air-sealing BASICS

Look high and low to find and plug air leaks that cost you money and comfort.

-  BY MIKE GUERTIN AND ROBERT SHERWOOD

The Path TO A TIGHTER HOUSE

HOW HOUSES LEAK AIR Warm air rises, creating a zone of higher pressure at the top of a house that forces air out of any hole it can find. This escaping air creates a zone of lower pressure at the bottom of the house that sucks in air through holes and cracks. This is the stack effect. Sealing leaks at the top and bottom of the house is the most effective approach for stopping it. The colder it is outside, the stronger the stack effect, so air-sealing can have a big impact in cold climates (zones 4 to 8) and a lesser one in mixed climates (zone 3)| It is not as important in warm climates (zones 1 and 2).

TOOLS for finding air leaks

SMOKE GENERATOR A handheld smoke stick/puffer fog pencil works like an old Lionel locomotive, generating vapor by heating glycerin. You can buy one online for about $35.

HOMEMADE BLOWER DOOR Some scrap plywood and a $150 fan create a blower door that's adequate for finding air leaks.

three materials for stopping air leaks

1. RTV SILICONE High-temperature RTV silicone sealant can handle temperatures up to 600°F. It's more flexible than fireblock sealant, so it's a good choice for use around chimneys and exhaust ducts. It's available in 3-oz. squeeze tubes and gunnable 10-oz. tubes at hardware stores and online sellers.

2. ACOUSTICAL SEALANT

Meant for soundproofing, acoustical sealant never hardens, and it accommodates the normal movement of building materials without cracking. You might have to go to a commercial drywall supplier to find it.

3.SPRAY FOAM Ranging in price from about $20 to over $100, foam guns make applying spray foam easy. Cans of foam for guns come in several varieties, from minimal-expanding for use around doors and windows to gap-filling for higher-volume applications. It's widely available online and at lumberyards and home centers.