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Community and Q&A

Window in crawl space?

BJHuffine | Posted in General Questions on

So my initial thoughts are no, because I feel like there are too many opportunities for air to leak around them.  However, I thought I’d ask the community in case I’m over-reacting.  Basically, due to the building site, we chose to pour our foundation.  They’ve done a great job with it too.  The back side is much higher than the front, so they are “daylighting” the back.  In other words, the back is 4 ft high along the living space section compared to the back of the garage wall which is just over 9 ft.  The 5 ft will be made up in wood framing.  The crawl space will be tall along the back side and likely at regular ceiling height.  We’re putting gravel in it to level the back half so that the space will be someone usable for storage.  With the wood framing portion, it’s also tempting to put one or two fixed windows in there to allow some natural day light in.  It might not make for much use at first, but if we decide to pour a pad in there, it would make for a neat and small shop area (or other space if the wife decides :))  However, we’re encapsulating the crawl space, which means it’s very import to either, or both, effectively insulate the foundation walls (whether concrete portion or wood framing) and flooring from underneath.  I fear this could compromise this and have the potential for air to leak through.  We do want this to be a tight house and are even sealing the sill plate, etc, to help ensure this.  So am I not thinking about this right?  Or is placing a small fixed window or two really of no consequence?

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  1. Expert Member


    The only consequence is a small energy penalty, but probably well worth it if you intend to use the space later.

    1. BJHuffine | | #2

      Do you think there's enough typical insulation value in today's windows and sealing around the framing to not be problematic? Or maybe there should be some things worth implementing if we do? I actually do like the idea, but don't want to add problems that'll have to be dealt with down the road if that's likely.

      1. Expert Member
        MALCOLM TAYLOR | | #4


        A window in a conditioned crawlspace is exactly like one anywhere else in the house. You should have no more of less problems than with one in a living room.

        There is an energy penalty because windows make poor walls, and it will need to be air-sealed and flashed just as you would if it were upstairs.

        1. BJHuffine | | #5

          Thanks Malcolm

  2. Andrew_C | | #3

    Which direction would the windows face? And how far off the ground would the windows be?
    My guess is that if it's a big space and it's dry because you encapsulated it and put insulation down underneath the slab (you're planning for that, right?), someone is going to want to use that space. So I'd probably put in a couple of windows.

    Out of curiousity, are you putting in a full-sized door that has exterior egress? Make it a wide door so there's plenty of room to get stuff in and out of your wife's workshop. ;)

    1. BJHuffine | | #6

      The windows would be facing South, so they would not be getting any direct sun light. Realistically, they should be able to be placed anywhere in the range of 5' to 8'. Just so that we can get through this build, I think we'll add the slab for this part later unless it looks reasonable to do now. We've ran into so much rock, the footers have put us over budget right off the bat, despite our test digs to prepare ahead of time. But when we do, insulation under it is definitely the thought here! The gravel bed will already be there.

      I do hope to put in a full sized door. Running through the numbers it looks like it should work, but with the staggered height of the foundation walls, I can see it being close too. Building on solid rock (we're on a mountain) has presented us with some interesting challenges.

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