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Can continuous insulation be installed to the inside in a cold climate?

DCBL Steve | Posted in Green Building Techniques on

I am working with some builders trying to achieve ENERGY STAR v3 on existing homes. These are structural brick homes (12″). The exterior walls were all framed out with 2×4. The builder wants to put r5 continuous to the inside and then dense pack or wet apply cellulose in the cavity with the cellulose being I contact with the structural brick. I don’t like this approach and recommended that they either take down the framing and insulate the structural masonry wall to the IECC minimum for mass walls of R17 directly adjacent to the brick (rigid foam board with seams taped in order to not violate historical preservation) or insulate to r5 cont. against the brick and frame out the wall to the inside of the foam board and then insulate to at minimum to r13 with whatever you want as long as it meets RESNET GII.the only other scenario I would even consider, and that was on the condition that I can get it on some valid authority, would be to somehow install some air barrier material to the backside of the framing adjacent to the brick (15# builder paper, tyvek, the builder suggested 1/4 inch foam) then insulate to r13 with r5 cont. to the inside adjacent to the conditioned space. It would be an air tight assembly so the cellulose or any fibrous insulation would have a better chance of performing, but I don’t know if it would work in Climate zone 5. Is this a decent strategy?

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  1. GBA Editor
    Martin Holladay | | #1

    Insulating older brick buildings is tricky. I recommend that you read the following article, which should answer many of your questions:
    Insulating Old Brick Buildings.

  2. DCBL Steve | | #2

    Thanks for your response. The article was very helpful. The article promotes spray foam to the interior of the brick wall. The homes in question are in a Historical District in CZ5 so spray foam is not an option. I have done some research and am confident that insulating structural brick to the interior can be done effectively with rigid foam board attached directly to the structural brick.

    My main concern would be a situation where a builder has framed out against the brick without installing some sort of air impermeable insulation against the brick. This approach seems unconventional and not best practice so I am reaching out for confirmation that this approach would perform in CZ5.

    I did get a confirmation outside this forum that folks have put the continuous rigid insulation to the interior in CZ5. I would add the inclusion of some sort of air impermeable product to be installed to the backside of the framing that will be adjacent to the structural brick (a Class II or III vapor retarder that is durable and can be an effective drainage plane, #15 felt, Reflectix, NO POLY! ). Then air seal the air barrier at the framing so the fibrous insulation will be installed in an air tight assembly. A visual inspection of the existing structure with recommendations for proper gutters, downspouts, grading, and flashing around doors and windows and I think this approach could work.

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