How to insulate an overhang in zone 3?
user-2310254
| Posted in Energy Efficiency and Durability on
I have a small overhang on a second floor bedroom that extends over the front porch. I had planned to complete seal the overhang to isolate it from the rest of the structure and add R30 open cell between the warm and cold area. Another contractor has suggests that I should not seal this space. He would instead include this area in the building envelope while also spraying R30 open cell on the bottom of the subfloor. So should I create a sealed space or integrate it into the envelope?
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Replies
Steven,
What type of "area" is this? Is it part of the bedroom (warm in winter and conditioned in summer)? Or is it an unused attic or kneewall area?
If it is useful, conditioned space, the insulation needs to be located in such a way that the space is included in the conditioned area of the home. If it is an unused attic, you can locate the insulation in such a way that it is outside of the conditioned area of the home.
Hi Martin:
The trusses on the second floor create an entry cover for the main entrance to the house. The subfloor in this overhang area is part of a second floor bedroom. The bottom of the overhang will be finished out with a tongue and groove board. But now that I think about it, these boards should go over OSB so we can tape the OSB seams and then apply the tongue and groove.
So if I follow these steps, where is the best place to spray the foam? Along the perimeter and against the subfloor, or along the perimeter and against the OSB sheathing?
Steven,
I'm not sure what you mean by "along the perimeter."
If I understand you correctly, a section of the bedroom floor is above an unheated entry or porch. If this is indeed the case, it is of course necessary to insulate the exposed section of the floor. You might find this article useful: How to Insulate a Cold Floor.
After you have insulated the exposed floor, you will also need to insulate the bedroom walls, of course, and the bedroom ceiling. You need to pay attention to air barrier continuity and thermal barrier continuity at all of the junction points: where an insulated floor meets an insulated wall, and where an insulated wall meets an insulated ceiling (whether sloping or flat).
Sorry for the incoherent question. Your link was very helpful, and I now feel we are on the right track.