The Passive House Approach The Passive House
Stories from the field ▪ ACI Celebrates 25 years ▪ Cash for appliances MAR/apr 2011
$15
The Passive House Approach
Green the Orange The Robo House Raising the Bar for Home Performance
Green the Orange
Multifamily Performance Program The NYSERDA Multifamily Performance program addresses the needs of the multifamily sector by bringing developers, building owners, and building and energy professionals together to improve the energy efficiency, health, safety, and security of residential buildings with five or more residential units in a cost-effective manner. The program has New Construction and Existing Building components, serving all combinations of market-rate and low- to moderate-income projects through a common process and varying schedule of incentives. The NYSERDA program relies on an approved network of building performance specialists who have demonstrated the ability to provide multifamily building performance services. These professionals are identified as Multifamily Performance Partners. To learn more about the NYSERDA Multifamily
SWA
Performance program, go to www.nyserda.org.
by Karla DonNelly, Jim Gunshinan, and Gayathri Vijayakumar
S
tudent life at Syracuse University can be comfortable as well as energy efficient. University Village Apartments includes five buildings and 120 apartments for students. The project, developed by Education Realty Trust on land leased from the university, achieved Gold certification under the LEED for Homes rating system. Each apartment in the project earned the Energy Star and each building received incentives under the New York State Energy Research and Development Agency (NYSERDA) Multifamily Performance program as its third Low Rise Pilot participant (see “Multifamily Performance Program”). “Prospective residents are usually first attracted by all of the great features of our apartments and our fitness center, study rooms, and theater, but they perk up during the tour when they hear about the insulation, water, and electrical features that help reduce the cost of their utilities and save the environment,” says Matt Burkett, community manager at University Village Apartments on Colvin. “A high percentage of our residents participate in day-to-day recycling as well as special events hosted here to support envi32
Home Energy
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M ar c h / A pr il 2 0 1 1
ronmental efforts on campus,” adds Burkett. “We think they are inspired to do more because of where they live.” “During our first week of move-in, we were given training and education materials that really delved into the background of the buildings,” says Jason Flores, a resident at University Village on Colvin. “This made choosing to live here that much better. As far as comfort level goes, I wouldn’t have noticed the difference if I hadn’t been told about the measures taken, they are that seamless. In fact, in this area, not too many people even have central air or adequate and efficient heat, so the ‘green’ lifestyle is actually more comfortable!” Steven Winter Associates (SWA), for whom coauthor Karla Donnelly works, is a Multifamily Performance Partner and served as the LEED for Homes provider, HERS rater, and sustainability consultant on this project. The architectural firm Holmes King Kallquist joined with general contractor Haynor Hoyt to manage the construction of the slab-on-grade, fully panelized, wood-framed, three-story buildings that make up University Village. SWA partner Northeast Green Building
multifamily
The Buildings The following is a description of Building 1, which has 24 twobedroom units. The construction details are identical to those in the other four buildings that make up University Village, though the others each have 24 four-bedroom, four-bathroom units. There are eight units per floor. Each floor has four 949 ft 2 apartments and four 1,048 ft 2 apartments. All of the units in Building 1 have two bedrooms, two bathrooms, a kitchen, a living room, and in-unit laundry. The foundation is slab-on-grade, with R-10 rigid insulation extending 4 feet vertically around the footing wall rather than horizontally under the slab. The walls are constructed with 6-inch-wide prefabricated plywood panels with 2 x 6, 16-inch OC wood studs. Walls were insulated onsite with R-21 fiberglass batts, and rim joists were insulated with high-density closed-cell spray foam. Energy Star-qualified vinylclad windows (U .31, SHGC .30) were installed, and 10 inches of blown-in cellulose was used in the attic to achieve R-38. There are four staircases and four exterior doors to common corridors for apartment access. There are no elevators. Each corner unit has 675 square feet and each inside unit has 370 square feet exterior wall area of conditioned space. The total gross window area of each unit is 85 square feet. There are four mechanical closets per floor (servicing two apartments each). The corridors and stairs are within the thermal envelope and are indirectly conditioned by these mechanical rooms but are not directly heated, cooled, or ventilated. The heating system for each apartment is a 40,000 Btu-perhour Energy Star-qualified natural-gas furnace, with an AFUE
Annual Gas Consumption
Natural Gas (Therms)
Consulting (NGBC) helped the builder improve envelope tightness significantly over standard practice, through air sealing training and testing. Construction was completed in the summer of 2009, and students were able to move in for the start of the fall semester. SWA has evaluated energy consumption data on the five buildings for over a year and is able to compare actual energy use in the buildings with the energy use predicted by the energy model.
