Prevent heat loss with exterior insulation

By Cold Climate Housing Research Center Staff

The “Ask a Builder” series is dedicated to answering some of the many questions Fairbanks residents have about building, energy and the many other parts of home life.

These days, it is popular to put foam insulation on the outside of buildings.  How did all this come about? 

      A building loses heat through its framing, which is called “thermal bridging.”  Wood has less insulative value than any kind of insulation.  For instance, a wood stud has an R-value of 1.25 per inch.  If a building has a standard framed wall, whether it is 2×4 construction, or 2×6 construction, the studs span from the interior of the wall to the exterior of the wall. For a 2×6 wall, that would give you an R-value of about R-7 where the stud is located.  If you were to take all the studs in a wall and stack them side by side, you would have a wall that is 11-25% wood depending on how it is built.  Even if a wall is full of R-21 fiberglass insulation, the insulative value of the wall is dramatically worse when you average in the less insulative value in the wood.

      At least 20 years ago builders began experimenting with putting insulation on the outside of homes as a way to stop heat loss created by thermal bridging. Adding foam to the outside of a wall “wraps” your home in a continuous layer of insulation, thus preventing other building materials from conducting heat to the outside and cutting down on the air leaking out of your house.  This technique has been used in many cold climate regions.  The PERSIST (Pressure Equalized Rain Screen Insulated Structure Technique) is an exterior insulation technique that has been used in Canada for many years, while the REMOTE (Residential Exterior Membrane Outside Insulation Technique) Wall System is popular here in the Interior. 

Where can I recycle glass in the interior? 

      Recycling glass is a challenge because the material is heavy and difficult to ship out of Fairbanks and then out of Alaska.  Also, Anchorage recently ended their glass recycling program, in part because the market for glass is currently not very good. 

      Here in Fairbanks, there are a few small artisan-type businesses that are reusing glass, but they cannot handle large volumes and typically have more than they need already.  However, the Borough Recycling Commission is looking at ways to use glass here locally potentially as road fill and construction fill.  These plans will take time to develop, so if you have any input, contact the Recycling Commission through the Fairbanks North Star Borough at 459-1000. 

Alaska HomeWise articles promote home awareness for the Cold Climate Housing Research Center (CCHRC).   If you have a question, e-mail us at  You can also call the CCHRC at (907) 457-3454.