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Converted Porch Crawl Space Sealing and Insulation

hustle | Posted in Green Building Techniques on


I have a second question about my 1906 house in Essex County, NJ (Zone 4A, borders 5A).

At some point, the 7′ by 15′ back porch was converted to a bathroom and mudroom. The walls and ceiling/roof appear to have been insulated with fiberglass batts, but the floor/foundation was not insulated.

The porch rests on the original rusticated cinder block piers. The spaces between the piers were infilled with modern CMU, with two small air vents, creating a vented crawl space. Access is via a hopper window from the main basement. The crawl space has a dirt floor, slightly above grade. No moisture problems are apparent. The crawl space isn’t conditioned.

I’d like a warmer floor. Am I better off installing a moisture barrier on the floor and sealing and insulating the CMU walls, creating an unvented crawl space, or sealing and insulating between/under the floor joists themselves, and leaving the remaining crawl space as is?

There are domestic water and waste pipes running in the crawl space. They have frozen in the past. I imagine creating an unvented crawl space would go some way to preventing this from happening again, though I also intend to heat-trace and insulate the pipes.

Thanks again,

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  1. GBA Editor
    Martin Holladay | | #1

    If you have had problems with frozen pipes, the answer is obvious: You need to turn the crawl space into a sealed, conditioned crawl space by insulating the walls. Here is a link to an article that will tell you what you need to do: Building an Unvented Crawl Space.

    -- Martin Holladay

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