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Basement insulation detail around utilities & metal framing

Brad Stoppenhagen | Posted in General Questions on

I’m remodeling a basement that includes building a new framed wall inside the foundation.  The home is located in Zone 4 (Cincinnati, OH).  The current plan is to place 2″ faced EPS on the walls followed by framing and mineral wool insulation.  Basically, I’m building as outlined in the article https://www.greenbuildingadvisor.com/article/the-stay-dry-no-mold-finished-basement.

My question is how to handle the foam detail around plumbing that is held tight against the wall.  I have a 3″ PVC pipe that runs horizontally across most of the wall.  I’m trying to get away from moving the pipe due to loss of space.  How much of an issue concern is there if I terminate the foam above/below the pipe and spray foam the gap?

Given the cost of wood lumber I’m considering using metal studs for the wall framing.  I know there is a lot of concern about the thermal performance of walls with metal framing.  I’m a bit less worried about the reduced whole wall R-value as the assembly will far exceed what is elsewhere in the house.  That said, I there is a better way, I’m all for it.  In another thread, Dana suggests:

“to use steel for the studwall, use shallow steel FURRING (less than 1.5″ deep, not something that fully penetrates the rock wool layer, or even half way. A standard steel 2×4 is 4.0″ deep, so using standard 7/8″ hat-channel furring instead of studs to trap stacked batts up against the foam will yield something over R13 for the steel + rock wool assembly using standard 2×4 steel top/bottom channels. That reduces the full penetrating steel to just the top & bottom channels. A further improvement would be to use narrower channels for the hat furring to eliminate even those thermal bridges.” (https://www.greenbuildingadvisor.com/question/10-inch-thick-cement-basement-walls-insulation-vapor-barrier-question#comment-177170)

Using hat channels is an interesting approach/  While the walls are not load bearing, is there any structural concern for hanging items off the wall (e.g. shelves, TV’s, etc) or would the hat channels be sufficient?

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Replies

  1. Expert Member
    Zephyr7 | | #1

    I can't quite visualize the use of hat channel to accomodate batts, but I can tell you that hat channel is plenty strong enough to hang stuff on the wall if the channel itself is anchored the way it's supposed to be (periodic fasteners, not just top and bottom). I have a commerical project right now, that will hopefully be done soon (it's a doctor's office and the X ray install guys are way behind schedule), with 5/8" drywall hung on hat channel against a block wall. It's an interior wall, so no insualtion. They have a TV going on that wall for their waiting area. There are no issues with the structure, but any electrical will need to be in the very shallow "pancake" boxes to be able to fit.

    You can get steel studs in all kinds of dimensions. There are narrow ones not much different in size from a stick of unistrut, for example. You can also get them in many different gauges, so you can get thicker steel if you want a stronger wall. Any commerical supplier of steel studs can help you here -- this is very common stuff on commerical jobs.

    Regarding thermal bridging, just put all you insulation in in the form of rigid foam and don't worry about it. Thermal bridging of any type of stud is only an issue when the insulation is BETWEEN the studs. If you put continuous rigid foam between the studs and the foundation wall, you'll have no issues with thermal bridging and your choice of studs no longer matters in terms of the wall's thermal performance. There is no need to use batts if you use all rigid foam.

    Bill

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