"Hanging duct work is also different. In certain situations, you might nail a hanger to the top chord of a truss, but here you can't because it's going to be covered with foam insulation. But that's the advantage of Icynene. We had to reconfigure how we were going to hang the duct, and take it off of web members of the roof trusses. For example, from the bottom chord of the truss, we built a support of two uprights made from scrap 2x4, and hung the black strap to support the duct work from these two upright pieces."

Technology Highlights

This project included the following PATH-profiled technologies:

• Air admittance valves
• Drywall clips and stops
• Ducts in conditioned space
• In-line exhaust fan
• Low-VOC paints
• Steel framing
• Tubular skylight
• Windows with high-performance glass
• Wood with low-toxicity preservatives

"When you put the A/C in conditioned space in a tightly sealed building, you also have to think about introducing make-up air to compensate for the air expelled by exhaust fans. That air should be introduced from outside through a small duct on the return side. That way it is filtered and either cooled or heated before it gets pumped through the house."

"In our case, since it's a small house, the make-up air duct is 4". It's a totally passive system, so when the HVAC is on, it will pull air into the house. You want to keep a small positive pressure inside the building to keep the pollutants and outside air out. Experts recommend about 4 Pascals of positive pressure in the building at all times."