foam insulation in an old house (1810)


Old 01-21-02, 11:11 AM
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foam insulation in an old house (1810)

I'm buying an old house (1810) in NH and it has no insulation in the walls. I'm leaning towards blowing in foam insulation.

I'm assuming that the plaster walls behind the wallpaper are in good shape and would like to keep them if at all possible.

My concern with using foam insulation is that I'm worried that the plaster on the unfinished side (the inside of the wall) will prevent the foam from reaching all the nooks and crannies.

Insulators I've spoken to only spray insulation in open cavities for just this reason.

Does anybody have any experience with blowing in foam insulation into old houses? (post and beam with plaster walls)

Are my worries unfounded?

thx, glm
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Old 01-25-02, 02:21 PM
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The foam they spray into walls today is much different than the foam they used in 50's and 60's. Many of the concerns we hear today about foam insulation stem from that era.

With open wall cavities they mix the foam so that it expands and fills the cavities within a few seconds. Within a few minutes, the foam is hard enough to scrape off the excess. If you ever seen the equipment used for this, it looks like two hoses that is attached to a nozzle that mixes the two chemicals, just before it's applied.

With closed wall cavities, they mix the chemicals so the foam expands slowly and fills the cavity. The real problem with doing this is finding an experienced contractor that knows how to mix the chemicals properly. If not done properly, you get voids or gaps in the insulation and might even crack your plaster.

You should ask the contractor how long they have been in business and how many jobs they have done. References is a must and you should check with the Better Business Bureau.

A more common product used for walls is cellulose and they use a technique known as dense packing to accomplish the filling in nooks and crannies. You'll find more contractors that are more experienced and familar with cellulose than foam insulation.
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