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Insulating behind built in cabinets

utkdoc | Posted in General Questions on

After playing with a FLIR camera, I discovered that the built in cabinets in our laundry room are open to the exterior and uninsulated. There is one on each side of the wall about 7′ tall and around 8′ in length.  The room is kneewell type construction. I don’t know what was there previously as these were put in by the former homeowner. As best I can tell the remainder of the room is insulated, but where the cabinets were installed there is no insulation behind them. We’re talking 1/4″ melamine in most areas with zero air sealing that is open to the soffit/kneewell exterior underneath the roof. Obviously this room has quite a temperature delta from the rest of the upstairs and somewhat smells like an attic space at times.

There is an access behind one of the cabinets on both sides allowing you to crawl behind so I went in only to see all of the nooks and crannies with light shining through WIDE open to our conditioned space. It looks like this may have been a small storage area. There are no studs where the kneewell is vertically (i.e where you would normally expect them) and I think was originally framed to be this way. My question is, what is the best way of insulating behind these cabinets that will also air seal? I thought about XPS and taping the seams but not sure if that is the best- the surface behind is not entirely flat and has some protrusions but I think I can work around those and still do a lot better than the R 0.0001 from the 1/4″ of wood I have now. The other issue with this is the boards will probably need to be broken down into 1/3 sections in order to fit through the access panel.
Spray foaming I think I would end up with more product waste than I would actually use. 
Without studs, I don’t think I would be able to secure batt insulation nor would I be able to do any air sealing.

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  1. walta100 | | #1

    From your description I am having a hard time imaging what you are describing.

    How are your other wall insulated?

    Is their any reason not to use the same materials to insulate this wall?

    Most laundry room cabinets are prebuilt and can be remover with a few screws. It seems like it would be much easier to work without the cabinet installed.

    All foam is expensive, ungreen and a fire hazard so it is best avoided if possible.

    Could you post a few photos?


  2. utkdoc | | #2

    It is a bit hard to take a decent photo from the inside, but the outside photo should give you a better idea. These are cabinets on both sides.

    edit: I am not able to upload photos -- I will give it a try when I am home tonight

  3. Expert Member
    BILL WICHERS | | #3

    If you have a sort of studdless wall (so just a sheet of plywood or something?), then rigid foam is probably your only option short of spray foam. I'd use sheets of polyiso here, with seams taped. You could glue it in place. XPS would work too, but would provide less R value per unit thickness. Air sealing should be relatively easy if you can work with fulls sheets of insulation behind the cabinets, since you could tape all the seams and then just seal the perimeter with caulk and/or canned foam.


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