A Study in Sustainable Living
Spray Polyurethane Foam Lays the Foundation for a Cutting-edge, Sustainable Home
When Cleantech, a green residential development and consulting company, began conceiving a sustainable showcase home, its top priority was to reduce energy usage in both a sustainable and aesthetically pleasing fashion. Cleantech built a strong foundation for sustainability by first designing a building enclosure that would stand up to the heating demands in New England.
Cleantech’s showcase home boasts the most cutting-edge sustainable products currently available. It was designed not with disparate components, but with a systems approach, ensuring that elements work together. This home features geothermal energy, solar photovoltaic panels, solar thermal hot water and sustainable materials throughout.
Many products contributed to the home’s LEED® Platinum rating application, but the home’s building enclosure laid the foundation for achieving a high level of energy efficiency. “A closed cell spray polyurethane foam (SPF) thermal and air barrier system created an airtight home that minimizes the air infiltration that can lead to significant energy losses,” said Cleantech president James Farnham. Cleantech understood that the cutting-edge technologies employed to provide energy to the home only made sense once the energy load on the home was minimized in an economical fashion. Energy efficiency starts with the building enclosure.
THE BUILDING ENCLOSURE
Cleantech knew closed cell SPF was the best insulation for creating a tight building envelope, and chose CertainTeed’s CertaSpray® Closed Cell Spray Polyurethane Foam. Cleantech chose CertaSpray not just for its exceptional R-Values and reputation for performance, but also for SPF’s structural qualities and superior performance as a moisture vapor retarder and air barrier. Much more than just insulation, CertaSpray offers improved building durability, helps maintain healthy indoor air quality and provides moisture management – all critical factors in building quality homes.
CertaSpray was applied in the wall cavities, to the underside of the roof deck, on basement walls and in frame floors over the garage and porch to protect the home against heat, cold, air infiltration, moisture and sound.
An additional benefit of using SPF was that Cleantech was able to utilize 2X4 framing and still achieve its targeted high R-Value. In addition to reducing lumber usage and costs, 2X4 framing helped Cleantech save on window and door extension jambs and provided additional square footage.
AIRTIGHTNESS AND INDOOR AIR QUALITY
Airtightness was a significant factor in reaching the energy efficiency goals. Ted Staples, a certified HERS rater from Reclaimed Energy, found the home’s airtightness to be much better than typical construction. SPF helps create an excellent air barrier system, positively impacting energy efficiency, reducing condensation potential and helping to maintain indoor environmental air quality by reducing infiltration of allergens, pollutants and noise.
A blower door test found an air infiltration rate of approximately 0.07 NACH (natural air changes per hour), meaning roughly 7% of the home’s air volume is replaced hourly via air infiltration. A typical home built in 2002 - 2003 has roughly 55% of its air volume replaced hourly with unconditioned outside air. Each cubic foot of air that enters via infiltration must be heated/cooled to get the house back to its thermostat set point. Thus, SPF has a very significant impact on energy efficiency by minimizing infiltration of unconditioned air.
Although the home is tightly constructed, the indoor air quality of the Cleantech home is excellent, with balanced ventilation provided through heat recovery ventilators (HRVs) passing through a filter before entering the home. This system allows control of the air exchange with the outside rather than allowing unknown amounts of outside air to enter the home carrying along allergens, moisture and noise. The HRVs recover energy from the exhausted air to provide this controlled air exchange in an energy-efficient manner.
RIGHT-SIZING HEATING AND COOLING SYSTEMS
Because SPF significantly reduces infiltration of unconditioned air, the heating and cooling design loads of this home are significantly smaller than the rule of thumb for HVAC equipment in Massachusetts.
ACHIEVING LEED®'S HIGHEST CERTIFICATION
LEED® assigns points based on energy savings, water efficiency, CO2 emissions reduction, improved indoor environmental quality, and stewardship of resources and sensitivity to their impacts. Certaspray contributed to achieving valuable points in several areas for Cleantech’s pursuit of LEED® Platinum certification for this home.
SPF contributes LEED® points in the Energy category in three ways:
• High quality insulation
• Airtightness, typically 0.05 - 0.20 NACH for SPF homes
• Design flexibility to easily accommodate ducts in conditioned space
However, SPF can also contribute in less obvious ways. In the Materials and Resource category, closed cell SPF can assist in achieving points for material efficient framing. Not only did the high R-Value of closed cell SPF allow the use of 2X4 stud members, the structural properties of the foam increase racking strength and facilitate use of wider structural member spacing. CertaSpray® closed cell foam is also GREENGUARD® Children & Schools certified and meets the testing requirements to get credit as a low-emitting material. Lastly, it can contribute to protection from garage pollutants for credit in the Environmental Quality category.
Cleantech’s home is truly a cutting-edge structure when it comes to sustainability. In fact, the HERS rater found that this home will use 60 to 70% less energy than a home built to code. The home is currently being utilized as a teaching center that showcases sustainable building techniques and design, as well as new products and construction materials used in high-performance homes.
LEED® is a registered trademark of U.S. Green Building Council (USGBC).