How do you attach a large amount of insulation to a concrete wall?
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| Posted in Green Building Techniques on
The house I am building in zone 5a will have concrete walls (2 story) for high thermal mass. I would like the walls insulated to R-30, but am concerned about how to attach so much insulation. Will 5 inches of polystyrene get me to a R-30 and how will it attach to the walls? Is there a better way to insulate concrete?
Deni
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Replies
Denise,
Hilti makes a good system for insulation up to 4 3/4 inches thick. It's called the Hilti IDP Insulation anchor.
The Hilti IDP system is the one recommended by energy expert Marc Rosenbaum.
I'd be interested to hear from GBA readers about fastening systems for insulation that is 5 inches thick or more.
Martin,
The IDP equivalent from SFS also works: http://www.sfsintecusa.com/products/architectural-fastening-systems/flat-roof-fastening-systems/
Attaching the insulation to the wall is the easy part. Hanging the facade is the next question.
The The Heco Therm screw is a quick way to hang both the insulation and facade batten onto a wood wall. See our draft video at: http://www.youtube.com/user/smallplanetworkshop/featured
Sadly for me it only works on wood.
Happily for me, I just found a really great system in Germany. It's an extremely low thermal conductivity facade support system that is intended to be used with exterior mineral wool wrap. The application ranges can fit thin layers to exceptionally thick: 14" if I remember correctly.
The system has a version for wood battens for wood siding, or extruded aluminum for commercial facades. All of the supports are stainless steel, triangulated, and will anchor to wood or masonary.
I think this would not work well for EPS, but would work well for mineral wool, which I think is probably a better exterior wrap insulation in the long run.
See the attached lit and my picture of their display.
A question on the Hilti anchors (I'm planning to anchoring something like 3 inches of polyiso into concrete block). Can you use them to also anchor the strapping/furring for a rainscreen gap? Basically I'm thinking that you drill through the wood (3/4 inch), the 3" foam and into the concrete, then bang 'em in. That might mean using slightly longer anchors in those spots.
I suppose the real answer is in figuring out the loads of the rain screen assembly, spread over the furring and allocated to each anchor in the furring.
German system looks very German :)
James,
I think the most common method of installing furring strips on concrete walls is with Tapcon screws. Tapcon screws are available up to 6 inches long:
http://www.concretescrews.com/tapcon-prices/blue-standard-tapcon.aspx