Insulated Shallow Foundation


  #1  
Old 02-06-06, 06:09 PM
ollie
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Insulated Shallow Foundation

Where in the early stages of adding an addition to our home. The area where we are building has a 72" frost line. In doing research about foundations I came across information about "insulated shallow foundations". They look interesting and a nice saving over a regular foundation. I've been able to get a lot of information but nothing about the nuts and bolts of building one. Does anyone have experence with this type of foundation or know where I can info on how they are designed.
Thanks
Ollie
 
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Old 02-06-06, 09:04 PM
M
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Frost Protected Shallow Foundations

http://www.huduser.org/Publications/PDF/FPSFguide.pdf

The HUD publication above will get you started.

Next place to stop is the reference section of your local library for a copy of the International Residential Code 2003 which is Pennsylvania's building code and has a detailed explanation begiining in section R403.3

My question is:

WHERE in Pennsylvania is the frost depth at 72"?!!

I have never seen a jurisidiction in Pa with a frost depth of more than 48 before.

That said, frost protected shallow foundations can only work under certain conditions such as:

--- maintaining the year round temperature of the structure that will have the FPSF at 64F

----cannot be connected to a basement or crawlspace unless that area is also kept at a minimum year round temperature of at least 64F

---- The structure can meet minimum state energy code requirements using a FPSF.

The last one is probably the most difficult one because since FPSF are constructed slab-on-grade, they are difficult to get to meet energy requirements for the structure as a whole.

I've tried to design several FPSF for customers in your state and was never able to given the increase in insulation requirements and decrease in window and door spaces needed to use them.

You might look into a closed-crawl space design instead, which although a bit more cost to install, is the most energy efficient design going today.
 
  #3  
Old 02-07-06, 04:22 AM
ollie
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I'm in PA now but the house were adding to is in Northern NY. I do beleive that 72" is a little much but you can't fight "city hall".
Our plan is to use a closed and conditioned crawl space. I was trying to find out if a crawl space will work with this type of foundation. Every thing I've read so far shows a slab which I'm trying to avoid. I beleive NY is under the IRC 2003 and I'll get a copy. I have the hud pub. I was just looking for more info. I think the hardest part will be finding a contractor who knows this type of construction.
Thank for the input
Ollie
 
  #4  
Old 02-08-06, 08:51 AM
M
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Ok. so the house just may have a frost depth of 72" for parts of NY....

But a frost protected shallow foundation has to be built on a slab. Closed crawlspaces must have their footings extend below the frost line.

You could build a frost protected shallow foundation on a slab but have a closed crawlspace above grade, but the savings are marginal at best with such a configuration.

And because the wall insulation for a closed crawlspace has to extend down the walls and at least 2 feet below the frost level, and where the floor is above the frost level, the insulation has to continue on top of the floor the same 2 foot distance below the frost level only horizontally...

You will have at least 8feet of insulation on top of the slab floor coming in toward the center of the crawlspace from every exposed wall with such a configuration...

This could make such an arrangement very impractical....

Don't know what else to suggest, but it appears a conventional footer with a closed crawl space will be the best alternative.

I've yet to be able to see a frost protected shallow foundation work for extremely cold climates...
 
 

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