By Mark Vanderhoff

Cold floors. Chilly drafts. High utility bills.
These are a few of the unfortunate side effects winter can have on homes, and on the comfort of those who dwell inside them. There is a way to combat these symptoms: creating an air-tight house.

No heat escapes the air-tight house and no cold air infiltrates. To achieve this ideal, we must understand a few natural forces, and then use some tools and tactics to control them.

One of these natural forces has to do with air's incessant desire to be the same pressure everywhere. If the air pressure inside is greater than the air pressure outside, heated air will be pushed out through holes in the building' envelope, or exterior shell. Under the reverse circumstances, cold air gets sucked into the home.

Green building uses the air-tight principle to address this problem in many ways. First of all, any leaks around doors, windows or elsewhere are sealed. Ducts for the heating and ventilation system must also be sealed, however, or they will create the air pressure problems that exacerbate the leaks in the first place.

Another natural force, called conduction, describes heat loss. Everyone knows that hot air rises, but heat can also move up, down or sideways. Conduction is the process by which heat moves through materials.
Insulation stops conduction, or the loss of heat. Some foam insulations also stop the movement of air, which addresses air pressure problems and conduction's relative – convection.

Convection, the process by which heat moves through the air by circulating currents, explains why hot air rises. Conversely, cool air falls. Sometimes, a draft can be caused when air against an old, single-paned window cools, becomes heavy, and then moves down a wall and across a room. Double- and triple-paned windows can help prevent these types of drafts.

With all these different types of heat and air movement, creating an air-tight house involves more than plugging a few holes. Experts often call the whole process “sealing a building's envelope.”

Existing homes can benefit from the same strategies as new homes. Many companies now specialize in detecting leaks in the building envelope using thermal imaging that literally reveals where heat escapes and cold infiltrates. Armed with these images, homeowners can target each area that needs attention.

Of course, a perfectly air-tight house could also be a “stale” house, with air that gets circulated over and over. Old construction methods created houses that were so leaky, outside air flowed in with no problem. Unfortunately, the tradeoff for fresh air was energy inefficiency, cold floors and chilly drafts.
Bring in fresh air with a controlled method solves this problem. Fresh air vents can be linked to the heating, ventilation and air-conditioning (HVAC) system with no leaks. The result provides not only energy efficiency, but healthy indoor air quality.

With an air-tight house, a homeowner might never need to bundle up indoors again.

For more information call the WNC Green Building Council Hotline at 828-254-1995, email us at info@wncgbc.org or visit the resources on our website at www.wncgbc.org