Double layer r-tech in basement
carlosdanger
| Posted in Energy Efficiency and Durability on
I am about to start insulating my basement in zone 7a. I was planning on using EPS against the foundation with roxul in the stud bays. I found r-tech at home depot. The price for 1″ is $12 while the the price for 1.5″ is $20. I figured it would be worthwhile to do a double layer of 1″ since the price difference between 1.5″ and double 1″ was so small. However, since this product has a facing, I was wondering if it would be problematic to double layer it. Any guidance would be appreciated. Thank you.
Kevin
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Replies
There are no problems created by stacking layers of rigid foam with facers. Stagger the seams of the layers to overlap by at least a foot or so, which would mitigate against performance loss from an shrinkage over time. Taping the seams of the first layer before applying the second makes it more air-tight, and further mitigate against performance loss if the EPS shrinks over a few decades.
Probably not a significant issue, but below writes:
"The research discussed above showed that allowing some moisture vapor to move between the foundation wall and the basement generally leads to dryer systems. "
https://www1.eere.energy.gov/buildings/publications/pdfs/building_america/measure_guide_basement_insul.pdf
This question piggybacks on the basement insulation question stated above:
I have a 100 year old 21" thick fieldstone foundation in region 5 that has cracks and leaks water into the basement in the rainy season. I have read the above manual mentioned above,
https://www1.eere.energy.gov/buildings/publications/pdfs/building_americ...
as well as a fine home building article by Joseph Lstiburek as well and is there a way to use any less expensive product to allow for an interior drain plane such as dimple mat backed up with taped XPS or EPS foam instead of just closed cell spf? The cost of 3" spf is around $5 and will price me out of being able to do my home. Any ideas of water control with insulation to allow for a conditioned basement would be greatly appreciated.
"The research discussed above showed that allowing some moisture vapor to move between the foundation wall and the basement generally leads to dryer systems. "
This is kind of what I was wondering about. Is this not a major concern or is there a better alternative to what I have planned. I thought using the r-tech would be the more environmental, cost-effective and convenient alternative but perhaps there is a wiser choice? Thanks again.
Kevin
It's probably worth finding a local EPS manufacturer and getting a quote. It's a bit of a hassle vs. the online Home Depot catalog, but I expect you'd get better prices.
Thanks. I´ll look into that. Do you think it is worthwhile to do a double layer in the rim joist also, or would it be enough to put one later of 1¨ eps and fill the rest with Roxul. Thanks again.