[Greenbuilding] Crawlspace

[ErgoDesk]

*Sometimes the best solution to problems, such as Moisture is to remove the
problem material. Wood Rots but we still use it as a major Construction
Material instead of removing it and replacing it for a better more suitable
one. Not a band aid but a total replacement, a material that is better in
many ways. *
*
*
*Today's wood is not yesterdays wood and should be avoided not only for our
health but for well being during Climate Change, where Water and Moisture
may become a real big problem. Poly is to short an answer, Expanded
Polystyrene is a better one because it not only has little affect with
Water, it also Insulates and has a very, very long lifespan. More on EPS
floating raft and othe foundations information at: *
http://styrohomeconstruction.yolasite.com




On Sat, Jun 2, 2012 at 6:22 PM, nick pine <nick at early.com> wrote:

> Stuart Fix <sfix at renubuildings.com> wrote:
>
>  Humidity within the crawlspace should be controlled via poly on the ground
>>
>
> That would seem to invite condensation from warm moist house air in a cold
> climate, without a vapor barrier below the floor and insulation below that.
>
>  and proper ventilation (either passive screens or active fan/humidistat).
>>
>
> Passive screens would seem to invite condensation from warm moist outdoor
> summertime air. So would automatic foundation vents that are open at 70
> F... http://www.amazon.com/AIR-**VENT-RABL-AUTO-FOUNDATION/dp/**B000IJWOV6<http://www.amazon.com/AIR-VENT-RABL-AUTO-FOUNDATION/dp/B000IJWOV6>How about a smart vent, ie a fan with a differential absolute humidity
> control... http://www.smartvent.biz/ ?
>
> If a simple humidistat turns on a fan to move outdoor air through a
> crawlspace when the crawlspace RH is too high, say higher than 60%, what
> prevents the fan from moving warm moist outdoor summertime air through the
> crawlspace, with condensation?
>
>  Eli's comment:
>> The issue I am trying to understand is how to maintain in a ventilated
>> crawlspace to be warmer than dew point.  The vapor barrier on the ground
>> only stops ground sources of humidity.  A high standard thermal barrier in
>> the floor keeps the ac cooling from cooling the bottom surface.  However,
>> the shading will keep the crawlspace cooler than outside.  Could this cause
>> condensation?
>>
>
>  Response...
>>
>
>  The only way to STOP condensation from occurring, in the situation you've
>> described, would be to heat the crawlspace, or to ventilate the space at a
>> high enough rate that it maintains the same conditions as outdoors. Both
>> are likely a waste of energy.
>>
>
> The second way seems especially wasteful, since maintaining exactly the
> same conditions as outdoors requires infinite fanpower :-)
>
> Gary BIs <gary at builditsolar.com> wrote:
>
>  I converted my crawl space to a conditioned space as discussed in this:
>> http://www.builditsolar.com/**Projects/Conservation/**
>> Insulation/CrawlSpace29238.pdf<http://www.builditsolar.com/Projects/Conservation/Insulation/CrawlSpace29238.pdf>
>>
>
> Do they suggest a vapor barrier under the floor? They say "Air sealing
> between the house and crawlspace is less critical" with crawlspace wall
> insulation.
>
>  I put two layers of poly on the dirt and sealed it around the edges and
>> at seams. I blocked all the vents and I foam can sealed all around the rim
>> joist. Then insulated the crawl space walls with polyiso foam board with
>> tape  on the seams... its been about 6 years, and its worked fine for me.
>> The crawl space feels dry.  I do live in a dry climate (SW MT)...
>>
>
> Amen?
>
> Nick
>
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