When first searching on the internet for green building processes and products, insulated concrete forms (ICFs) came up again and again, especially on the green building forum. I suspect that the forum was begun by an ICF manufacturer. Basically, they are two walls of Styrofoam tied together by plastic grids. They go together like Lego, even having the peg shapes and depressions. Steel rebar is tied in between the Styrofoam. Doors and windows are blocked out. Once braced from both sides, concrete is poured into the forms, which stay on the exterior and interior surfaces after the concrete cures. A waterproof membrane is applied to the exterior, and a second dimple board waterproofing is added where the soil will touch the wall. It can be backfilled shortly after pouring. The roof is built onto the top of these walls in a normal manner. The insulation/vapour barrier is built in, and wall finishes are applied directly to the Styrofoam.
Two years ago, when I first started talking to building contractors, I asked their opinions about ICFs. I heard responses that discouraged me from having our house built this way. The main reason was that any alterations down the road would be extremely difficult, cutting through concrete. I also heard that the Styrofoam on the outside provides a very cozy home for all kinds of insects and critters, an assertion that the salespeople refute.
However, I was still intrigued, and have decided to have my 20’x20’ studio built in this way. It will be roofed by our kitchen garden, accessible by a walkway from the main level sundeck.
Our next door neighbour built his foundation this way, and it looks so easy, especially after viewing the instructional video.
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