reduced sizes. Energy recovery ventilation units with a minimum efficiency of 85 percent are used for ventilation of all conditioned spaces.

Chillers are changed from an electric system with a coefficient of performance (COP) of 4.70 to high efficiency magnetic bearing compressors with Variable Frequency Drives (COP 5.76). With reduced envelope heat losses, fan coil units in the apartments are capable of providing adequate heating even with low hot water temperatures of 105 degrees Fahrenheit (40.56 C) supply and 95 degrees Fahrenheit (35.0 C) return. These low temperatures enable the condensing boilers to operate at an optimum efficiency of 94.5 percent, compared to 85 percent efficiency in the base-case building.

Ventilation with energy recovery is a key component to the Passivhaus design, permitting almost all energy in the exhaust air to be recovered and used to precondition incoming outside air. The tower portion of the base-case building utilized louvers on the facade to provide outside air to fan coil units in apartments. Apartment fan coil units did not utilize energy recovery. That inefficient system for ventilation was revised to ultra-efficient Passivhaus Certified energy recovery units mounted on the roof, with each unit serving multiple apartments. A small amount of additional shaft space was needed in each apartment to accommodate ventilation ducts. Amenity, lobby and retail spaces are served by separate ERV units (Figures 8 & 9). Balancing of the ventilation system is assisted by the use of spray sealant

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Ilana Judah & Daniel Piselli | FXFOWLE

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Feasibility of Implementing the Passivhaus Standard for Tall Residential Buildings

Figure 8:

Heating, cooling and ventilation in Passivhaus Proposal

inside ducts and constant airflow regulators.

The regulators also help limit potential stack effect disruption of ventilation flows.

ANALYSIS PHPP analysis shows a successful Passivhaus design (Table 2). The total primary energy savings is in line with general expectations of the Passivhaus Standard. Compared to the base-case

building, the Passivhaus design resulted in greater energy reductions in heating than in cooling due to the specific nature of the base-case design and the NYC climate.

It is likely that buildings with different mechanical systems or buildings in other climates will require different proportions of heating and cooling energy reductions. The greatest challenge in meeting the overall energy targets related to appliance and receptacle loads. The high density of large buildings represents a greater number of kitchen appliances per square foot than

Ilanaâ&#x20AC;ŻJudah & Daniel Piselli | FXFOWLE

ERV 1 - Residential Units ERV 2 - Residential Units

ERV 5 - Residential Units

ERV 3 - Residential Units

ERV 6 - Residential Units

ERV 4 - Residential Units

ERV 7 - Residential Units ERV 8 - Corridor

ERV 9 - Amenity ERV 10 - Residential Lobby ERV 11 - Bicycle Storage

ERV 12, 13 - Misc. Residential Service Areas

Space for Retail ERV by Future Tenant Space for Retail ERV by Future Tenant Space for Retail ERV by Future Tenant

ERV 14 - Comm. Storage

Figure 9:

Ventilation Zone Diagram

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Feasibility of Implementing the Passivhaus Standard for Tall Residential Buildings

PHPP Modeling Comparison

Passivhaus Requirement Passivhaus Design PHPP Fulfilled? Savings Over Base-Case

Base-Case PHPP

Heating Demand

4.75 kBtu/(ft2yr)

2.86 kBtu/(ft2yr)

Yes

85%

19.72 kBtu/(ft2yr)

Heating Load

3.17 Btu/(ft2hr)

2.34 Btu/(ft2hr)

Yes

77%

10.29 Btu/(ft2hr)

Cooling Demand

5.39 kBtu/(ft2yr)

4.65 kBtu/(ft2yr)

Yes

40%

7.73 kBtu/(ft2yr)

Cooling Load

3.17 Btu/(ft2hr)

2.67 Btu/(ft2hr)

Yes

37%

4.22 Btu/(ft2hr)

Primary Energy*

38.0 kBtu/(ft2yr)

37.7 kBtu/(ft2yr)

Yes

47%

70.80 kBtu/(ft2yr)

Airtightness**

0.036 cfm/ft2@50Pa

0.036 cfm/ft2@50Pa

Yes

86%

0.263 cfm/ft2@50Pa

Passivhaus?

Yes

*Primary energy includes heating, cooling, dehumidification, DHW, auxiliary electricity, lighting, and electrical applicances. **Pressurization test result n50

Table 2:

a smaller-scale building. Therefore, very efficient products are required to meet the targets.

performance. The study assumes additional time for construction for additional due diligence for installation of all components of the building enclosure, ductwork air sealing and testing, and air barrier testing and repair.

Construction: The main challenge in constructing a Passivhaus building similar to the proposed design is expected to be the quality of workmanship required to achieve airtightness requirements. While the same construction techniques are used in the base-case and Passivhaus design, attentiveness of the workforce and coordination between trades is crucial to the successful installation of the air barrier. The study proposes increased scrutiny of the air barrier through the use of the Air Barrier Association of America (ABAA) quality procedures, accredited professionals and auditing procedures to ensure proper design, installation and testing.

