Benefits of Building with ICFs
Builder Josh Salinger explains how and why he's creating the foundation for this new energy-efficient home out of insulated concrete forms.
Josh Salinger, owner of Birdsmouth Design-Build, is on-site in Portland, Ore., to discuss the benefits of using insulated concrete forms (ICFs) to build a foundation for a small, energy-efficient building. ICFs are modular concrete forms that permanently remain in place to provide insulation for the structure they enclose. The ICFs are used instead of traditional forms for pouring a concrete wall. Each ICF block consists of a pair of expanded polystyrene (EPS) rigid-insulation slabs separated by plastic struts to create a void for pouring the concrete.
This project is on an net-zero-energy accessory dwelling unit (ADU), which will be a secondary housing structure built on the back of this single-family residential lot. ADUs are often rented out and used as supplemental income. Other times, they’re used for expanding families. In this case, the ADU will be be a home for grandparents who want to live closer to their children and their newborn grandchild.
Check back soon to see more videos by Josh about the construction of this home.
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Josh never once warns viewers that ICFs are not suitable for all climates. He fails to explain that with half of the insulation on the exterior of that heavy concrete wall, the homeowner is partly heating that concrete.
In a cold climate, that is a lot of energy that goes into heating that heavy mass every time the home is "re-heated".--on returning from work or in a vacation home that is only used on weekends.
If one uses ICFs in a cold climate, the inside face of the wall should be insulated to the appropriate standard, regardless of the insulation on the exterior.
Interesting. I participated in a presentation at an ACI conference several years ago with a couple of building scientists and the question came up of where the insulation is best located for foundations. The result - for all climates - was it just didn't matter much. Insulation on the outside and concrete on the inside vs. insulation on the inside and concrete on the outside vs. ICFs with concrete in the center vs. insulation in the center with concrete on both the inside and outside.
Have you seen a study of the energy performance of ICFs in different climates and what would be a better system for each climate zone (foam location / concrete location)?
Mike, excellent, very credible reference and reminder that insulation location on a foundation is irrelevant!
Thanks, Mike. I am a bit stumped as to which climate zones ICF's wouldn't work for. Maybe it is the requirement for a higher R-value in the colder climates? This could be mitigated with a thicker ICF. It is true that 60% of the thermal losses of a slab occur at the slab edges and it really doesn't matter if the insulation is on the inside, middle or exterior of the stem wall. So long as the interior conditions are thermally separated from the exterior environment the goal has been met.
On this particular project we are using a floating plywood slab in lieu of concrete which would further break any losses at this condition.
Suburbanguy, if you have some information on this I would be curious to see it.
Thanks!