09/20/2011

www.gupta-verlag.de/polyurethanes

A study in sustainable living - SPF lays the foundation for a cutting-edge, sustainable home

[image_0]Cleantech's showcase home (fig. 1) uses the most sustainable products currently available. It was designed not with disparate sustainable components, but using a systems approach, ensuring that sustainable elements work together. The home features geothermal energy, solar photovoltaic panels, solar thermal hot water, and sustainable materials throughout. Each of the sustainable products contributes to the home's current evaluation for a LEED Platinum rating, 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 air tight home, minimising heating and cooling cost from air infiltration, which leads to significant energy losses,” said James Farnham, President, Cleantech. 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 minimizsed in an economical fashion. Energy efficiency starts with the building enclosure. The building enclosure
Cleantech recognised that closed cell SPF was the best insulation for creating a tight building envelope, and chose Certain­Teed's CertaSpray foam insulation, which is based on technology from Huntsman Polyurethanes. Cleantech chose Certa­Spray SPF for its exceptional R-values and reputation for performance, as well as for the structural qualities, moisture vapour retarder and air barrier that closed cell foam provides. Much more than just insulation, SPF offers improved building durability, healthy indoor air quality and enhanced moisture management - all critical factors in building quality homes. [image_1_right]CertaSpray's closed cell foam insulation was applied in the wall cavities (fig. 2), 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 was the reduced lumber usage that closed cell SPF enabled. Use of SPF allowed the construction company to use 2 x 4 inch framing, while still achieving its targeted high R-value. In addition to reducing lumber usage and costs, 2 x 4 inch framing helped to save on window and door extension jambs and provided additional square footage. Air tightness and indoor air quality
Air tightness was a significant factor in reaching the energy efficiency goals. The home's air tightness was officially rated to be much better than typical construction (fig. 3). SPF creates an excellent air barrier system, positively impacting energy efficiency, reducing condensation potential, and can improve air quality in the form of reduced allergens, pollutants, and noise. [image_2]A blower door test found an air infiltration rate of ~ 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 minimising infiltration of unconditioned air. Although the home is tightly constructed, the indoor air quality of the finished home is excellent, with balanced ventilation provided through heat recovery ventilators (HRVs), passing through a filter before entering the home. This allows control of the air exchange with the outside rather than allowing unknown amounts of outside air to enter the home carrying allergens, moisture and noise. The HRVs recover energy from the exhausted air to provide this controlled air exchange in an energy efficient manner. Rightsizing heating & cooling systems
SPF significantly reduces infiltration of unconditioned air, allowing the heating and cooling design loads of this home to be significantly smaller than normal for HVAC equipment used in the surrounding area. 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. SPF provided valuable points in several areas for Cleantech's pursuit of LEED Platinum certification for this home: High quality insulation Air tightness, 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 2 x 4 inch 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 and SchoolsSM certified and meets the testing requirements to get credit for a low emitting material. Lastly, it can also contribute to protection from garage pollutants for credit in the environmental quality category. Conclusion
Cleantech created a truly cutting-edge home in terms of sustainability. In fact, the official building rater suggested that this home will use 60 - 70 % less energy than a home built to existing code standards. The home is currently being used as a teaching centre to showcase sustainable building techniques and design, as well as new products and construction materials used in high-performance homes.

www.gupta-verlag.de/polyurethanes