ABAA recommendations include utilizing a third party air barrier consultant, and air barrier shop drawings. Blower door testing is necessary to control quality and to prove

Resilience: The Passivhaus design will improve overall building resilience. Increased insulation, thermally broken triple-pane windows, and significantly improved air-tightness will enable these buildings to remain comfortable during a power outage for a longer period of time than those built using conventional construction methods.

A study was recently undertaken after Hurricane Sandy caused power outages and unsafe building conditions in NYC. The study concluded that an extended power outage in summer or winter would cause typical high-rise apartment buildings to reach unsafe temperatures in one to three days, while high-performance buildings similar to the proposed Passivhaus design would remain habitable for a week or more7. Passivhaus strategies such as

Passivhaus Design PHPP Results

7 Urban Green Council, Baby Itâ&#x20AC;&#x2122;s Cold Inside, (New York, 2014.)

Ilanaâ&#x20AC;ŻJudah & Daniel Piselli | FXFOWLE

operable windows, increased insulation, and improved air tightness help control passive heat gain and heat lost during power outages.

Financial analysis: Dharam Consulting performed a cost analysis to compare the base-case building and Passivhaus design. Specific energy conservation measures were identified and costs for those items were assigned for both the base-case and Passivhaus design options.

This side-by-side comparison enabled a clear cost analysis. The Passivhaus design was found to increase capital costs by 2.4 percent. The annual energy cost savings in the Passivhaus design as compared to the base case results in a 24 year simple payback and a Net Present Value (NPV) savings of $5.2 million after 40 years. Additional costs were primarily for the building envelope, general construction management and additional contingencies, while savings were captured in the reduced MEP systems. The largest cost increase was for the Passivhaus Certified windows. It should be noted that first cost estimates for the Passivhaus design were conservative and can be reconsidered to lower costs even further. For example, less expensive but still high performing window frames could be selected to reduce costs.

Increased costs for general conditions were also conservatively estimated and could be reduced with a knowledgeable contractor.

With lower cost windows, a tighter schedule, and some modification to the aesthetics, a payback of under10 years could be achieved.

CONCLUSION The findings of this study suggest that high-rise residential buildings in NYC can be designed to the very high levels of energy efficiency and resilience that Passivhaus establishes. This can be achieved with minor

aesthetic adjustments and reasonable glazing ratios. Financially, achieving the standard appears financially viable, and will become increasingly more cost effective as the design and construction industry becomes more experienced and familiar with Passivhaus.

A number of challenges confront the implementation of Passivhaus in New York City and globally. As the standard was developed in central Europe, addressing local issues will enable worldwide application of the standard. Varying climatic conditions, construction practices, labor quality, product availability, codes, and cultural use patterns will result in different solutions in each location. Collaboration between the Passivhaus certifying body, local regulatory agencies, designers, and developers is critical. Financial and zoning incentives will also go a long way to shift the paradigm towards this ultra-low energy approach.

Passivhaus represents a breakthrough in energy efficient building design that offers a significant opportunity for cities to become more sustainable, healthier places.

European cities are already starting to include Passivhaus in building codes. New York has now introduced the standard as one path to achieve low-energy compliance for new city buildings. As Passivhaus is proven to be feasible globally, municipalities around the world can also consider mandating this highly energy efficient and resilient approach.

This study shows how Passivhaus can be implemented in New York City for a single building typology. To prove this approach is globally viable, architects and developers around the world must launch similar studies and pilot projectsâ&#x20AC;&#x201D;many such projects are already underway.

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Feasibility of Implementing the Passivhaus Standard for Tall Residential Buildings

Ilana Judah & Daniel Piselli | FXFOWLE

Ilana Judah is Principal and Director of Sustainability at FXFOWLE Architects.

An architect with 20 years of experience, she believes in the importance of education, research and public advocacy in improving our environment. Ms. Judah leads sustainability visioning and strategy implementation for local and global projects of multiple scales and typologies. A Certified Passive House Designer, she is a board member of New York Passive House and served on New York City’s 80x50 Technical Working Group. A recognized industry leader, she has taught at Cornell, Columbia, New York University, and University of Pennsylvania.

Daniel Piselli is a Senior Associate and Project Architect at FXFOWLE Architects.

He has over 18 years of experience leading teams on a wide variety of project types located in the United States and the Middle East–including metro stations, bridges, schools, offices, and residential buildings among others. Daniel is currently Project Architect for The Statue of Liberty Museum.

His passion is to create transformative architecture by focusing on the design of exterior envelopes and sustainability to minimize energy use. As a Certified Passive House Designer, Daniel is leading the firm’s efforts to utilize Passive House standards in large-scale buildings. In addition to his project work at FXFOWLE, he has served on the Board for the Bird-Safe Glass Foundation for the past several years.

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