Thoughts on Insulation

“Insulation: Thermal Performance is Just the Beginning” [


Vol. 14, No. 1] was another very informative article. Some specific comments:

1) Regarding polysio insulation, if the conductivity of the hydrocarbon blowing agent is indeed lower than HCFC-141b, then the insulation performance should be better, not worse.

2) I’m less convinced than you that using used newsprint as insulation is downcycling. In a way, permanent building insulation is a higher use for wood fiber than a daily newspaper!

3) I make my choice of insulation material based on a number of factors, many of which you touched upon in your article. In any type of construction, the ability to ensure that the building will get a continuous, robust, effective air barrier is a major input to my choice. In wood-frame housing, I use a lot of cellulose, which I think is the best environmental choice, and very effective. I use it when I know the builder and the cellulose subcontractor. In wood-frame applications where I think it’s unlikely there will be good attention to air-barrier details, I choose low-density spray polyurethane foam (SPF), like Icynene or Demilec. I’ve been asking for exterior application of high-density SPF in cavity-wall buildings, and layered, rigid polyiso boardstock in roofs and over steel framing, so that I have the best likelihood of getting an airtight building.

Marc Rosenbaum, P.E.


Meriden, New HampshireEditors’ reply:

Marc wins last month’s “catch the error” award. The conductivity of the hydrocarbon blowing agent is higher—not lower—than that of HCFC-141b. We have made the correction in our online BuildingGreen Suite.

Published March 1, 2005

(2005, March 1). Thoughts on Insulation. Retrieved from https://www.buildinggreen.com/op-ed/thoughts-insulation

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March 18, 2005 - 8:02 am

having used low-density foam (Icynene) in the renovation of a building framed with 2x4 walls, I was shocked by the quantity of waste that had to be shaved off. as far as I know, this waste was neither recyclable nor re-usable. i used high-density foam (Polarfoam) in the next project, even though it was a new house with 2x6 walls, and found it far more satisfactory from that point of view, as well as being significantly higher in R-value, and a more effective vapour barrier, to boot. Disadvantages are the (even) higher cost and offgassing from the blowing agent.
Incidentally, building inspectors here are requiring a vapour retardant paint with high-density SPF, principally because of the discontinuity of the vapour barrier where the foam doesn't cover the edges of the studs.