Technical Papers

Attic Insulation in Cape Cod Granby, CT

Monday, October 24th, 2016 by Brendan Fogarty

This homeowner contacted us to help him make his home more comfortable and energy efficient year round.  Our Building Science Expert did a comprehensive evaluation of his home to determine why his rooms on the second floor were very uncomfortable and inconsistent with rooms on the first floor.

Generally, Cape Cod construction homes are the most inefficient homes due to the amount of unconditioned spaces on the second floor.  Unconditioned spaces are considered outside spaces as they are not heated or cooled.  

During the evaluation, the Building Science Expert noticed the knee walls or crawl spaces adjacent to the bedrooms and bathrooms on the second floor were insulated with a minimum amount of fiberglass insulation.  Wind Washing was evident on this inferior insulation.  Wind Washing is evidence of airflow through the stack effect.  Dirt was noticed around all the edges of the fiberglass insulation which was acting as a filter, not a convective insulation.

We installed our Super Kneewall with SilverGlo to the knee walls and crawl spaces.  A kneewall is the triangular space under the sloped roof and behind the wall of the room.  Our SilverGlo is expanded polystyrene foam insulation with graphite infused in the foam.  This increases the R-value as compared to regular EPS foam.  

The attic triangle in a Cape Cod construction is a very tight space. In order for us to effectively treat this space, we dense packed with TruSoft Cellulose insulation from the ridge of the roof.  Dense packing is used when air sealing for convection loss is not possible.  We remove the ridge cap and access the attic and the slope of the attic from the roof line on the exterior of the home.  We blow insulation into the attic framing cavities fully packing the voids.  Using this treatment allows for hysteresis.  Hysteresis is vapor escaping through the top of the house for ventilation.

Additionally, in the basement of this home, the significant amount of humidity entering the house through the rim joist was causing mold spores to grow by raising the relative humidity above 70%.  Because the concrete foundation is a porous material, temperature differences between the top of the foundation and the bottom of the foundation causes condensation in the summer.  

By air sealing the entire rim joist with our closed cell spray foam, we stopped the humid air from entering the home in the summer and the cold dry air from entering the home in the winter.  This will keep the basement more comfortable and effectively more energy efficient.

This homeowner was able to notice a significant difference in the comfort of his home immediately.  He will realize lower heating and cooling costs and his home will be more energy efficient.


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Fogarty's Home Services
800 Prospect Hill Rd
Ste E
Windsor, CT 06095

Fogarty's Home Services
258 Old Lyman Rd Suite B
South Hadley, MA 01075
Northern CT, Berkshire County and Greater Springfield MA