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maurice richter Posted: Feb 20, 2011 01:54 PM	crawl space - sides or under of floor My question today has been bugging me for quite some time. On various home improvement advice shows, it is usually mentioned to insulate the walls of the crawlspace. But I know that the ground becomes a 50-55degree heat sink (in central Indiana down to a certain depth it is always 50-55). I know a bit about Manual J, a house slab is measured for heat loss as a perimeter lineal feet. But yet for in-slab radiant heating, there should be insulation put down before the slab is poured so that the radiant heat does not go down to the ground. If the sides of a crawlspace were insulated, then we are talking about a delta-T of 20 (70 living - 50 ground). If the floor in insulated, it becomes delta-T of 70* (70 living - 0* oat.) So my limited thinking is that closed cell foam on the underside of the floor would be good. If there are reports or printed data I should read, please point me to them! Thanks! Maurice
Posted: Feb 21, 2011 06:10 AM	I have my crawlspace encapsulated by basement systems and I beleive the current building science which is to seal the crawlspace and turn it into a conditioned space. The last thing I need to do is to sprayfoam the rim joist area so there is zero air leakage into that space. The temperature will stabilize as my supply ducts are in the crawl. In my case I do not see the need to sprayfoam the floor and since there is a vapor barrier on the floor and walls and doing the floor would add another vapor barrier which is not what I want.
maurice richter Posted: Feb 21, 2011 08:32 PM	NJ, Do you have more descriptions of the encapsulated crawl? Is it just some plastic sheets? are they sealed to each other? Does it get punctured if someone crawls on it? I know the climate in Trenton/Princeton area, are you in a harsher climate of NJ? (I'm probably showing my ignorance...) But then again, why not insualtion between the conditioned crawl and dirt?
quentin Posted: Feb 22, 2011 09:37 AM	If possible we prefer to spray the floor for the added benifits of a stronger floor and not having the local code officials who hate sealed crawls complaining. If they have a cost issue we lay down 10mil plastic to 6in up the sides and overlap it with foam sealing everything including the joists and bandboards. We still try to get them to allow us to at least so a flash over the HVAC ducts to help more and both systems seem to work here in Ohio.
ChrisIgna Posted: Feb 22, 2011 02:43 PM	crawlspace encapsulated by basement systems are very expensive systems that look pretty when you take pictures. They are more of a moisture managment system than an insulating system. The systen uses a 20 mil plastic liner much like a pool liner. This is to seal the water vapor from enteing the crawl. The liner goes up the wall and stops short of the plate/rim joist. In most cases Fiberglass is installed in the floor and rim joist. This system looks pretty but does nothing to control heat/coolonr loss. We have done crawls both way underside floor and Wall. You have to look at the best soultion for the customer. In my findings the prices come out almost the same if you are using a proper vapor barrier on the floor like a 10-15 mil plastic. When to do side walls-- if you have Hvac Duct in this space or want to use it as semi-condationed storage. It is the same as doing an atiic when to do the underside of the roof deck Vs attic floor. It is the same cheap vs effective. We as sprayfoam contractors should be doing the proper scope of work not just the most cost effective.
maurice richter Posted: Mar 25, 2011 06:43 PM	New twist on the question/problem! I was in the crawl, moving dirt so I could re-route a return duct. 100+ year old, brick foundation, each "room" has a separate foundation. So when I moved dirt at an interior foundation, I found it was very shallow. Bottom line is an exterior foundation is only 16" deep. In our area, a fencepost needs to be at least 32" deep, and a post for a pole barn needs to be 4 feet deep. (I will found out what masonry new house foundation requirements are.) Im not sure what kind of expert to ask! I suspect that if I where to stop heat loss to the crawl space, it could allow the dirt under the 16" foundation to frost-heave!
Posted: Mar 26, 2011 08:38 AM	sounds like you need an engineer not an insulator
maurice richter Posted: Mar 26, 2011 10:28 PM	I still want to get the walls foamed this summer. As for below the walls+floor, an engineer sounds good...
maurice richter Posted: Mar 30, 2011 08:26 PM	Amazing what one can find on the internet! (And if its on the internet it MUST be true!) But seriously, I found "FPSF" Frost Protected Shallow Foundation. Might be my solution.
angus mcdougald Posted: Mar 30, 2011 08:38 PM	spray the outside of the foundation.....

