This was written by Tim Snyder of Dr. Energy Saver.
It’s wintertime. If you can feel cold drafts coming into your house, it’s a sure bet there’s heat energy going out. Sealing air leaks in key areas will cut cold drafts and your heating bill.
Here in New England, the arrival of cold weather inevitably triggers concerns about the cost of staying warm. Because we have so much rocky terrain and so many rural communities, low-priced natural gas isn’t available as a heating fuel in many areas. As a result, we watch the price of fuel oil carefully, while doing what we can to cut the cost of staying warm.
Insulation is the first thing most of us think about when it comes to keeping a house warm in the wintertime. But the fiber-based insulation used in many attics –fiberglass batts, loose-fill fiberglass and cellulose insulation—can’t stop convective heat loss that occurs as “conditioned” (warm) air leaks out of your living space. Tiny air leaks throughout your house create a convective air movement pattern that building scientists call the “Stack Effect.” As the warmest air rises naturally to the top of your living space and leaks into the attic, a resulting vacuum effect draws cold outside air into the house through leaks in lower sections. To short-circuit the Stack Effect, you have to stop as much leakage as possible –especially leakage into the attic. Properly air sealing the following “target” areas can substantially reduce energy-wasting air leaks. In fact, air sealing combined with proper levels of insulation can cut your heating and cooling costs by 20%.
4 ways to short-circuit the Stack Effect and save energy
- Seal leaks in and around the fireplace. Warm interior air can easily leak out the fireplace chimney, even when the damper is closed. If you use your fireplace frequently, have airtight glass doors installed so that you can close this major leak when you’re not enjoying the fire. If you don’t use your fireplace, consider closing off the chimney with an inflatable bladder. Available from Amazon and other sources, these “draftstopper” bladders seal air leaks much more effectively than the fireplace damper can. Another major air leak area can be found where your wallboard meets the masonry of the fireplace and chimney. Use “fireblock-grade” spray foam to seal the gap between these surfaces and you’ll be eliminating some major leakage.
- Insulate and seal the attic access hatch or drop-down stair. A typical house will provide attic access with a hatch (aka scuttle) or a drop-down stair. Either way, these access points represent an Achilles heel in your home’s “building envelope;” they leak air and provide very little insulation from frigid attic temperatures. Readymade scuttle and hatch covers from different suppliers (such as Battic Door: http://www.batticdoor.com/) are easy to install and help to seal and insulate this weak spot.
- Stop energy leaks around recessed “can” lights. Are there recessed lights installed in the ceiling that separates your living space from the attic? If so, every hole cut in the ceiling to install these lights is an energy drain. Some homeowners close up these holes and replace can lights with surface-mount light fixtures. A less-expensive solution is to go into the attic and install specially designed airtight covers over the cans and wiring that are exposed in the attic. Sealing the cover to the drywall and then adding insulation over the cover is a very effective corrective strategy. A full-service insulation contractor should be able to do this work as part of an attic insulation upgrade, which is also a smart idea.
- Seal around electrical outlets in exterior walls. The first three sealing tasks are primarily for limiting air exfiltration –conditioned air leaking out of your living space. Step 4 will help to cut down on air infiltration –cold exterior air that leaks into exterior wall cavities and then into your living space. Home centers sell air sealing foam gaskets designed to be installed beneath the outlet cover plate. These gaskets are inexpensive and effective. But before installing one, use all-purpose caulk or low-expanding spray foam to seal any gaps between the drywall and the electrical box for double protection against cold drafts.
It would be irresponsible to discuss air-sealing a house without mentioning the benefits of a blower door test, which is always performed as part of a home energy audit. To perform the test, a powerful, specially calibrated fan is mounted in an airtight housing that’s tightly fit in an exterior doorway. After technicians make sure the house is in “winter” mode (windows and exterior doors closed, fireplace dampers closed, etc.), the fan is turned on to suck air out of the house. With the fan operating, the energy analyst can accurately measure the total amount of air leaking into the house. Your air leakage rate is compared to the benchmark rate for a “tighter,” more-efficient house of the same size. The blower door test gives you a tighter air leakage rate to aim for with air-sealing work. During the test, the technician can go around the house and show you where your major leakage is occurring –exactly the information you need to seal leaks and save energy.
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