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-   -   Insulating Crawl Space (http://www.diychatroom.com/f103/insulating-crawl-space-157056/)

beengone 09-17-2012 08:36 AM

Insulating Crawl Space
 
Now that I'm moving forward slowly with the walls and attic, I'd like to figure out the best way to insulate my crawl space. My house is a 1870s era in central/northern Michigan. The basement is common for Michigan in that it starts as a 8' stone walls and a poured floor, continues to an area with stone walls and a partially poured floor (plan to pour the rest eventually), and finishes with a newer block wall with a large knock-out that turns into an all-dirt crawl space sloping up to be about 2' or so high. The foundation is stone and I have some filling of holes to do in the mortar, but not too much. There are no vents and they've partially covered an old exterior door with a closet, but the lower 1/4-1/3 is exposed in the crawl space. It's just an old all-wood panel door, so no real R value.

In the summer, we have pretty high humidity into the 80%s or so. This time of year, it hovers between 50-70%.

Unfortunately, I pretty much can't pour a floor in the crawl pace due to not being able to remove enough dirt safely without fear of disrupting the foundation and floor supports. Also, the water comes in from this side and there is a lot of plumbing at this end of the house.

Am I best off removing all the sharp and large rocks from the crawl space and putting down plastic vapor barrier on the floor? Should that also go up the walls? If so, do I just vent through it? I'm afraid I'll have to vent above the mud plate as I don't think I'll be able to poke through the stone.

What about insulation? Can I put unfaced batts on the walls? should those extend all the way up to the floor or just up the stone to the mud plate? What R value should I choose? Or, is it worth my while to get foam insulation sprayed in? If so, how do I handle vents?

Thanks.

Windows on Wash 09-17-2012 08:47 AM

How is the drainage and water management around the foundation?

Do you get standing water?

Fairview 09-17-2012 10:27 AM

Quote:

Originally Posted by Windows on Wash (Post 1011526)
How is the drainage and water management around the foundation?

Do you get standing water?

---------------------------------------------------------------
I'm glad to see this most important question ask first. Since the structure has been there since 1870 I'm suspecting the answer is no.

I realize all the supposedly intelligent people from fine home building sites, this old house etc. etc. would recommend what you are contemplating with the insulation and plastic but back up a step or two and ask yourself why this building is still standing without those modern and supposed better building techniques. In my opinion you are getting puckered up to screw it up with moisture problems you don't have at present. Let the old house breathe.

beengone 09-17-2012 10:52 AM

Don't know why I didn't answer that in the OP. no standing water since we've been here and no signs of any ever, including that there is no sump. Humidity is the only problem.

The insulation would be to
Make the house more efficient and keep the floor in the rooms over that space warmer. I don't have to keep out humidity if I seal that end off from the rest of the basement, but fear mold problems if I don't have some kind of air movement. Am I off-base?

Insulation is my higher priority.

Windows on Wash 09-17-2012 01:13 PM

Theoretically you could insulated the crawlspace walls and convert it to a conditioned spaced.

That being said, as Fairview eluded to, it might be better to just insulate the under floor (i.e. the joists) and leave the walls alone. If the joists are properly insulated and sealed up, there won't be any humidity issues that will affect the structured joists.

A vapor barrier across the floor is never a bad idea. That can be sealed to the bottom of the crawl space wall.

beengone 09-17-2012 02:05 PM

Quote:

Originally Posted by Windows on Wash (Post 1011723)
Theoretically you could insulated the crawlspace walls and convert it to a conditioned spaced.

That being said, as Fairview eluded to, it might be better to just insulate the under floor (i.e. the joists) and leave the walls alone. If the joists are properly insulated and sealed up, there won't be any humidity issues that will affect the structured joists.

A vapor barrier across the floor is never a bad idea. That can be sealed to the bottom of the crawl space wall.

That leaves the humidity issue into the rest of the basement unless I seal that end off, which means a door and a bit of plastic. IS that a better bet? Just wall it off from the rest of the basement and open it up in the winter so the pipes don't freeze? The pipes run under the joists.

Windows on Wash 09-17-2012 02:11 PM

Sounds like a good candidate for a conditioned crawl them.

There are a ton of threads on here about that and Building Science.com does have quite a few options and case studies on the approach.

beengone 09-17-2012 06:37 PM

Think that sounds better than just blocking it off in the summer and opening it to the basement in winter?


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