This is off topic and the wrong forum, but with the breadth of skilled trades that participate on this site I figure I can get some good info.
We are adding a bedroom to our mostly unfinished basement. Climate zone 5, bordering on 6 in Iowa. The house is a 2018 modular built into a hill at a roughly 45 degree angle so the basement is walkout with 1 wall entirely exposed and an adjacent wall that is about 50% exposed. The other two are fully backfilled. The basement is entirely poured concrete with 9 foot walls so the exposed basement walls are bare concrete.
Previous owner glued 2” Foamular 150 XPS to all walls and framed 2x4 studwalls inside of that. Both were done subpar, but not bad enough I want to rip it all out and start over. They did not bother to tape/seal any joints of the XPS. That thickness should offer a nominal R10 which I believe is inadequate for our climate zone.
We have not experienced a winter in this house yet so we can’t say how warm the basement will be, but we want to take any necessary steps to keep the bedroom cozy. It will have one wall on the fully exposed side, one on a fully backfilled side, and the other two walls will be interior partition walls. That said, we would like to add more insulation to the two exterior walls and I would like some input to avoid any moldy mistakes that might happen.
Spray foam over the XPS? Fiberglass batt? Mineral wool batt? Cut and cobble more rigid foam in between the stud bays? Fiberglass is most susceptible to mold, mineral wool is better, but both are a breeze to install. I don’t mind cutting and cobbling more foam if that’s the least risky – more XPS or use EPS instead? Regardless of technique I will attempt to seal the existing rigid foam joints and any other air leakage spots I can find (including the joist bays on the sill plate).
The basement is dry and cost is not a concern. Thanks for your input.
We are adding a bedroom to our mostly unfinished basement. Climate zone 5, bordering on 6 in Iowa. The house is a 2018 modular built into a hill at a roughly 45 degree angle so the basement is walkout with 1 wall entirely exposed and an adjacent wall that is about 50% exposed. The other two are fully backfilled. The basement is entirely poured concrete with 9 foot walls so the exposed basement walls are bare concrete.
Previous owner glued 2” Foamular 150 XPS to all walls and framed 2x4 studwalls inside of that. Both were done subpar, but not bad enough I want to rip it all out and start over. They did not bother to tape/seal any joints of the XPS. That thickness should offer a nominal R10 which I believe is inadequate for our climate zone.
We have not experienced a winter in this house yet so we can’t say how warm the basement will be, but we want to take any necessary steps to keep the bedroom cozy. It will have one wall on the fully exposed side, one on a fully backfilled side, and the other two walls will be interior partition walls. That said, we would like to add more insulation to the two exterior walls and I would like some input to avoid any moldy mistakes that might happen.
Spray foam over the XPS? Fiberglass batt? Mineral wool batt? Cut and cobble more rigid foam in between the stud bays? Fiberglass is most susceptible to mold, mineral wool is better, but both are a breeze to install. I don’t mind cutting and cobbling more foam if that’s the least risky – more XPS or use EPS instead? Regardless of technique I will attempt to seal the existing rigid foam joints and any other air leakage spots I can find (including the joist bays on the sill plate).
The basement is dry and cost is not a concern. Thanks for your input.