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Interior insulation with old solid brick walls

LauraZone5 | Posted in Energy Efficiency and Durability on

Thought this could be a lively discussion.

I recently ran across an item touting a way to insulate solid brick walls on the interior using a drainage mat on the interior, with spray foam and studs inboard of that, and drilling drainage holes thru the brick to the exterior. (See attachment.) As an architect practicing in climate zone 5 (NYS), I found it intriguing, yet I’m skeptical of its practicality and cost. We happen to have a ton of old brick warehouses, factories, etc. which are suddenly in demand for conversions to loft apartments, so getting this detail right is important. Currently we spec 1″ rigid XPS attached directly to the inside of brick wall, then 2×4 studs with kraft-faced batt, then GWB as air barrier. This satisfies the Energy Code and our clients’ budgets, but it probably doesn’t let the brick breathe well on the interior side.

How would you compare the two methods?

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Replies

  1. Expert Member
    Dana Dorsett | | #1

    The amount that the brick needs to "breathe" toward the interior varies with how much direct wetting it gets, and how cold the climate is. Freeze/thaw spalling is a much bigger issue in climate zone 6 & 7 than it is in climate zone 5.

    But it doesn't hurt or cost a whole lot to install 1/4" or 1/2" of rainscreen mesh between the XPS and the brick in your standard stackup. It also doesn't hurt to use 1.5" EPS instead of 1" XPS, reducing the environmental impact by a large margin, with a more stable R-value over decades.

  2. GBA Editor
    Martin Holladay | | #2

    Laura,
    These issues have been extensively covered at GBA. Have you seen these two articles?

    Insulating Old Brick Buildings

    Nuggets From the 2015 Westford Symposium

    The relevant section in the second article ("Nuggets From the 2015 Westford Symposium") begins about halfway through the article, in the section under the head that reads, "Insulating old buildings with structural brick walls." That section of the article describes the work of Toronto researcher Kim D. Pressnail. Pressnail gatherered data on the insulation approach you describe.

    For the time being, as researchers continue to research this approach, I would call Pressnail's approach experimental. Use it at your own risk. In the meantime, conventional advice can be found in the first of the two articles I linked to.

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