Figure 1. Building 1 is the one with two bedroom units, which is why its energy use is lower. Gas bills show more energy use than the REM model, perhaps because of a difference in thermostat settings (the model assumes 68°F).
Annual Electricity Consumption
Electricity (kWh)
SWA
Separately metered apartments allow residents to participate in lowest energy consumption competitions.
(annual fuel utilization efficiency) of 92%. Seven-day programmable thermostats are installed in each unit. The domestic hotwater system for each apartment is a 66-gallon stand-alone electric water heater with a 0.92 energy factor. Cooling for each apartment is provided by 14 SEER, Energy Star-qualified split-system air conditioners. A 1.5-ton unit was installed for each of the first- and second-floor apartments (16 units total), and a 2-ton unit was installed for each of the thirdfloor apartments (8 units total). They were sized according to ACCA Manual J and S. Rightsizing is a LEED for Homes and Energy Star requirement. It provides better dehumidification in the summer, reduces equipment short-cycling, and is cheaper
Figure 2. Electric bills show less energy use than does REM modeling. This could be related to low occupancy in the summer (lower cooling energy consumption) and the default assumptions in REM for plug loads. REM uses default water consumption (although these units had low-flow fixtures, reducing hot water needs), and REM has a default setting to calculate installed lighting. Although we can indicate in REM the percentage of lighting that is fluorescent, it’s possible that the total watts and operating hours modeled are higher than actual use. w w w. h o m e e ner g y.o r g
33
Billing Period
34
Common Area Daily Electrical Usage
Average Daily Electric Use (kWh)
Average Daily Electric Use (kWh)
Total Apartment Daily Electrical Usage
Billing Period
Figure 3. The baseload—orange dashed line—is generally assumed to be the consumption in a shoulder month, since this usually indicates a month without heating or cooling. However, in student housing, this may not be the case. It’s possible that the months with the lowest use here are months in which the apartments are not fully occupied. This makes it difficult to break down consumption by end use.
Figure 4. Monthly electric usage in common areas—orange dashed line shows our estimated baseload, which SWA knows in these buildings is only lighting (stairs and Exit signs, 24/7, and corridors on sensors). The excess in the shoulder and winter months is for the 3 kW electric heaters in the vestibules. SWA estimated that the corridor lights would be on about 18 hours a day instead of 24, due to the sensors. The bills show that they are on much less—only 3–4 hours.
than buying oversized equipment that is not needed. MERV 8 filters, another LEED for Homes requirement, provide goodquality air filtration. An exhaust fan pulling a continuous 30 CFM from each of the two bathrooms provides mechanical exhaust ventilation in each apartment. A 19W rooftop fan serves each of the thirdfloor apartments, and a 19W sidewall ventilation system is used for each of the first and second floors. This satisfies the minimum requirement for good indoor air quality as established by ASHRAE Standard 62.2-2004, which requires a minimum 35 CFM continuous whole-house ventilation for apartments of this size, as well as 25 CFM continuous local exhaust per bathroom. A tenant-operated range hood, vented to the exterior, provides the ASHRAE-required local exhaust in each apartment kitchen. Individual apartments passed rigorous tightness testing to verify minimal air transfer—as well as sound and odor transfer—between the adjoining apartments, and between the apartments and the exterior. In addition, contractors tightly sealed ductwork to reduce duct leakage below 6 CFM/100 square feet of conditioned floor area. SWA engineer, Gayathri Vijayakumar determined baseline building components using RESNET standards, the 2006 International Energy Conservation Code (IECC), and NYSERDA guidelines. To qualify for the NYSERDA Multifamily Performance program, an energy efficiency measure is one that improves new building performance when compared to the baseline building. The energy savings for these combined measures must represent a 20% reduction in annual energy costs over the baseline building in order for the building to qualify for NYSERDA’s incentives. To earn the Energy Star from EPA, each apartment needed to achieve a HERS index of less than 80. The following energy efficiency measures were evaluated but not installed:
▪ One and one-half-inch closed-cell spray foam plus R-11 fiber-
Home Energy
|
M ar c h / A pr il 2 0 1 1
