I am volunteering with Habitat for Humanity. The house’s will have insulated concrete forms in the basement only. I am wondering if the benefit of using this system is greater than using standard concrete forms that have 2″ foam panels on the outside? Opinions ?
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Replies
Insulated concrete forms
It depends where the home is being constructed. They are best In a very temperate climate like the northern west coast where it doesn't get below freezing.--(I don't live there, mindyou.) However, if they're used where the weather gets cold, they have a big drawback which is never discussed. That drawback is that half of the insulation is on the outside of a very massive wall. Whenever the homeowner leaves the home and turns down the thermostat, those massive walls gradually give up their heat and the house takes quite a while to cool down. (Now granted those walls aren't at room temperature, because there is some insulation on the inside basement walls, but they are still warmer than if ALL the insulation was on the inside of the wall.) When the homeowner returns and turns the thermostat up, it takes a loooonnnggg time to heat those walls again. Furthermore, why does anyone want to spend money heating those massive walls in the first place. It is usually best to heat the minimum mass possible.
There is nothing wrong with using the insulated forms, but be advised that those basement walls should be insulated on the INSIDE as though there was no insulation on the outside of the walls.
The main advantage to ICFs is that they can be set up with a minimal crew -- often just 1-2 people working DIY. They also have less "thermal bridging" than solid block, but the difference isn't terribly significant.
DIY with ICFs can be problematic. They need plenty of bracing. If not done well you can end up with some pretty awful foundation walls.
If DOW gives away ridgid foam sheets for habitat houses I can't imagine why ICF's would be bought and paid for instead of free foam! Personally I'd go back to the building committee and get everyone on the same page. ICF's won't give you anything that an inexperienced crew will want to deal with.