Make your Home Comfortably Efficient
Updated: Apr 23
As a trained Building Science Professional and Home Inspector I see a lot of homes and most have the same problems...
Air Sealing and Insulation; What every homeowner really needs to know.
Insulation on its own is generally poorly used and greatly misunderstood. There is another equally important component that must go right along with it, Air Sealing. No matter what insulation you use, it does much less good if you don’t control the air that can blow right around or through it.
One of the most important things to understand is the principle of “Stack Effect”, whereas your whole house is really a big chimney stack, just like in a fireplace, heat and fumes rise up and out. Starting with your living space, where you try to keep your heat, the heat rises and creates a pressure on the ceiling, pushing to get out, and a pulling pressure on the floor to suck in. Comparatively the air pressure on side walls is somewhat neutral. So, the top and bottom of your home are of foremost importance to control.
Stack effect can make your house feel drafty and cause your home to lose a lot of heat. Cold air is pulled mostly up through your basement from air leaks in every little hole to the outside that it can find. The Rim Joist is usually a big source, ever notice all those cobwebs down there, the spiders know where the wind is blowing in; they hang out near all those holes to catch bugs.
Back up at the ceiling, while it’s good to have a well-sealed attic hatch and no visible holes on your ceiling, but this does not complete the building envelope by any means. Have you ever noticed that your roof doesn’t have snow on it, when your neighbor’s house does, that’s because the heat from your living space is going right out the top of your house? Most homes have a great deal of holes and passageways in the walls from bottom to top that you can’t easily see; plumbing and wiring holes, kitchen soffit boxes, top and bottom of your walls, fireplace chase ways, porch additions, garage gables and those can lights that you love so much, all can be avenues of huge air movement, allowing the Stack Effect to push your heat up out into the attic to warm the roof and neighborhood!
Did you catch the word “envelope’, think of your house like one big sealed envelope, that’s what you want? Sealed as tight as you can get it, then your insulation will work. Yes, you read that right, as tight as possible. An energy auditor may talk in terms of the air sealing and thermal boundaries being complete and aligned, air sealing is the most important thing to have correct in a home. Think if your house was a perfectly sealed and insulated box like an ice cooler. And better yet if it had a bunch of perfect boxes packed inside so you could control every space how you want without drafts?
Don’t ever let someone tell you “you don’t want your house too tight”, and don’t let them tell you that you can control all that moisture running down the inside of your windows and the polluted air your breathing with a loose house or a timed bath fan. You may also be told that your attic needs more ventilation to stop the mold, well it could, but maybe not so much if your Stack effect is under control, like if your cooler was sitting outside and the top was closed tight. Attic ventilation is good but too much can actually cause problems. Excess attic moisture is caused by the pushing air that is carrying moisture and getting past your improperly tightened ceiling; water molecules are smaller than air. We produce a lot of moisture and pollution from breathing, sweating, cooking, house plants, animals, and coming up from that wet floor in the un-controlled basement areas.
Every house that is properly air sealed must be mechanically ventilated to remove the moisture and pollution, but you need to keep your heat, you’re spending a lot of money to make it. An Energy Recovery Ventilator is a basic requirement that will expel these and bring in fresh-filtered, pre-heated air that will improve your interior air quality and health.
And Yes, you also need a correctly sized and controlled bath fan, and it should run for 20 minutes after your shower to evacuate that heavy moisture source. You also must have a proper range hood with the right amount of flow to get the heavy cooking fumes to the outside and not in your face (as in a recirculating, non-vented type).
A bit about fiberglass: when fit correctly and properly air sealed, it can be somewhat effective, and it is cheap. What is not good about the stuff is that Air blows right through it, (no matter how well fit) carrying moisture that can become trapped in it, thus promoting mold growth in the wood around it. The Pink and Fluffy also irritates your skin and arrests your lungs causing respiratory issues (lots of tiny glass shards floating in the air). Finally, mice and vermin love to live in fiberglass and will usually always get into it and destroy its effectiveness, all while using it for their toilet.
Okay, now spend your money in a smart way by properly air sealing along with your insulation. Start at the top, that’s right, stop the air and heat movement from going out the lid; Winter control is obvious but Summer is equally important, the heat from outside is radiating down to cook you and the moisture leakage from below is contributing to mold growth in the attic.
Get all the nasty crushed mouse infested Fiberglass out and to the dump. Air seal all those avenues of air leakage properly. Physically block off all the big holes with plywood, metal or sheet rock. Spray foam at least three inches of hi density closed cell over your attic floor. Add cellulose or “Roxsul” to R-60. Attic venting should equal 1 square foot of net free vent area per 300 square feet of attic floor (Ridge and Soffit vents). Another method and probably better, that is used now days in new construction, is to seal the underside of your roof and soffit area down to the top of walls with High Density (closed cell) Spray Foam.
Basement; Fix the standing (or running) water problems. Seal up the floor or dirt with a good heavy-duty vapor barrier. Seal up every hole from outside and up through the floor, like the giant one around your bath tub plumbing, and properly seal/insulate the Rim Joist, also with High Density Spray Foam. Oh, yes and Don’t ever open your basement windows in upstate NY; summer humidity will introduce more moisture than you think your trying to ventilate out, yes you heard that right!
The last thing is to stuff your walls, if there is nothing in them of course. Note that most new builders pay too much attention to spray foaming walls and then defeat the whole system by just putting Fiberglass in the ceiling and not giving the basement or attic proper attention.
So, get an Energy Audit by a trained BPI certified professional, there are some good ones out there. Pricing and scope of work may vary, so consult more than one before you air seal and insulate your home.
Now when you get your Heat Pumps, you and your home will be perfectly happy!