Zone 6 walls
I’m in zone 6 northeast PA, building a 38×24 garage/shop next door to the house. 2×6 framing, with 12” raised heel trusses. 13’ ceilings on stem-wall foundation with 5” slab inside and slab has pex tubing for in-floor heat. There is about 14” of block wall exposed above slab inside, and grade outside.
At this point I am framed and sheathed with plywood, and asphalt shingle roof is on with ridge vent. Plan to 14” of cellulose in attic and fill stud bays too. In order to try to make things easy I only have 1 man door and 1 garage door (10×12). The idea was to have more insulated wall, and less penetrations.
Going forward I seem to be stuck figuring out a good wall assembly. From from plywood out. Plan to air tight WRB at plywood either full adhered membrane or liquid applied. Then I had always planned to rigid exterior, 3” on walls above foundation, and 2” on foundation into the ground. So my questions are…
Is it worth it to exterior insulation at all, and if so if I airtight WRB at plywood, do still tape and seal rigid insulation? Then other than furring strips and vinyl siding what goes on top of rigid insulation?
Any guidance would be greatly appreciated
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Replies
Hi Rob.
I won't speculate on whether it is worth adding exterior rigid foam to the garage or not. That depends on what your goals are, how much you'll actually be conditioning the space, etc.
I certainly think you should do a good job air sealing, even though the overhead door will be a big energy/comfort penalty. Would you consider insulated and weather sealed carriage doors instead? I have seen some installed that seemed much tighter than a common garage door, though I can't prove that statement with numbers from a blower door test.
If you do install airtight sheathing and flash your windows and other penetrations at the sheathing plane, it is still a good idea to stagger and tape the foam seams. Then it's the rainscreen assembly details and siding.
How are the slab and stem walls insulated?
Hey Brian Thanks,
Hey Brian Thanks,
“Would you consider insulated and weather sealed carriage doors instead?”
Probably not, between the additional expense and complication, but I had thought about it earlier.
OK, so I tape the rigid foam seams, I wasn’t sure, the foundation is uninsulated, but the slab has 2” of XPS under and at edges.