I: Overview
Insulation is one of your home's first defenses against wasteful energy spending. According to the Department of Energy, 50%-70% of the energy used in the average American home goes toward heating and cooling. That means you've got big (huge!) potential for savings by increasing your home's capacity to keep out either the summer heat or the winter cold, by improving your home's building envelope. The envelope is basically the sum total of everything that shields your home from the elements: paint, siding, framing, insulation, windows, doors, shingles, bricks, etc. Although none of these components can be viewed in total isolation, (an Energy Star certified window won't do you much good if you have string-beads hanging in your front doorway), insulation is an important part of the envelope. Inadequate (or absent) wall, ceiling and floor insulation can lead to massive energy waste.
1. Evaluate your needs. We strongly recommend a home energy audit conducted by a certified professional. A quick look with an infrared camera during an energy audit will reveal the areas where heat is escaping your house, which signifies either an air sealing problem or inadequate insulation.
2. Make sure you are wearing a hat. This you can do on your own. Hot air rises. That means the attic is one of the most important parts of your home in terms of controlling heat loss. A simple way to make sure you are covered: pop your head up into the attic. If you can see floor joists, you need more insulation. If all you see is insulation, check how many inches deep it is. If your attic has a floor, pop up a board and do the same. Multiply that number by 3, and you'll have a very loose approximation of the R-value. An adequate R-value will differ depending on where you live, but should be somewhere between 30 and 60 . If your figure comes up short, you might consider adding insulation. Remember, too, that the insulation should be level and evenly distributed, without any gaps or holes; humps, bumps and low spots can compromise the whole system. And even if you have two feet of of high-quality fiberglass, a couple gaps for air leakage could reduce your R-value a lot, in addition to carrying unwanted moisture up into the attic. So make sure the attic floor is very well sealed before adding any insulation.
Ultimately, your home cannot be energy efficient if your building envelope is continuously leaking energy, and targeted insulation in problem areas can be a good way to prevent that. Whether you choose to hire an energy auditor right off and wind up completely retrofitting your home, or just supplementing the insulation in your attic with a few extra inches of cellulose, you'll be sure to enjoy a more comfortable indoor climate and a more manageable energy bill at the end of every month.
4. Assess the quality of your insulation. A number of things can compromise what would otherwise appear to be adequate R value. Fibreglass batts that are compressed by electrical wires or plumbing, and air leaks that allow flow within the insulation cavity can reduce R values by as much as 50%. Recessed lights in cathedral ceilings may compress insulation, and moisture from leaks or condensation can render r values weak.
Comments
@craigsenglin -- right you are! Hot air rises because it is less dense than cold, and thus is only relevant in a case of convection -- air movement. Heat, being a higher energy state than the lack thereof (which us humans know as "cold") always goes away, this point being made in the laws of thermodynamics, in particular the one known as entropy.
In practical terms, don't just insulate your attic! Heat gets out any way it can. Insulate your walls, floors and basement.
Tom
Posted by Tom Harrison on Jan 10, 2010 6:43pm@craigsenglin -- Many thanks for the comment. You're very right (that was an oversight of mine), I have updated the article to be more accurate and would love to hear any more insights you might have -- keep em comin!
Posted by Will on Jan 12, 2010 5:40am