glass batt insulation for above-grade walls. This cost upgrade was $8,815 for the building. Instead of implementing this measure, SWA trained the builder in air-sealing techniques using R-19 fiberglass batts alone. In hindsight, the additional labor and time needed to air seal the building properly might have cost more than using spray foam to flash and batt. ▪ R-10 rigid insulation under the entire slab. The builder installed R-10 rigid insulation around the perimeter of the slab rather than under the slab because during construction, the rigid insulation can be crushed and broken if the workers walk on it before the slab is poured. ▪ Heat recovery ventilators. The additional ductwork and expense of installing an HRV for each unit was beyond the scope of the budget. Instead, common bathroom exhaust fans were used to provide continuous ventilation for each unit. ▪ Energy Star-qualified bathroom exhaust fans, with boost capability. These exhaust fans can be set to run continually at a lower CFM to satisfy the requirements for whole-house ventilation (35 CFM for two-bedroom units, 55 CFM for fourbedroom units) and can boost to 80 CFM for spot ventilation. However, this measure would have cost an extra $135 per fan for 432 fans, or over $58,000. This was beyond the scope of the budget. Measured Performance Monthly gas use data are available for each building, and electric use data are available for each of the 120 apartments. Natural gas is used only for the furnaces serving each apartment, but it is billed at the building level. Everything else is electric. There is one meter for each apartment and two meters covering the common area in each of the five buildings.
SWA
The Energy Information Agency regularly publishes Residential their rated capacity. The contractors reduced the flows, thereby Energy Consumption Survey (RECS) data. In 2005, these data show minimizing the energy loss associated with exhausting an exthat average energy use for all residential buildings in New York State, cess of ventilation air. Field testing by the HERS raters to verify including single-family and multifamily buildings, was 60,000 Btu kitchen exhaust, bath exhaust, duct leakage, and unit tightness per square foot per year. For multifamily buildings in the United States helped the contractors to identify problems and address them. Scheduling inspections and coordinating with all the trades with five or more two-bedroom apartments, the RECS data show average energy use of 62,000 Btu per square foot per year. Though is a challenge with multifamily buildings. For example, insulathe findings cannot be directly compared with the RECS data, SWA tion was moved in order to install a sprinkler system after the found average energy consumption of 40,000 Btu per square foot per insulation was inspected. Obviously, the insulation inspection year for the apartments in the building with two-bedroom units, and should have been done after the sprinklers were installed, but average energy consumption of 37,000 Btu per square foot per year for with dynamic schedules, this can be difficult to coordinate, and both jobs must be done bethe apartments in the buildings with fore the drywall is installed. The four-bedroom units. use of electric-resistance heaters To calculate energy cost savis questionable, given the ineffiings for the NYSERDA program, ciency of the source of electricity. the electric-resistance unit heaters However, the additional cost and in the entryways (four per buildcomplexity of running gas lines ing) were assumed to operate at for these small vestibule heaters 3 kW for 9 hours per day for 120 made gas an ineffective alternadays (that’s the lowest setting, and tive. Stairwell lighting was inithe thermostats were set to 55°F). A tight build-out schedule was kept by setting panelized walls on tially in excess of lighting allowThis was just an estimate; bills insulated slabs. ances, especially since there are show that they are actually operating much less. Lights in the stairway were assumed to operate windows in the stairwells. Photosensors and motion sensors 24/7 and lights in the corridors were assumed to operate for 18 were evaluated, but ultimately the fixtures were modified to hours per day, since they have motion sensors. Again, the bills use one lamp, rather than two, effectively reducing lighting are showing that the common-area lights are operating much consumption by 50%. While spray foam would otherwise have been a good choice less—9 hours per day rather than the predicted 18. The electricresistance heaters also operated much less than we expected—3 for the exterior walls, the challenge of building multifamily housing is the interconnectedness between apartments. The or 4 hours per day rather than 9. Figures 1 and 2 (p. 33) show actual annual gas and electricity builders realized that a flash-and-batt system would probably use for the University Village buildings compared to modeled, have been cost-effective, since they spent so much time air sealor predicted, energy use during one year. REM/Rate was in the ing. A flash-and-batt system would work well as long as the inright