Biggest Sources of Heat Loss in Your Home
Understanding Heat Loss
Heat loss in a home occurs in places where poor insulation exists, or where air leakage occurs. In either case, heat and cold air will transfer through the points of least resistance. Contrary to popular thinking, heat does not move solely upward. Heat can move in any direction - up, down, sideways, diagonally, and so forth - it will move in the path of least resistance. In this case, hot moves to cold as the two try to equalize.
For example, it is 30 degrees F outside and your home is heated at 65F. If your walls are uninsulated and your attic is insulated, heat will move through the walls to the outside as it tries to equalize with the exterior cold air. Since the exterior air volume far exceeds the interior air volume, the result is a freezing house. If both your attic and walls are uninsulated, and you have a leaky basement, heat moves out in every direction! Understanding this basic concept is vital to understanding the overall heat loss occurring within your home.
What about windows and doors?
Windows and doors are, again contrary to common belief, the least amount of heat loss in the home. Imagine the surface area of a wall in your house. Then consider what percentage of that wall is taken up by windows. Do this for the entire exterior of your home. Generally, the overall percentage of fenestrations (windows and doors) is small compared to the entire surface area.
It is certainly true if you have a very old home with windows that rattle every time the wind blows, or have holes large enough to feel gusts of air coming through - these should certainly be sealed up. But switching from a single pane window to a double pane window is not a major change in the insulation value. This is certainly true for the cost of replacement windows - a typical payback on new windows is something in the range of ten years or more! In general, windows only account for about 10% of your home's heat loss. In comparison, walls and attic account for about 70% of your heat loss.
Points of Heat Loss
Your walls, if they are devoid of any insulation, are a major point of heat loss. But walls are not the only place heat can escape from the home. An uninsulated attic can swiftly deplete heat from a house - and typically these are the easiest places to add insulation to! As a percentage of area exposed to the exterior, an attic usually covers the entire footprint of a house, which is a considerable portion of the overall area. Attics also experience the most air leaks - for example, an uninsulated hatch is like having a window wide open to the outside. In balloon-framed houses, wall tops act like hot air ducts, dumping heat from the living space into the attic. Sealing these leaks can be a major step in improving your heat loss. Of course, adding insulation is also a good idea. Some people suggest R-38, others R-60. The simple fact of the matter is the more the merrier.
Basements and crawl spaces can also leech heat from a home. This is especially the case in very old homes that often have field stone foundations and/or cramped dirt crawlspaces. In many of these spaces - especially inaccessible crawls - the foundation is often not sealed properly to the outside. Either dig away the soil from the outside and repair the foundation, or do the same from the inside. In field stone basements, often the wood footings of the house do not sit squarely on the stone foundation, resulting in numerous little gaps. Using spray foam in a dispenser can is a quick and simple way to fix these little holes.
These three places - attics, walls, and basements/crawlspaces - are the major points of heat loss in any home. By strengthening the insulation in these spaces, and preventing as much air infiltration as possible, this can see a drastic improvement in heating and cooling your home.
