Winter winds can make your home drafty and drive energy bills through the roof. With energy costs so high, now is a good time to consider weatherizing your home.
Only 20 percent of homes built before 1980 are well insulated. Tightening up your house is the cheapest and most effective ways to reduce energy bills, summer and winter. A tight home also reduces your carbon footprint while making your home considerably more comfortable.
In a typical house, a third of the conditioned air escapes from the ceiling, walls and floor. Because hot air rises, in winter the ceiling is area of greatest concern. If you have an older home, checking the insulation levels in the ceiling and floor is usually fairly straightforward: If you have less than 10 inches of insulation in your ceiling, consider adding more. If you have no insulation in your floor, add it there as well.
Checking exterior walls for insulation takes more ingenuity. Sometimes you can tell by removing a cover plate from a switch and looking through the gap with a flashlight. Because insulating existing walls is more difficult, I recommend insulating the ceilings first, then the floor, and the walls last.
The R value is a measure of resistance to heat flow. Higher R-values increase resistance to heat flow. Ceilings should be insulated to at least R-30, but preferably R-38; walls to R-13; and floors to R-19.
A caveat on R values: They do not take into account the tightness of the seal. Imperceptibly small gaps allow air exchange with the exterior. And different installation methods can make a big difference in the tightness of your home’s envelope.
The Cadillac of insulation is the spray-on foam. This method seals virtually every gap, making the thermal resistance of the wall far better than with any other method. Blown-in insulation works very well at first, but has a tendency to settle and get pushed aside by air flows, reducing its effectiveness over time.
Insulation batts tend to stay in place well, but are subject to small gaps around pipes, electrical lines and other impediments which have a big impact on the tightness of the installation. Careful fitting of the batts makes a big difference.
Make no mistake, all these methods are far and away better than no insulation at all.
What the insulation is made of is almost as important as the method by which it is installed. Fiberglass, the standard until recently, has competition from products that are better in many ways. Some of the products, such as cellulose and recycled cotton, are competitive in price and quality to fiberglass but much more environmentally friendly. Other products, such as the spray-on foams, are of much higher quality than fiberglass but come at a price premium.
Sealing air gaps is another inexpensive way to combat heat loss. Check your doors and window for gaps by looking from the inside out toward daylight. Installing weather stripping will greatly reduce losses.
Wall and ceiling penetrations by exhaust fans, attic doors, electrical boxes, flues and pipes also have a big influence on efficiency. On a windy day, hold an incense stick up to the various penetrations in the walls and ceiling. If the smoke moves horizontally, you have an air leak. Caulking, canned foam, electrical box gaskets and a bit of insulation can seal most of these cracks, reducing heat loss by as much as 20 percent.
If you are building an addition or a new house, the typical insulation and sealing methods used today leave a lot to be desired. But if you hire an architect with knowledge of the latest science on building envelopes, the quality of your final product will be far better.
New methods are now available to evaluate how well a house is insulated and sealed. For example, some tests pressurize your house to find out how quickly the air leaks out. Thermal cameras take pictures of where heat escapes, alerting you to problem areas. These relatively inexpensive tests expose problems in workmanship common to construction.
As everyone knows — at least everyone in a drafty house in the coldest months of winter — a well-sealed house is a wise investment.
