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Challenge 2K House Section Detail

Infiltration & Exfiltration

Challenge 2000 House cross-section detail

A well weatherized home has a few cracks and leaks as possible. The better a house is sealed, the less infiltration (air coming from the outside) and exfiltration (air flowing from inside to outside) occur. The average home has leaks equal to a hole in its wall 14" square!

To maintain healthful ventilation, the air in your house needs to change only about once every two hours. Typically, air changes occur at twice trhat rate; in severe weather and windy conditions, they happen as many as nine or ten times in a hour. To keep the heated and cooled air you're paying for where it belong -- in your house -- seal up the thermal envelope of your home.

Insulating means lining the envelope of your house -- walls, ceilings, floors -- with materials that don't readily allow heat to pass through. This will keep heat in during the winder and out during the summer.

The effectiveness of insulation materials is measured in "R-values." The higher the R-value the better the insulation.


House wraps, like Tyvek, allow for movement of moisture-not air- and can reduce infiltration by one third.


Loss of heat through infiltration accounts for 40-50% of your total space conditioning costs. Leaky ductwork in attic or crawl spaces alone can account for 25% of every dollar you spend.


Sealing up the leaks in ducts with mastic and insulating with R-6 duct wrap can cut the energy you use to heat and cool your house by 25% reducing the amount of nitrous oxide and sulfur dioxide released in to the enviornment.


You may not be aware of it, but air leaking from ductwork around plumbing, chimneys, vents, light switched, windows and doors can allow one to two housefuls of air to escape every hour. When you're paying to heat or cool that air, air changes can be costly and wasteful.

Weathering your house -- sealing up the cracks, insulating the surfaces -- can reduce the kind of inefficiencies that cost you a lot of money, have serious environmental consequences, and make your homeless comfortable.


Insulating your attic to R-30 can save you up to 30% of your energy bill.


Incorrectly installed insulation- where gaps and holes occur - can cut its effectiveness, and your cost savings, in half.


Ozone-depleting CFCs (chlorofluorocarbons) found in some foam sealants can take 8-12 years to reach the ozone layer. Buy only CFC-free insulating products. For more information about insulation visit the Department of Energy's web site.