ballpark for heating and cooling consumption (in reality, stallers paid close attention to connections from apartment to occupants tend to use a bit more energy here than was predicted apartment, with particular emphasis on duct sealing and leakage to shared mechanical closets. by the model). The project team made a late decision to pursue LEED Gold cerFigure 3 shows average daily apartment electricity use by month. There is a surge in consumption in the heating season. tification. Despite some hang-ups with ventilation and air sealing, SWA attributes this surge to the air handlers. Also, since our the project team was able to achieve LEED Gold on a tight schedutility bill analysis assumes constant occupancy year-round, ule because the architect and the general contractor remained and many of the apartments are vacant in the summer, some of in close communication and because they were both willing to the extra winter electricity use may actually be going for base- learn a new program. On-site training provided by NGBC was also load and not for heating. Common-area electricity consump- crucial. It enabled the trades to work in an integrated way, and it tion was definitely overestimated (see Figure 4). helped them to understand what they needed to do to maximize whole-building performance. Lessons Learned >> For more information: As is often the case with multifamKarla Donnelly is a LEED AP Homes and To learn more about Steven Winter ily projects, air sealing and ventilation LEED Green Rater working in SWA’s residenAssociates, go to www.swinter.com. proved challenging at first. A redesign tial programs. Jim Gunshinan is the editor Contact Karla Donnelly at kdonnelly@ for continuous bath exhaust to meet of Home Energy. Gayathri Vijayakumar is swinter.com and Gayathri Vijayakumar at ASHRAE 62.2 originally led to overvena mechanical engineer performing [email protected]. tilation when fans performed beyond tial energy analysis for SWA. 36
Home Energy
|
M ar c h / A pr il 2 0 1 1
$15
The Passive House Approach
Green the Orange The Robo House Raising the Bar for Home Performance
Green the Orange
Multifamily Performance Program The NYSERDA Multifamily Performance program addresses the needs of the multifamily sector by bringing developers, building owners, and building and energy professionals together to improve the energy efficiency, health, safety, and security of residential buildings with five or more residential units in a cost-effective manner. The program has New Construction and Existing Building components, serving all combinations of market-rate and low- to moderate-income projects through a common process and varying schedule of incentives. The NYSERDA program relies on an approved network of building performance specialists who have demonstrated the ability to provide multifamily building performance services. These professionals are identified as Multifamily Performance Partners. To learn more about the NYSERDA Multifamily
SWA
Performance program, go to www.nyserda.org.
by Karla DonNelly, Jim Gunshinan, and Gayathri Vijayakumar
S
tudent life at Syracuse University can be comfortable as well as energy efficient. University Village Apartments includes five buildings and 120 apartments for students. The project, developed by Education Realty Trust on land leased from the university, achieved Gold certification under the LEED for Homes rating system. Each apartment in the project earned the Energy Star and each building received incentives under the New York State Energy Research and Development Agency (NYSERDA) Multifamily Performance program as its third Low Rise Pilot participant (see “Multifamily Performance Program”). “Prospective residents are usually first attracted by all of the great features of our apartments and our fitness center, study rooms, and theater, but they perk up during the tour when they hear about the insulation, water, and electrical features that help reduce the cost of their utilities and save the environment,” says Matt Burkett, community manager at University Village Apartments on Colvin. “A high percentage of our residents participate in day-to-day recycling as well as special events hosted here to support envi32
Home Energy
|
M ar c h / A pr il 2 0 1 1
ronmental efforts on campus,” adds Burkett. “We think they are inspired to do more because of where they live.” “During our first week of move-in, we were given training and education materials that really delved into the background of the buildings,” says Jason Flores, a resident at University Village on Colvin. “This made choosing to live here that much better. As far as comfort level goes, I wouldn’t have noticed the difference if I hadn’t been told about the measures taken, they are that seamless. In fact, in this area, not too many people even have central air or adequate and efficient heat, so the ‘green’ lifestyle is actually more comfortable!” Steven Winter Associates (SWA), for whom coauthor Karla Donnelly works, is a Multifamily Performance Partner and served as the LEED for Homes provider, HERS rater, and sustainability consultant on this project. The architectural firm Holmes King Kallquist joined with general contractor Haynor Hoyt to manage the construction of the slab-on-grade, fully panelized, wood-framed, three-story buildings that make up University Village. SWA partner Northeast Green Building
