Basement Insulation
BASEMENT INSULATION

Foundation/ Band Sill Insulation

Foundation Insulation is often overlooked. Many people have the misperception that the foundation wall has a good R-Value, due to its thickness. The truth is, the concrete or block walls have very little R-Value. Typically a 10” thick foundation wall only has an R-Value of between 1 and 2. This results in poor insulating performance and explains why the basement is so cold in the winter.

To address this issue you need to insulate it properly. Common questions include: Where to insulate and to what R-Value and what materials are right for the job. Lets start with where:

Foundations that are a part of the Thermal Boundary should be insulated from the sill plate to 4' below grade.

The type of material that is right for the job will vary depending on how the wall is to be finished as well as the budget for the project. If the basement wall is to be left unfinished it should be insulated with foil faced fiberglass board insulation. The foil provides the ignition barrier and has the appropriate R-Value.

If the wall is to be finished you can use Fiberglass Batt Insulation, foil faced fiberglass insulation board or open cell spray foam. Good, better and best, respectively.
Band Sill
Band Sill, which is also known as Sill box, Rim Joist or Band Joist among other things, is the area at the top of the foundation wall where the floor joist meet the rim joist. This is another area often overlooked when it comes to Insulation. Again the question is: what are the correct products to use to properly insulate this area?.

Technology has had a great impact on Insulation with the development and advances in Spray Foam. The Band Sill is the one place in most homes where Spray Foam can be utilized. (With the exception of new construction.) Again, a great Thermal Boundary consists of an air tight seal and plenty of Insulation. Spray Foam accomplishes both.

Most homes were built using only Fiberglass Batt to insulate the sill box. This is the wrong approach because it does nothing to cause an airtight seal so the Fiberglass just acts as an air filter. Take a look at your home’s band sill area and see if the fiberglass is dirty or discolored. This is an indication of air flow and tells you that the sill box needs addressing.
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Band Sill Insulation
Band Sill Insulation
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Air Sealing Sub Floor Penetrations
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Blown In Cellulose
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Finished Cellulose Insulation
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Attic Hatch Blocking