Build with Mark - Install Insulation Correctly.

Ask Mark a Question Are You Building a Home, Adding On, Repairing or Renovating? Click the ask Mark a question link above and submit your question. It'll be featured here on the site in the subject category.

	© Mark Saville 2006	Install Insulation Correctly.
			Fiberglass insulation works to keep your heat in your house in the winter and keep the heat out of your house in the summer. It does this by creating a dead air space in your wall or ceiling cavity that is resistant to air travel. In the winter when all the windows and doors are closed and depending on whether your house has a positive or negative pressure, there can be a lot of air movement from the inside to the outside taking your precious heat with it.
	For this reason insulation must be installed tightly and correctly. There should be no voids in between the insulation and the outside wall that will cause a convection current and a great place for mold causing moisture to build up and all joints between the insulation itself need to be tight with no visible space at all. If your insulation is installed correctly you should see no black lines between the insulation itself or the insulation and framing members. If you see a black line then it's not tight enough. The photo to the left shows insulation installed incorrectly. Notice the poly pan behind the electrical box which is a must when installing your electrical boxes and vapor/air barrier. This will help to keep the cold air out. Remember, your insulation keeps heat in and the air barrier keeps drafts and cold air out.

To install insulation correctly there should be no visible spaces between the insulation and itself or framing members. In cold climates you can actually see frost form on the inside of the vapor/air barrier when the warm air comes in contact with the cold air from the outside as a result of insulation not fitting tightly. The dew point (a temperature where water vapor becomes visible) is created on the interior side of the poly.

The right way to install insulation.

Another point to make about installing insulation correctly is in the winter months in colder climates, fiberglass insulation should not be left uncovered if there is heat in the building. Frost will form on the inside of the wall sheathing causing mold to grow once the vapor/air barrier and wall finish is installed. Cover the insulation as soon as possible with the poly barrier and if you install the vapor/air barrier and drywall on the ceiling so you can blow in insulation later make sure you get the fiberglass blown in as soon as possible or moisture will form on the cold side of the barrier.