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Video: Installing Rigid Foam Under Footings

Posted on Oct 25 2011 by Skylar Swinford

This construction site video of the Karuna House in Yamhill County, Oregon, demonstrates installation of a geofoam foundation that will superinsulate the bottom of the building envelopeExterior components of a house that provide protection from colder (and warmer) outdoor temperatures and precipitation; includes the house foundation, framed exterior walls, roof or ceiling, and insulation, and air sealing materials. and help the project achieve Passive HouseA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates. and Minergie-P-ECO certifications.

Lead Carpenter Scott Gunter narrates the process of:

  • screeding out gravel,
  • back dragging with rake as needed,
  • compacting gravel,
  • marking outside foundation wall line on foam,
  • setting and aligning geofoam, and
  • drilling and pinning geofoam into place.

The Karuna House is designed by Holst Architecture and built by Hammer & Hand.

For more information on this topic, see Foam Under Footings.

Installing rigid foam under a footing in Yamhill County, Oregon

Karuna Passive House - geofoam foundation installation with Hammer & Hand's Scott Gunter from HammerAndHand on Vimeo.

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Oct 30, 2011 1:48 AM ET

What psi foam is used? It
by John Klingel

What psi foam is used? It would be nice to see how they build the footer forms, etc, as well.

Oct 30, 2011 11:11 PM ET

Foam PSI
by Skylar Swinford


Thank you for checking out the video. Under the footings we are using 2.40-2.50 lb/ft3 EPS39 (Geofoam title) or Type XIV (EPS title). Under the slab we are utilizing 1.35 -1.50 lb/ft3 EPS22 or Type II.

More info can be found on the project website:

Hopefully by next week we will have a video of the next steps in the process. Our intent is to document the project each step of the way.

Nov 2, 2011 9:16 PM ET

by Tom Gocze

Is my concern of ants, termites or critters living in this amount of insulation founded?
We have done foam panel foundations, but wrapped the foam in 65mil EPDM. I was still a littler nervous about something getting in.

I wonder if building an uninsulated foundation system is more prudent and then superinsulating inside the basement or on top of a slab and decking over that. I don't know but wonder if it makes sense.

Jan 1, 2012 6:20 AM ET

Edited Jan 1, 2012 6:20 AM ET.

Two Big Reasons for "Outsulation"
by Kevin Dickson, MSME


Insulating the outside provides at least two hidden cost savings, in addition to adding beneficial thermal mass:

1. The concrete can be stained and polished for a durable, almost free floor surface.
2. Insulating the outside and applying Frost-Protected-Shallow-Foundation principles, the thickened edge slab can be only 16" deep throughout the US.

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