multifamily
The Buildings The following is a description of Building 1, which has 24 twobedroom units. The construction details are identical to those in the other four buildings that make up University Village, though the others each have 24 four-bedroom, four-bathroom units. There are eight units per floor. Each floor has four 949 ft 2 apartments and four 1,048 ft 2 apartments. All of the units in Building 1 have two bedrooms, two bathrooms, a kitchen, a living room, and in-unit laundry. The foundation is slab-on-grade, with R-10 rigid insulation extending 4 feet vertically around the footing wall rather than horizontally under the slab. The walls are constructed with 6-inch-wide prefabricated plywood panels with 2 x 6, 16-inch OC wood studs. Walls were insulated onsite with R-21 fiberglass batts, and rim joists were insulated with high-density closed-cell spray foam. Energy Star-qualified vinylclad windows (U .31, SHGC .30) were installed, and 10 inches of blown-in cellulose was used in the attic to achieve R-38. There are four staircases and four exterior doors to common corridors for apartment access. There are no elevators. Each corner unit has 675 square feet and each inside unit has 370 square feet exterior wall area of conditioned space. The total gross window area of each unit is 85 square feet. There are four mechanical closets per floor (servicing two apartments each). The corridors and stairs are within the thermal envelope and are indirectly conditioned by these mechanical rooms but are not directly heated, cooled, or ventilated. The heating system for each apartment is a 40,000 Btu-perhour Energy Star-qualified natural-gas furnace, with an AFUE
Annual Gas Consumption
Natural Gas (Therms)
Consulting (NGBC) helped the builder improve envelope tightness significantly over standard practice, through air sealing training and testing. Construction was completed in the summer of 2009, and students were able to move in for the start of the fall semester. SWA has evaluated energy consumption data on the five buildings for over a year and is able to compare actual energy use in the buildings with the energy use predicted by the energy model.
Figure 1. Building 1 is the one with two bedroom units, which is why its energy use is lower. Gas bills show more energy use than the REM model, perhaps because of a difference in thermostat settings (the model assumes 68°F).
Annual Electricity Consumption
Electricity (kWh)
SWA
Separately metered apartments allow residents to participate in lowest energy consumption competitions.
(annual fuel utilization efficiency) of 92%. Seven-day programmable thermostats are installed in each unit. The domestic hotwater system for each apartment is a 66-gallon stand-alone electric water heater with a 0.92 energy factor. Cooling for each apartment is provided by 14 SEER, Energy Star-qualified split-system air conditioners. A 1.5-ton unit was installed for each of the first- and second-floor apartments (16 units total), and a 2-ton unit was installed for each of the thirdfloor apartments (8 units total). They were sized according to ACCA Manual J and S. Rightsizing is a LEED for Homes and Energy Star requirement. It provides better dehumidification in the summer, reduces equipment short-cycling, and is cheaper
Figure 2. Electric bills show less energy use than does REM modeling. This could be related to low occupancy in the summer (lower cooling energy consumption) and the default assumptions in REM for plug loads. REM uses default water consumption (although these units had low-flow fixtures, reducing hot water needs), and REM has a default setting to calculate installed lighting. Although we can indicate in REM the percentage of lighting that is fluorescent, it’s possible that the total watts and operating hours modeled are higher than actual use. w w w. h o m e e ner g y.o r g
33
Billing Period
34
Common Area Daily Electrical Usage
Average Daily Electric Use (kWh)
Average Daily Electric Use (kWh)
Total Apartment Daily Electrical Usage
Billing Period
Figure 3. The baseload—orange dashed line—is generally assumed to be the consumption in a shoulder month, since this usually indicates a month without heating or cooling. However, in student housing, this may not be the case. It’s possible that the months with the lowest use here are months in which the apartments are not fully occupied. This makes it difficult to break down consumption by end use.
