[Greenbuilding] Crawlspace foam insulation -- how much?

[Leslie Moyer]

And why would this be preferable to just spraying the joists, too?

On 6/12/15 2:17 PM, Alan Abrams wrote:
> Hi Leslie
>
> somehow I don't like the idea. I assume the insulation contractor is 
> proposing to apply foam to the underside of the floor sheathing. If 
> that is the case, there is the possibility of the exposed portion of 
> the joists getting below dew point, and becoming saturated with 
> condensed water vapor. IIRC, Joe Lstiburek has some really ugly photos 
> of this condition.
>
> my preference (at a minimum) would be to seal and insulate the 
> perimeter of the floor cavity with caulk and batts, and apply a smart 
> membrane (like MemBrain) to the underside of the joists, carefully 
> lapped and taped, and then some rigid mineral fiber insulation under 
> that. Fire resistant, mold resistant, thermal bridge resistant, and 
> semi permeable. The crawlspace can then behave or misbehave as it 
> pleases, without impact on IAQ
>
> -aa
>
> Alan Abrams*
> */certified professional building designer, AIBD
> certified passive house consultant, PHIUS/
> /certified passive house builder, PHIUS//
> /cell 202-437-8583
> alan at abramsdesignbuild.com <mailto:alan at abramsdesignbuild.com>
> HELICON WORKS /Achitecture and Education/ 
> <http://www.heliconworks.com/index2.html>
>
> On Fri, Jun 12, 2015 at 2:55 PM, Leslie Moyer <unschooler at lrec.org 
> <mailto:unschooler at lrec.org>> wrote:
>
>     Yeah, well, I considered that option first and was ridiculed for
>     that on this list several months ago. My crawl space is tight (for
>     humans), but well-ventilated, so I'm going to go with this option
>     as I think it is the most practical.
>
>     --Leslie
>
>     On 6/12/15 1:18 PM, Frank Tettemer wrote:
>>     Hi Leslie,
>>
>>     You may want to re-consider the idea of foaming the floor in a
>>     crawl space. My concerns would be that the foam would act too
>>     well as a vapour barrier, and you may have moisture/mildew
>>     problems down the road in the crawl space. I AM in Canada, so
>>     your geographic climate might create different problems than here.
>>
>>     I always design any neccessary crawl spaces as a definite part of
>>     the conditioned space of the home. That means insulating the
>>     walls and the floor of the crawl space, and leaving the floor as
>>     a vapour-open plane, as well as including the crawl space in the
>>     heating design. This avoids condensation trouble, by keeping the
>>     air warm and dry.
>>
>>     Frank
>>
>>     Frank Tettemer
>>     Living Sol ~ Building and Design
>>     www.livingsol.com <http://www.livingsol.com>
>>     613 756 3884
>>
>>
>>     On 12/06/2015 2:02 PM, Leslie Moyer wrote:
>>>     I am in NE Oklahoma.  I'm in the process of getting estimates
>>>     for crawlspace insulation in the floor joists--closed cell foam.
>>>     My crawl space is dry now that we've fixed some plumbing
>>>     problems, but I'm having some cupping issues with some wood
>>>     flooring and part of the fiberglass batts that were originally
>>>     in the house when we bought it were taken out over time for this
>>>     and that. Anyway--closed cell foam seems to be the best solution.
>>>
>>>     The first guy who came this morning wants to quote me 1.5" foam,
>>>     though said he would quote 2" if that's what I really want,
>>>     saying that would be enough for "Canada".  I understand about
>>>     the benefits of air sealing, but I was still thinking I would
>>>     need more inches of foam according to what I've read on R-value
>>>     & this area.  Thoughts?
>>>
>>>     -- 
>>>     *Leslie Moyer*
>>>
>>>
>>>
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>>
>
>
>     -- 
>     *Leslie Moyer*
>     Email: unschooler at lrec.org <mailto:unschooler at lrec.org>
>     Phone: (918) 772-6150
>     Cell: (918) 633-8820
>
>     Sustainable Tahlequah
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>
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