Whenever I see an older home being remodeled, especially if it’s an extensive renovation, I always wonder if the homeowners and the contractor know what a great opportunity they have to make the house tighter. Whether they’re opening up walls or adding new ones, working in the attic, the basement, or the crawl space, air-sealing should be part of the scope of work.
Here are a bunch of reasons why:
1. Keep conditioned air inside. Air leaks waste energy. If you’re spending money on air conditioning or heating your home, why would you want to make it easy for that expensive air to escape?
2. Keep unconditioned air outside. Air leakage works both ways. When a cubic foot of conditioned air goes outside, it must be replaced with a cubic foot of unconditioned air coming inside. That adds to the heating or cooling load of your home and costs you money.
3. Keep bad air out, and stay healthy. Not only is the air leaking in costing you money, it’s probably not the most healthful air either – moldy air from the crawl space, carbon monoxide and gasoline fumes from the garage, dead animal parts from the attic, pollen from outdoors… You get the idea.
4. Keep moisture out of your walls. When it’s hot and muggy outside, you don’t want to pull that moisture into your building cavities and start biology experiments. When it’s cold outside, the warm, relatively humid air inside can condense inside wall cavities and rot them out.
5. Sheathing in older homes can be very leaky. For the past 60 years or so, builders have used sheet goods (plywood & oriented strand board mainly) for wall sheathing and subfloors. Before that, homes had diagonal 1-by lumber (photo above). There’s a lot more air leakage through the gaps between all those boards than newer, plywood-sheathed homes have. Other types of sheathing can be very leaky, too. The Celotex I found in my condo bathroom remodel had lots of air leakage pathways. Same goes for floors. Seal ’em up! Once you close up those walls, you’ve missed your chance.
6. Window and door openings are major air leakage sites in walls. Whether you replace windows and doors or not, you may well have access to the gaps between the window or door frame and the wall framing. Use an air barrier material (not fiberglass or cellulose!) to fill those gaps.
7. Those walls, floors, and ceilings may not have been open for decades, and when you’re done, they’ll be closed up for decades again. Don’t miss this opportunity. If you’re already in there doing remodeling work, take full advantage. You’ll be rewarded with a house that’s more comfortable, durable, healthful, and efficient if you do it properly.
There you have it. And if you’re still worried about that old myth that you shouldn’t make your house too tight, well, don’t. A house does NOT need to breathe; people do.
Allison A. Bailes III, PhD is a speaker, writer, building science consultant, and the founder of Energy Vanguard in Decatur, Georgia. He has a doctorate in physics and is the author of a popular book on building science. He also writes the Energy Vanguard Blog. You can follow him on Twitter at @EnergyVanguard.
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