Figure 4. Monthly electric usage in common areas—orange dashed line shows our estimated baseload, which SWA knows in these buildings is only lighting (stairs and Exit signs, 24/7, and corridors on sensors). The excess in the shoulder and winter months is for the 3 kW electric heaters in the vestibules. SWA estimated that the corridor lights would be on about 18 hours a day instead of 24, due to the sensors. The bills show that they are on much less—only 3–4 hours.
than buying oversized equipment that is not needed. MERV 8 filters, another LEED for Homes requirement, provide goodquality air filtration. An exhaust fan pulling a continuous 30 CFM from each of the two bathrooms provides mechanical exhaust ventilation in each apartment. A 19W rooftop fan serves each of the thirdfloor apartments, and a 19W sidewall ventilation system is used for each of the first and second floors. This satisfies the minimum requirement for good indoor air quality as established by ASHRAE Standard 62.2-2004, which requires a minimum 35 CFM continuous whole-house ventilation for apartments of this size, as well as 25 CFM continuous local exhaust per bathroom. A tenant-operated range hood, vented to the exterior, provides the ASHRAE-required local exhaust in each apartment kitchen. Individual apartments passed rigorous tightness testing to verify minimal air transfer—as well as sound and odor transfer—between the adjoining apartments, and between the apartments and the exterior. In addition, contractors tightly sealed ductwork to reduce duct leakage below 6 CFM/100 square feet of conditioned floor area. SWA engineer, Gayathri Vijayakumar determined baseline building components using RESNET standards, the 2006 International Energy Conservation Code (IECC), and NYSERDA guidelines. To qualify for the NYSERDA Multifamily Performance program, an energy efficiency measure is one that improves new building performance when compared to the baseline building. The energy savings for these combined measures must represent a 20% reduction in annual energy costs over the baseline building in order for the building to qualify for NYSERDA’s incentives. To earn the Energy Star from EPA, each apartment needed to achieve a HERS index of less than 80. The following energy efficiency measures were evaluated but not installed:
▪ One and one-half-inch closed-cell spray foam plus R-11 fiber-
Home Energy
|
M ar c h / A pr il 2 0 1 1
glass batt insulation for above-grade walls. This cost upgrade was $8,815 for the building. Instead of implementing this measure, SWA trained the builder in air-sealing techniques using R-19 fiberglass batts alone. In hindsight, the additional labor and time needed to air seal the building properly might have cost more than using spray foam to flash and batt. ▪ R-10 rigid insulation under the entire slab. The builder installed R-10 rigid insulation around the perimeter of the slab rather than under the slab because during construction, the rigid insulation can be crushed and broken if the workers walk on it before the slab is poured. ▪ Heat recovery ventilators. The additional ductwork and expense of installing an HRV for each unit was beyond the scope of the budget. Instead, common bathroom exhaust fans were used to provide continuous ventilation for each unit. ▪ Energy Star-qualified bathroom exhaust fans, with boost capability. These exhaust fans can be set to run continually at a lower CFM to satisfy the requirements for whole-house ventilation (35 CFM for two-bedroom units, 55 CFM for fourbedroom units) and can boost to 80 CFM for spot ventilation. However, this measure would have cost an extra $135 per fan for 432 fans, or over $58,000. This was beyond the scope of the budget. Measured Performance Monthly gas use data are available for each building, and electric use data are available for each of the 120 apartments. Natural gas is used only for the furnaces serving each apartment, but it is billed at the building level. Everything else is electric. There is one meter for each apartment and two meters covering the common area in each of the five buildings.