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maurice richter

Posted: Feb 20, 2011 01:54 PM

crawl space - sides or under of floor

My question today has been bugging me for quite some time. On various home improvement advice shows, it is usually mentioned to insulate the walls of the crawlspace. But I know that the ground becomes a 50-55degree heat sink (in central Indiana down to a certain depth it is always 50-55*). I know a bit about Manual J, a house slab is measured for heat loss as a perimeter lineal feet. But yet for in-slab radiant heating, there should be insulation put down before the slab is poured so that the radiant heat does not go down to the ground.

If the sides of a crawlspace were insulated, then we are talking about a delta-T of 20* (70 living - 50 ground). If the floor in insulated, it becomes delta-T of 70* (70 living - 0* oat.)

So my limited thinking is that closed cell foam on the underside of the floor would be good.

If there are reports or printed data I should read, please point me to them!

Thanks!
Maurice

Posted: Feb 21, 2011 06:10 AM

I have my crawlspace encapsulated by basement systems and I beleive the current building science which is to seal the crawlspace and turn it into a conditioned space.

The last thing I need to do is to sprayfoam the rim joist area so there is zero air leakage into that space. The temperature will stabilize as my supply ducts are in the crawl.

In my case I do not see the need to sprayfoam the floor and since there is a vapor barrier on the floor and walls and doing the floor would add another vapor barrier which is not what I want.

maurice richter

Posted: Feb 21, 2011 08:32 PM

NJ, Do you have more descriptions of the encapsulated crawl? Is it just some plastic sheets? are they sealed to each other? Does it get punctured if someone crawls on it? I know the climate in Trenton/Princeton area, are you in a harsher climate of NJ? (I'm probably showing my ignorance...)

But then again, why not insualtion between the conditioned crawl and dirt?

quentin

Posted: Feb 22, 2011 09:37 AM

If possible we prefer to spray the floor for the added benifits of a stronger floor and not having the local code officials who hate sealed crawls complaining. If they have a cost issue we lay down 10mil plastic to 6in up the sides and overlap it with foam sealing everything including the joists and bandboards. We still try to get them to allow us to at least so a flash over the HVAC ducts to help more and both systems seem to work here in Ohio.

ChrisIgna

Posted: Feb 22, 2011 02:43 PM

crawlspace encapsulated by basement systems are very expensive systems that look pretty when you take pictures. They are more of a moisture managment system than an insulating system.
The systen uses a 20 mil plastic liner much like a pool liner. This is to seal the water vapor from enteing the crawl. The liner goes up the wall and stops short of the plate/rim joist. In most cases Fiberglass is installed in the floor and rim joist.
This system looks pretty but does nothing to control heat/coolonr loss.
We have done crawls both way underside floor and Wall. You have to look at the best soultion for the customer. In my findings the prices come out almost the same if you are using a proper vapor barrier on the floor like a 10-15 mil plastic.
When to do side walls-- if you have Hvac Duct in this space or want to use it as semi-condationed storage.
It is the same as doing an atiic when to do the underside of the roof deck Vs attic floor. It is the same cheap vs effective. We as sprayfoam contractors should be doing the proper scope of work not just the most cost effective.

maurice richter

Posted: Mar 25, 2011 06:43 PM

New twist on the question/problem! I was in the crawl, moving dirt so I could re-route a return duct. 100+ year old, brick foundation, each "room" has a separate foundation. So when I moved dirt at an interior foundation, I found it was very shallow. Bottom line is an exterior foundation is only 16" deep. In our area, a fencepost needs to be at least 32" deep, and a post for a pole barn needs to be 4 feet deep. (I will found out what masonry new house foundation requirements are.)

Im not sure what kind of expert to ask! I suspect that if I where to stop heat loss to the crawl space, it could allow the dirt under the 16" foundation to frost-heave!

Posted: Mar 26, 2011 08:38 AM

sounds like you need an engineer
not an insulator

maurice richter

Posted: Mar 26, 2011 10:28 PM

I still want to get the walls foamed this summer. As for below the walls+floor, an engineer sounds good...

maurice richter

Posted: Mar 30, 2011 08:26 PM

Amazing what one can find on the internet! (And if its on the internet it MUST be true!)

But seriously, I found "FPSF" Frost Protected Shallow Foundation. Might be my solution.

angus mcdougald

Posted: Mar 30, 2011 08:38 PM

spray the outside of the foundation.....

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