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Ask the Experts!

15 October 2008

Natural gas prices are predicted to rise 30-50% this heating season – so no wonder we’re getting questions about insulation!

“What’s your opinion of a combination of soybased foam and blown-in cellulose to insulate a century-old attic with some fiberglass batts already in place? It was suggested by our energy auditor but I”m having trouble getting contractors to come on board.”

I like the idea of using at least 2″ of a closed cell foam after removing all existing insulation to get a great air barrier before adding a less expensive cellulose insulation.  Two inches of closed cell foam will also provide a vapor retarder.  I am not familiar enough with soy based closed cell foams to recommend them.  I would want to know how long they have been on the market and what their track record is.  You can expect to pay approximately the following:

$3 to $4 per square foot for removing existing insulation, adding 2″ of closed cell foam, adding cellulose to R50 total
$1 to $2 per square foot for removing the existing insulation, sealing the large bypasses using different strategies and blowing 14″ of cellulose alone
$0.5 per square foot to perform the measure listed above by doing it yourself

If you have trouble finding insulation contractors to do the work, try insulation contractors listed on the mbpa.us website.

Answer provided by Paul Morin, Senior Building Analyst at the Center for Energy and Environment.

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