Sunday, July 22, 2012

Finishing the wall insulation

The insulators were back last week putting in the final layer of dense pack cellulose between the studs of the inner stud wall.  This completes the EPS/Polyioso sandwich with dense pack cellulose bread.

The video below shows the cellulose being blown between the studs and the cloth batting.  Behind the studs, you can see the aluminum foil cover on the sheets of Polyiso from the middle layer of insulation.

This brings the total wall insulation of our 1' thick double stud walls to R 48.  Is this a lot of insulation?  The framer has commented that we could have insulated standard 4 houses with the amount of insulation in our Passive House and that was before this last layer of dense pack went in.  The CT Energy Efficiency Fund gives rebates for "High Performance Insulation".  Their minimum requirement is R 21.  We have more than double the insulation of what is considered a very well insulated home.  One of the fundamental principles of Passive House is super insulation.  We're definitely meeting that requirement.

The basement walls (where we'll lose less heat) are insulated with 2 inches of Polyiso up against the foundation walls and dense pack cellulose in between 2x6 studs.  These walls have a combined R-value of R 32.  Underneath the basement slab is 5 inches of EPS at R 28.  The slab doesn't meet the foundation walls creating a thermal break that prevents heat from being conducted from the slab to the foundation.

The attic is going to be insulated with loose pack cellulose to R 83.  This should do wonders for keeping the heat from escaping to the roof during the cold months and infiltrating from the roof during hot months.  Again, the CT Energy Efficiency Fund requirement for ceilings is R 40, so again, we have more than twice this amount of insulation.

According to our builder all this extra insulation costs about $10K more than insulation would on a standard house.  We think that the upfront cost will more than pay for itself over the house's life.  In addition the extra insulation will provide a more comfortable place to live.

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