Thick Stud Wall Insulation
One of our exterior walls is balloon framed and engineered with an insane number of 2×10 LVLs to hold our ridge beam (pic attached). This wood combined with a lot of U .25 glass has me thinking about the whole wall insulation value. New build — Climate Zone 6.
On the one hand, since we have a 2×10 plate, the area outside the center that holds the ridge beam will have a lot of batt insulation and be continuous, since studs will be offset to fit the 2×10 plate. We could do R38 with rockwool here. On the other hand, I’m worried about this highly dense section of wood and glass.
Thinking about exterior CI foam, it might not be worth the effort, since such a small surface area would end up being covered with the foam where it was needed, and that affects the whole exterior plane.
Curious what folks think. Maybe just focus on the other walls and the whole house and let this one be what it is — a wall with a lot of glass and a lot of engineered lumber in the middle of it.
Thanks,
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Replies
There's not much you could do about the glass, aside from stepping up to full 1-3/8" triple pane IGUs, which can get you a U value that ends up around R8 or so.
For those thick walls with staggered studs, exterior rigid foam won't buy you as much as it would with a normal studwall since you won't have the thermal bridging issue using staggered studs. You really only have that one really thick wood column section to deal with. I would consider "boxing out" that one spot and putting some rigid foam over ONLY THE COLUMN portion of the wall. I'm not sure what your exterior is going to look like from that pic, but if the glass runs up to either side of that central column, boxing out that column a bit so that you can squeeze in some 2-3" or so of polyiso probably won't have much visual impact but will greatly increase your R value in that area.
BTW, you could save some money using fiberglass in that wall instead of mineral wool since you have so much depth to work with. You'd sacrifice a bit of R value, but you'd have a significant monetary savings and should still be able to get around R34 worth of insulation in that wall.
Bill
Thanks Bill -- boxing out the one section in the middle would look nice and solve the issue. Seems straightforward but I hadn't thought of it. Thanks,