Insulation old shop
Hello I’m remodeling my shop in zone 5a in MN I have reframed the ceiling joist to 2×8 have purling strips and radiant barrier installed. Will be blowing cellulose in attic and 1/2 Sheetrock. Walls are 2×6 dimensional lumber 24 on center. and exterior sheeting is tongue and groove with felt paper and some old mdf style siding and the front has new lp smart side siding. Wanting to air seal the walls and insulate the best I can . Have removed the windows and have an insulated garage door. I’m looking at installing 2 inch eps in the walls with fiberglass r13 batt and a smart vapor retarder. Will have purling strips on wall as well to install 1/2 rock. Is this my best bang for buck to air seal the walls and get my best r value without having to worry about any potential condensation or rot issues. I have a high efficiency ducted mini split installed in the shop as well. I’m not intrested in installing exterior insulation at the moment as my budget has gotten out of hand with this remodel would like to in the future though. Maybe in a couple years. Buikding is pretty airtight to my suprise have have been sealing up and gaps or cracks in the sheeting if I have found any. I believe it was built in the 50s
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
I'm also in MN, but I'm 6A. You must be down in the driftless area in the SE corner.
If you don't want to touch the outside I would spend your time detailing your smart vapor retarder (something like Intello) as the air barrier on both the walls and ceiling. Careful taping at all overlaps is key. I'm assuming that there is a concrete slab. If it is in good condition, you can lap the vapor retarder onto the floor slightly and press it into a bead of sealant.
If it were me, I would not bother with the EPS foam. Cutting it to fit into each stud bay is a pain, and it doesn't have drastically more R per inch than batt insulation. I would take that money and use it to switch to something that holds its shape better than fiberglass like Rockwool or Timber Batt. You'll get a more complete fill of the cavity.
Plus, you will be eliminating drying potential, which is going to be important. Since you have floor that likely has no vapor barrier or insulation, you will have a fairly large moisture load. I would be hesitant to add any foam to your assembly because it is really great at preventing outward drying.
You may end up running a dehumidifier as well. Not having plastic and insulation under a slab was not a problem when the building was leaky and all wood. But it could become one with a tighter building.
Yes in the sw corner of mn. Ye I’m sure it has no vapor barrier under slab. I have been wondering if that was going to be an issue as well . So probably just seal up the old tng best I can to keep any air filtration out that I can? And fill the cavities with a good insulation and if I want to insulate further go to an exterior insulation later on?
That would be the route I would choose. The key would be to detail that smart vapor barrier so that it is also your air barrier by taping the seams and sealing it to the floor. If you do that, you have moved your air barrier from the outside wall to the inside wall and you don't need to worry too much about sealing the T&G unless there are big gaps that would cause significant amounts of air to wash through the insulation.
Hey Ben and Zach,
FYI, I recently took a MN contractor continuing education class put on by Don Sivigny from DOLI, he said the state is going to keep the southern half of Minnesota in climate zone 6A. (No 5a for the SE corner.) The comment he made was so that there wasn't confusion about a 3rd zone, which would be new to Minnesota. I do believe we will eventually see a larger piece of MN in 5A, but it won't be before the 2030's when the next version of the climate zone map is released.
Randy