Ultimate Heat Efficient Home Guide: Insulation blanket

An extra blanket of insulation

Focus on filling holes and cracks around your home to save heat (and money)

(Getty Images / Photo Researchers)

(Getty Images / Photo Researchers)

In part one of the Ultimate Heat Efficient Home Guide, we started by making sure the furnace worked efficiently and that our lifestyle wasn’t hindering our home’s efforts to warm us. Now, we need to turn our attention to the more demanding do-it-yourself tasks in order to create a heat efficient home.

Step 1: Fill the gaps (and cracks and holes)

If you’re looking for one task that can significantly improve your home’s overall heat efficiency, then look no further. Eliminating all gaps and cracks has a tremendous impact on your home’s ability to retain the heated air your furnace creates. What does eliminating cracks and gaps actually do? Well, remember the “stack effect”—where hot air rises, seeps out, this air escape creates pressure in your home that creates a vacuum, that sucks cold air in through the cracks in your home. Well, that cold air enters through all the gaps and cracks in your home. Even a small, dime-sized hole in your home will create significant cold air leakage into your home. (Some contractors state that cracks and gaps account for up to 20% of your home’s heat loss.)

So, the first step to creating a seal is to fill all the holes or cracks in your home’s external walls. That means visually inspecting under and over all windows, beside windows and doors, and all transition areas—where brick or siding meets trim and where walls meets soffits and roof lines.

Once you’ve identified the cracks, you’ll want to use caulk to fill them. “Use a latex, rather than a silicone-based caulk, to fill cracks,” explains residential contractor, Mark Pervan. (Note: He’s my hubby!) Latex caulk can be painted to match your home’s exterior colours; silicone caulk cannot be painted. For windows, remember to caulk only on three sides, leaving the bottom to provide an escape for moisture. “The average house will take up to three tubes of caulk to seal all cracks,” says Pervan. For gaps too large for caulking, use spray-foam products. (All this might be hard to do in the winter, so just make a note that come the spring, you need to walk around your home checking and sealing any holes and cracks.)

Step 2: Fill the holes in your attic (they’re bigger than you think)

Most people assume that if you stuff enough insulation into your attic, you’ll eventually reduce heat loss and increase your home’s heat efficiency. This is just not true. “An insulated attic isn’t necessarily a sealed attic,” explains Pervan, who’s had to repair, restore and seal countless roofs over the years. He adds, “insulation is designed to slow down heat loss—as the air has to pass through a solid material. It’s not designed to stop airflow.” Unfortunately, by just paying attention to the insulation, most home owners and up spending good money without actually fixing the problem. “Half the money people pay for insulation is lost due to leaks,” says Pervan. “By sealing the attic floor before insulating, you’ll save a lot more money.”

The problem is your attic acts like a chimney. Hot air rises, enters your attic through gaps and holes in your attic floor, and is then forced out through the vents. This in turn creates pressure in your home that causes cold air to be sucked in through the various cracks and gaps that exist between building materials. To appreciate how much heat is lost—even in well-built and well-insulated homes—check out the Washington Post’s graphic on a home’s average heat loss through everyday gaps and cracks.

So, to increase your home’s heat efficiency, you need to stop letting hot air get into your attic. And you do this by sealing all gaps and cracks in your attic floor. Examples include the tops of light fixtures, holes where pipes and wires enter, the spots where chimney and air ducts enter and exit, as well as the top plates of all interior transitions.

If your attic is already insulated, you’ll need to climb up and roll-back the insulation so you can see the attic floor. However, if you want a quick and (literally) dirty trick for finding leaks in your attic, just climb up and, with a flashlight, start to look for dirty insulation (or gray or black smudges). Wherever you see dirty insulation there will be air passing through—the insulation is actually acting like an unintended air filter. Wherever there is a leak, you’ll need to seal. (If your attic is filled with loose-fill insulation, you may need to call a professional to seal the attic.)

Just like outside, you can use caulk to fill gaps no more than ⅜-inch wide. For holes up to 1-inch wide, use expanding urethane foam. For larger holes, create a custom-plug (using drywall); push it in place and then seal the edges with urethane foam. Another option is to use fiberglass insulation stuffed into garbage bags, but be careful: you don’t want any holes in the bag as wet insulation can lead to mould and even rot (if it’s touching wood). To insulate gaps around chimneys, stove vents or wood-stove flues use a sheet-metal collar and heat-resistant caulk. If you’ve got a hatch or door leading to your attic, make sure you apply weather-stripping around the edges door. For any other intrusions (such as cathedral ceilings or exposed beams) apply caulk where the drywall meets the exposed beams.

Once you’ve sealed the attic, then you can add insulation. “Adding insulation is like adding an extra blanket to the bed,” says Pervan, “it boosts your home’s ability to retain heat.”  If you’re adding more insulation (rather than replacing insulation) then use unfaced batts or loose fill. According to Consumers Report your attic should have 11 inches of fiberglass (ie: pink insulation) or rock wool (ie: Roxul) or 8 inches of cellulose (ie: blown insulation), at the very least.  To help the insulation work properly, make sure it’s evenly distributed throughout your attic. It can cost as little as $800 to add DIY-batt insulation to a 500 square foot attic, says Pervan, but you can save as much as 15% off your heating bill.

(If you’re on board with all these fixes, but your attic is insulated with loose fill, you may need to call a professional to weatherize and seal the attic.)

Step 3: Detect drafts

Now that you’ve sealed up your attic, you’ll want to turn your attention to any drafts that may exist in your home. You can pay $100 or more for a blower test—a company comes in, creates a zero-pressure environment in your home, then turns on a big fan, and searches your home for leaks—or you can turn on all the exhaust fans in your home, light a candle, or incense stick or use a draft detector and follow the smoke.

As you walk around your house, watch the smoke. If is starts to drift sideways when held up to windows, doors and electrical outlets then you have a leak. You can easily plug leaks yourself using weather stripping, caulk and expandable foam and should cost the DIY-homeowner less than $40—but will save you as much as $350 in heating costs each year.

The third piece in this series on the Ultimate Heat Efficient Home will focus on technology and decorating options that will actually help increase your home’s heat and energy efficiency.

Want to read the first installment in the Ultimate Heat Efficient Home guide? Go here.

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