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Are Insulated Concrete Forms and Gigacrete panels good?
Dallin Sumpter
Feb. 21, 2019Updated: Aug. 3, 2020
I want to build a house to passive house standards and keep it to a relatively small budget by potentially doing some of the build myself. I stumbled upon the history of ICFs and Gigacrete while researching building materials, but haven't seen a lot of passive houses built with these type of insulating materials. Is there a reason why? Insulating concrete forms would seem to be a pretty efficient method of building houses, and can be air tight without a lot of additional work, dont have thermal bridges, and they tend to have a hard time catching fire (important where I live). I'm looking for an educated opinion because I am such a construction rookie - but ICF as a construction system has got me interested.
Typical ICF blocks don’t offer nearly enough thermal protection to meet Passive House performance requirements, that's likely contributing factor as to why you don't see as many. What manufacturers usually offer is about R22, and getting a home Passive House certified would generally need about double that. It is also not the most affordable construction method, so given the higher costs of shooting for PH levels, builders often look for a higher R value per dollar wall assembly.
If you are planning ICF and Passive house, I would suggest having a look at ThermalWall, a rigid insulation panel designed to attach to ICF blocks (above or below grade) that can help you meet performance targets. I'm not sure if it has achieved PH certification yet as a product, but it was conceived specifically to make ICF a viable option for Passive House.
I'm also planning to build a house, not necessarily up to passive house standards, but as green as economically possible. For the exterior wall I'm giving strong consideration to using Nexcem ICF wall forms. You may find technical details online about this pioneer of ICF blocks and ICF construction and videos of a builder describing how he used Nexcem ICF wall forms in construction. Note, Nexcem was recently known as Durisol, so you may find additional information online under that brand - or if you're interested in the definitive history of ICFs blocks & ICF Construction including Durisol, that's here..
I looked at Nexcem too but I found lots of comments in forums about the blocks when they were Durisol - apparently they can shatter easily unless they are handled very carefully and building with them looks like hard work! see http://www.theenclosure.ca/relief-2/ Also, they wont get you above R22, which isn't helpful if you want a well insulated envelope...
A few years ago I built a very large home using Durisol. We had more than 12,000 SF of Durisol walls and experienced none of the shattering problems you cite. A crew of five experienced masonry workers put up the walls in about 6 weeks. We lived in the home for eleven years and it was a fantastically energy efficient home - but then that is in comparison to a standard stick built home with 4 inch insulation and which leaked air like a sieve which is all we had before. I hadn't realized before reading the article mentioned above that Durisol ICF had such a long history !
Thank you!