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Insulating a crawlspace with brick foundation walls

Chris Harrison | Posted in Energy Efficiency and Durability on

I have read a lot on this web site about the proper way to insulate a crawlspace; most of the responses seem clear for houses with cold climates or hot climates, but what about mixed climates (such as Virginia). We are very humid in the summer and cold/ freezing in the winter.
I have a 1900’s bungalow in Virginia (zone 4A) with a crawlspace that varies from 12-inches to 36-inches in height. The house is balloon framed with a foundation of brick priers and infill walls. The exterior walls are stucco on wood siding; the brick is also covered with the stucco on the exterior. Based on some preliminary investigation the foundation goes down about 2-feet into the ground. There is no signs of heaving or cracked bricks walls. The mortar has a heavy lime content.
I need to insulation the crawlspace, but as best I can tell, I have two options. One – insulate the floor joist with 9-inch batt (floor joist are true 2 x 10) or Two – insulate the foundation wall with 2-inch rigid insulation and cover the bricks. With either option, I plan on installing a 6-mil poly on the ground, and turning it up the walls and piers.
If I cover the bricks, I might be trapping water in the bricks and making it harder to access them in the future (mortar repair etc…)
Not sure what the best option is for a mixed climate with a brick foundation.
I can post photographs or drawings if needed.

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Chris,
    Option 2 -- insulating the crawl space walls -- is the preferred option. To learn more about insulating a crawl space, see Building an Unvented Crawl Space.

    Brick foundation walls are routinely insulated on the interior. But if the condition of your brickwork is poor, and you have a good reason to think that you'll need access to the walls for future repairs, it's always possible to insulate a crawl space wall on the exterior. The main disadvantage with this approach is that it's more expensive, because it requires excavating the exterior of your house down to the footings.

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