Air Leaks: How They Rot Houses and Waste Energy
One third of the energy you buy probably leaks through holes in your house.
Synopsis: When it comes to conserving energy in your home, one of the best things you can do is identify and seal air leaks. In this article, building-science specialist John Straube outlines the various ways in which a house can leak conditioned air, wasting resources and ultimately your money. Wind pushes drafts through a leaky house, a definite problem in the cold winter months. The stack effect can be problematic in both summer and winter. In winter, rising warm air leaks through the roof and is replaced by cold air sucked in through the bottom floor. In summer, warm air is pulled in through the roof while cool conditioned air is forced out of lower floors. In a house, mechanicals also contribute. Devices such as gas fireplaces, dryers, furnaces, water heaters, range hoods, and bath fans remove conditioned air. The best solution is to build tight and ventilate right.
Stopping air is the second-most-important job of a building enclosure. Next to rain, air leaks through walls, roofs, and floors can have the most damaging effect on the durability of a house. Uncontrolled airflow through the shell not only carries moisture into framing cavities, causing mold and rot, but it also can account for a huge portion of a home’s energy use and can cause indoor-air-quality problems.
A tight house is better than a leaky house, with a caveat: A tight house without a ventilation system is just as bad as a leaky house with no ventilation system — maybe worse. Energy efficiency requires a tight shell; good indoor-air quality requires fresh outdoor air. Ideally, the fresh air should come not from random accidental leaks of unknown size and quantity, but from a known source at a known rate. For this to happen, the house needs an adequate air barrier…