Insulating the Shell - Attic, Wall, Basement


Insulating the Shell and Sealing Leaks

There are several steps you can take to improve your comfort, reduce your heating and cooling bills and reduce your footprint on planet earth. While some are best done during the construction of the home, such as increasing the insulation value of your walls and improving the "air seal" of the complete house, there are still a selection of items you can do today.

Insulating Your Home

Tools - you'll need

  • a straight edge - as a guide for cutting the insulationinstallation tools
  • utility knife
  • portable work light
  • pole or rake - to help move the insulation into place
  • work gloves
  • loose-fitting, long-sleeved shirt
  • safety glasses
  • dust respirator mask
  • staple gun for insulating walls


For northern climates, the attic should have an R value of 49, less for southern climates, but still at least R25. That's 12 to 24 inches of insulation, depending on what you use. Use boards or plywood on top of attic insulationceiling joist as a work platform. Move boards as necessary to complete a section at a time. Start at the outer edges and work toward the center. If spaces between the joists are already filled with insulation, lay the new insulation perpendicular (crosswise) to the joists. If the joist cavities aren't completely filled, fill them first, then run a layer over the top, crosswise. Be careful to leave at least three inches between the insulation and heat producing devices such as recessed lighting, metal chimneys, gas water heater flues, etc. And don't forget to cover the "cover" or door that you used to get up into the attic. Also, don't block the air vents at the outer edges. You need to keep a proper flow of air for ventilation.


If the walls are covered, I'd leave this to the professionals. There is a good selection of products that can be sprayed into these empty cavities to increase their R value and reduce drafts. If the walls are "open" you have a couple of options. Fill the space, based on the thickness of the joist or add to the joist to increase the overall insulation that can be added. Adding onto the existing joists will allow you to install a vapor barrier in the correct place and will increase the total R value of the walls, there by reducing you heating and cooling bills by more. However, most people will opt to fill the existing open space with insulation and call the job done. Measure the width between the studs and the total depth of the wall. Fibreglass insulation comes in a variety of widths and thickness. Make sure you purchase the size that fits your stud spacing. You can also purchase fibreglass bats that come with a paper backing. Bats with a paper backing are best for walls as you can staple the bats into place so they don't sag and leave a gap at the top of the wall.


Walls in the basement are treated the same as other walls. Make sure the insulation goes all the way to the floor and not just at the top of the wall. Some contractors in the past, would only insulate the porting of a basement wall that was exposed to the outside air. The stopped insulating the wall where it came in contact with the earth (cement wall). Basement ceilings can be insulated if you keep the basement cooler (unfinished) or to reduce the transfer of noise between floors. Basement Floors - before you insulate the floor, you need to consider water damage. Have you ever experienced water in the basement? Are there any signs of past flooding? Are you planning to use the basement for a living area? If you are confident that there will never be any flooding in the basement, you can go ahead and add a sub floor with insulation. A foam insulation will likely work best for this area, given the reduced thickness available. If you think there could be a possibility of water in the basement at some time, I'd see a flooring specialist. There are new products (mats, webbing) specially designed for damp basements.


Sealing Air Leaks

House air leakage

Many air leaks and drafts are easy to find because they are easy to feel, like those around windows and doors. Holes hidden in attics, basements, and crawlspaces are usually bigger problems. It's fairly easy to perform your own Home Air Pressure Test to find air leaks. Follow this link to see how: Home Air Pressure Test

Seal these leaks with caulk, spray foam, or weather stripping for a big impact on improving your comfort and reducing utility bills. Click on the picture to see common air leak locations that you should seal.


Applying foam weather stripping around doors is easy. The foam strips come with self-stick tape on the back. Pick the size you want, then peel and stick. Check the bottom of your doors for leaks as well. Sealing the threshold takes a bit more work. Measure the size of your opening, then visit your local hardware store. They should have a good selection of threshold strips that simply screw into the floor.


Stationary windows should be well caulked. Buy the expensive caulking as it will do a better job, last much longer and pay for itself in energy savings. It's also easier to work with. You should caulk both inside and outside of all windows. Caulking is available in various colors as well as "clear". I found a brown caulking that closely matched the exterior paint color and used clear caulking around the inside of the windows.


Check the outside of your home for possible air leaks. Pay attention to pipes, electrical outlets and conduit. Also pay attention to joins of different materials, such as the joint when bricks meet siding. Look for cracks in mortar, foundations and siding materials. When in doubt, add caulking.


People are sometimes concerned about sealing their house too tightly. This is very unlikely in most older homes. A certain amount of fresh air is needed for good indoor air quality. There are specifications that set the minimum amount of fresh air needed for a house. If you are concerned about how tight your home is, hire a contractor, who can use diagnostic tools to measure your home's actual leakage. If your home is too tight an air-to-air heat exchanger will be recommended.

After any home sealing project, have a heating and cooling technician check to make sure that your combustion appliances (gas- or oil-fired furnace, water heater, and dryer) are venting properly.


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