Sealed crawlspace double insulated stem wall?
I am in the final days of deciding how I am going to configure the foundation waterproofing and drainage system and who is going to do the work for my house build in zone 4a. I will have a reasonably short crawl space with the tallest stem wall being around 50″ of brick & block and no more than 24″ of the stem wall will be below the finished grade in any location on the house.
I have received quotes from several companies ranging from $5500 – $18k and all are recommending different materials and scopes of work. The that seems the most reasonable given my situation proposes to coat the brick with a liquid waterproofing membrane, and then apply an insulated fiberglass drainboard on top of that. I think the drainboard is really only there to protect the membrane from the gravel drain and not really for any useful energy saving purpose. My question / concern with that approach is that I will also be insulting the inside of the crawlpace with R10 or R15 foam and sealing the crawlspace and I am not sure how a brick/cmu wall that is fully insulated on the inside and partially insulated on the outside will behave.
Are there any issues with this approach? Would I be better off given the shallow craw space depth to just use the fabric of the “fabric / gravel drain burrito” to protect the liquid membrane?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part