Is there any point in insulating the outside of a poured foundation with
styrofoam? The house has a walk-out basement with in floor heating and will
be finished in the future. I was planning on insulating the inside with
styrofoam but before we backfill should I insulate the outside? This is in
eastern Canada. Thanks
The more insulation the better. It is good to have some on the outside. For
some good information on insulation, take a look at the system of insulating
concrete forms. Even if you don't use ICFs, the same info applies for
insulating avlues. www.integraspec.com or www.polysteel.com or
About 20 years ago I had a house built. I asked them if it was OK if I
insulated the outside before they backfilled. They OK'ed it and I did.
About 10 years ago I had another house built by the same builder; this time
they they were insulating all their new homes using the same materials and
methods I used. It was then a feature.
It will not change the world, but it should reduce utility bills a
little and may help protect the waterproofing on the foundation wall.
It if frequently done in high end houses. However, make sure that the
contractor is not going to use a "stone slinger" to cover the drainage pipes
around the foundation. These trucks fire the gravel at high speed and can
reach considerable distances (which is why many contractors like to use them
to reduce manual labour in hard to reach areas). The downside is they will
destroy any foam that you put on the outside as fast as a sandblaster can
Also consider laying foam insulation horizontal - from the foundation out 4
feet and about 1' down from the finished grade level. This slows down /
blocks frost from going down the side of the foundation. No frost = no
There are some web sites that talk of the use of foam on the exterior of
Just as I said. I approached the builder as the foundation was being
built and asked if I could add the insulation, (I used an foam insulation
available in large panels that was identified for under ground use). The
builder agreed as long as I finished by the Monday when they were scheduled
to backfill. I used some of the same mastic they had used for waterproofing
to hold it up until the backfill was done.
My next home about ten years later was by the same builder (not great
homes, but good value) and the same kind of insulation was listed on their
standard feature list.
Here's a good article on the dos and don'ts of insulating foundation walls.
Fairly interesting if you think how most contractors insulate your basement.
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