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Insulating the floor of 500 sq ft addition on skirted piers (1950s house)

marleyandbowie | Posted in General Questions on

Hi everyone,

I recently purchased a funky 1850 sq ft mid-century home in SW NH. It sits on a cinder block foundation, combination of basement and crawlspaces. At some point, probably in the 50s-70s, they added a 500sq ft rectangle on piers that serves as the master bathroom and bedroom suite. The piers are skirted with what looks like asbestos fireboard or something of the like, that runs from the bottom of the walls down roughly 10″ below the earth line, as to almost give the appearance of a normal foundation. Running under the subfloors of this approximately 6-12″ “crawlspace” are old ductwork, plumbing and electrical. It smells moldy, has rodents, and there is loose fill fiberglass and cellulose insulation everywhere. It’s pretty much a disaster and whoever thought this was a good idea must have been smoking crack. Access to this space can be gained by cutting into a non-weight bearing CMU wall through the basement, and/or by digging down around the perimeter, removing the skirting and trying to crawl below.

How do I deal with this? It would be a shame to demolish because the structure is in decent shape and the bathroom is pretty nice. I’d love to find a way to preserve it without spending a fortune, otherwise I’ll just tear it down and start again.

My thinking is that I gain access however necessary – through the basement and through the exterior, remove all the old sheet metal ductwork, remove all the old insulation, remove the skirting boards because they neither allow airflow nor air seal the space enough to make it a conditioned space, and replace that skirting with breathable lattice.

Assuming that is the correct path, how do I insulate the floors of the bedroom and bathroom and how do I prevent the plumbing from freezing? 

Photos: https://imgur.com/a/zAGgRX4

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