The Thermal Envelope
- Have a very low rate of random infiltration of outside air by building a tight structure.
- Make sure all HVAC ductwork and the air handling unit is located within conditioned space.
2x4 walls get about 3" of insulation for an R value of 11. For more information on R value and the insulation effectiveness see graph below.
About 5" of Icynene is applied directly to the underside of the roof deck. No other insulation will go in the ceiling.
How It's Done
The only way to properly control the temperature and humidity levels of inside air is to build a tight enough structure to eliminate random air exchange with the outside. Icynene performs this role beautifully. It fills cavities of any shape or size and bonds with all building materials to create a continuous air barrier around the entire home. The amount of air leakage for the envelope of a typical Icynene home, as measured by a blower door apparatus, is .1ACHnat or Air Changes per Hour at natural pressure.
Since most ductwork is located in the attic, we apply the Icynene insulation directly to the underside of the roof deck, creating a completely sealed, unvented, semi-conditioned attic space. Moving the thermal envelope boundary from the ceiling to the underside of the roof deck to bring the ductwork into conditioned space is a fundamental part of this system.
As this graph shows, just 3" of Icynene controls over 90% of total heat flow.