Green the Orange

Students at Syracuse University experience a Multifamily Performance Program up close and personal.

March 04, 2011
March/April 2011
A version of this article appears in the March/April 2011 issue of Home Energy Magazine.
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Student 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”).

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“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 environmental 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 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.

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 Performance program, go to www.nyserda.org.

The Buildings

The following is a description of Building 1, which has 24 two-bedroom 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 ft2 apartments and four 1,048 ft2 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 on-site with R-21 fiberglass batts, and rim joists were insulated with high-density closed-cell spray foam. Energy Star-qualified vinyl-clad 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-per-hour Energy Star-qualified natural-gas furnace, with an AFUE (annual fuel utilization efficiency) of 92%. Seven-day programmable thermostats are installed in each unit. The domestic hot-water 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 third-floor 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 than buying oversized equipment that is not needed. MERV 8 filters, another LEED for Homes requirement, provide good-quality 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 third-floor 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 fiberglass 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 four-bedroom 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.
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).
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

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.

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.

The Energy Information Agency regularly publishes Residential Energy Consumption Survey (RECS) data. In 2005, these data show that average energy use for all residential buildings in New York State, including single-family and multifamily buildings, was 60,000 Btu per square foot per year. For multifamily buildings in the United States with five or more two-bedroom apartments, the RECS data show average energy use of 62,000 Btu per square foot per year. Though the findings cannot be directly compared with the RECS data, SWA found average energy consumption of 40,000 Btu per square foot per year for the apartments in the building with two-bedroom units, and average energy consumption of 37,000 Btu per square foot per year for the apartments in the buildings with four-bedroom units.

To calculate energy cost savings for the NYSERDA program, the electric-resistance unit heaters in the entryways (four per building) were assumed to operate at 3 kW for 9 hours per day for 120 days (that’s the lowest setting, and the thermostats were set to 55°F). This was just an estimate; bills show that they are actually operating much less. Lights in the stairway were assumed to operate 24/7 and lights in the corridors were assumed to operate for 18 hours per day, since they have motion sensors. Again, the bills are showing that the common-area lights are operating much less—9 hours per day rather than the predicted 18. The electric-resistance heaters also operated much less than we expected—3 or 4 hours per day rather than 9.

Figures 1 and 2 show actual annual gas and electricity use for the University Village buildings compared to modeled, or predicted, energy use during one year. REM/Rate was in the right ballpark for heating and cooling consumption (in reality, occupants tend to use a bit more energy here than was predicted by the model).

Figure 3 shows average daily apartment electricity use by month. There is a surge in consumption in the heating season. SWA attributes this surge to the air handlers. Also, since our utility bill analysis assumes constant occupancy year-round, and many of the apartments are vacant in the summer, some of the extra winter electricity use may actually be going for baseload and not for heating. Common-area electricity consumption was definitely overestimated (see Figure 4).

Total Apartment Daily Electrical Usage
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.

Common Area Daily Electrical Usage

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.

Lessons Learned

As is often the case with multifamily projects, air sealing and ventilation proved challenging at first. A redesign for continuous bath exhaust to meet ASHRAE 62.2 originally led to overventilation when fans performed beyond their rated capacity. The contractors reduced the flows, thereby minimizing the energy loss associated with exhausting an excess of ventilation air. Field testing by the HERS raters to verify kitchen exhaust, bath exhaust, duct leakage, and unit tightness helped the contractors to identify problems and address them.

 Scheduling inspections and coordinating with all the trades is a challenge with multifamily buildings. For example, insulation was moved in order to install a sprinkler system after the insulation was inspected. Obviously, the insulation inspection should have been done after the sprinklers were installed, but with dynamic schedules, this can be difficult to coordinate, and both jobs must be done before the drywall is installed. The use of electric-resistance heaters is questionable, given the inefficiency of the source of electricity. However, the additional cost and complexity of running gas lines for these small vestibule heaters made gas an ineffective alternative. Stairwell lighting was initially in excess of lighting allowances, especially since there are windows in the stairwells. Photosensors and motion sensors were evaluated, but ultimately the fixtures were modified to use one lamp, rather than two, effectively reducing lighting consumption by 50%.

While spray foam would otherwise have been a good choice for the exterior walls, the challenge of building multifamily housing is the interconnectedness between apartments. The builders realized that a flash-and-batt system would probably have been cost-effective, since they spent so much time air sealing. A flash-and-batt system would work well as long as the installers paid close attention to connections from apartment to apartment, with particular emphasis on duct sealing and leakage to shared mechanical closets.

The project team made a late decision to pursue LEED Gold certification. Despite some hang-ups with ventilation and air sealing, the project team was able to achieve LEED Gold on a tight schedule because the architect and the general contractor remained in close communication and because they were both willing to learn a new program. On-site training provided by NGBC was also crucial. It enabled the trades to work in an integrated way, and it helped them to understand what they needed to do to maximize whole-building performance.


Karla Donnelly is a LEED AP Homes and LEED Green Rater working in SWA’s residential programs. Jim Gunshinan is the editor of Home Energy. Gayathri Vijayakumar is a mechanical engineer performing residential energy analysis for SWA.

 

For more information:

To learn more about Steven Winter Associates, go to www.swinter.com.
Contact Karla Donnelly at kdonnelly@swinter.com and Gayathri Vijayakumar at gvijayakumar@swinter.com.

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