SWA
The Energy Information Agency regularly publishes Residential their rated capacity. The contractors reduced the flows, thereby Energy Consumption Survey (RECS) data. In 2005, these data show minimizing the energy loss associated with exhausting an exthat average energy use for all residential buildings in New York State, cess of ventilation air. Field testing by the HERS raters to verify including single-family and multifamily buildings, was 60,000 Btu kitchen exhaust, bath exhaust, duct leakage, and unit tightness per square foot per year. For multifamily buildings in the United States helped the contractors to identify problems and address them. Scheduling inspections and coordinating with all the trades with five or more two-bedroom apartments, the RECS data show average energy use of 62,000 Btu per square foot per year. Though is a challenge with multifamily buildings. For example, insulathe findings cannot be directly compared with the RECS data, SWA tion was moved in order to install a sprinkler system after the found average energy consumption of 40,000 Btu per square foot per insulation was inspected. Obviously, the insulation inspection year for the apartments in the building with two-bedroom units, and should have been done after the sprinklers were installed, but average energy consumption of 37,000 Btu per square foot per year for with dynamic schedules, this can be difficult to coordinate, and both jobs must be done bethe apartments in the buildings with fore the drywall is installed. The four-bedroom units. use of electric-resistance heaters To calculate energy cost savis questionable, given the ineffiings for the NYSERDA program, ciency of the source of electricity. the electric-resistance unit heaters However, the additional cost and in the entryways (four per buildcomplexity of running gas lines ing) were assumed to operate at for these small vestibule heaters 3 kW for 9 hours per day for 120 made gas an ineffective alternadays (that’s the lowest setting, and tive. Stairwell lighting was inithe thermostats were set to 55°F). A tight build-out schedule was kept by setting panelized walls on tially in excess of lighting allowThis was just an estimate; bills insulated slabs. ances, especially since there are show that they are actually operating much less. Lights in the stairway were assumed to operate windows in the stairwells. Photosensors and motion sensors 24/7 and lights in the corridors were assumed to operate for 18 were evaluated, but ultimately the fixtures were modified to hours per day, since they have motion sensors. Again, the bills use one lamp, rather than two, effectively reducing lighting are showing that the common-area lights are operating much consumption by 50%. While spray foam would otherwise have been a good choice less—9 hours per day rather than the predicted 18. The electricresistance heaters also operated much less than we expected—3 for the exterior walls, the challenge of building multifamily housing is the interconnectedness between apartments. The or 4 hours per day rather than 9. Figures 1 and 2 (p. 33) show actual annual gas and electricity builders realized that a flash-and-batt system would probably use for the University Village buildings compared to modeled, have been cost-effective, since they spent so much time air sealor predicted, energy use during one year. REM/Rate was in the ing. A flash-and-batt system would work well as long as the inright ballpark for heating and cooling consumption (in reality, stallers paid close attention to connections from apartment to occupants tend to use a bit more energy here than was predicted apartment, with particular emphasis on duct sealing and leakage to shared mechanical closets. by the model). The project team made a late decision to pursue LEED Gold cerFigure 3 shows average daily apartment electricity use by month. There is a surge in consumption in the heating season. tification. Despite some hang-ups with ventilation and air sealing, SWA attributes this surge to the air handlers. Also, since our the project team was able to achieve LEED Gold on a tight schedutility bill analysis assumes constant occupancy year-round, ule because the architect and the general contractor remained and many of the apartments are vacant in the summer, some of in close communication and because they were both willing to the extra winter electricity use may actually be going for base- learn a new program. On-site training provided by NGBC was also load and not for heating. Common-area electricity consump- crucial. It enabled the trades to work in an integrated way, and it tion was definitely overestimated (see Figure 4). helped them to understand what they needed to do to maximize whole-building performance. Lessons Learned >> For more information: As is often the case with multifamKarla Donnelly is a LEED AP Homes and To learn more about Steven Winter ily projects, air sealing and ventilation LEED Green Rater working in SWA’s residenAssociates, go to www.swinter.com. proved challenging at first. A redesign tial programs. Jim Gunshinan is the editor Contact Karla Donnelly at kdonnelly@ for continuous bath exhaust to meet of Home Energy. Gayathri Vijayakumar is swinter.com and Gayathri Vijayakumar at ASHRAE 62.2 originally led to overvena mechanical engineer performing [email protected]. tilation when fans performed beyond tial energy analysis for SWA. 36
Home Energy
|
M ar c h / A pr il 2 0 1 1
