Air Barrier
The Air Barrier System and the Stack Effect;
The next largest energy loss process is convection. Convective heat is heat that moves through air and water (fluids) and it is more noticeable during the winter but occurs all year long. As warm air rises it escapes through leaks in the attic. This creates negative pressure in the building envelope. This pressure sucks air in through windows, doors, and other penetrations in the home. Air sealing the attic goes furthest in stopping these kinds of drafts and leaks. The air barrier of a house is of very high importance for energy efficiency but was seldom addressed by builders.
Fiberglass Insulation is NOT an Air Barrier.
Convected Heat Loss is Addressed by Improvements to a Homes Air Barrier By:
- Attic Air Sealing: This is dirty, dangerous, tedious work that we happily do everyday. An air sealed attic is the first step toward super-insulating your home. Based on a U.S. Department of Energy study, home owners can expect air sealing to lower their space heating consumption around 18 to 30 percent.
- Duct Sealing: Very large efficiency gains can be made by sealing the ductwork and balancing the HVAC loads to each room. Progress Energy Carolinas has found an average of 20% energy loss in duct systems that they studied in North Carolina losses 20%. This is kind of like going to the grocery store and leaving every fifth bag behind! A large and unnecessary loss.
- Crawl Space Air Sealing: Prevents air from being inducted through the crawl space. Helps with odor and insect control also.
- Cellulose Insulation Over Spray: Cellulose is a totally recycled material that outperforms fiberglass attic insulation on nearly every measure.
Here are two PDF files with more information on sealing your attic: