Greentree, dunno what your UDC says about FPSF. It's been in the IBC/IRC since 2000. Just so we are talking apples and apples, your average floating slab in the US is almost surely not a FPSF. (Rare in the U.S., common in Scandanavia.) What distinguishes FPSF from a plain ole SF is insulation spec'ed to keep the ground under it from freezing. It finds its way into the code as an alternative frost protection. (403.3 in 2006 IRC.)

It is acceptable by itself here, however in regard to connecting to conventinal foundations they have added : UDC 21.15 1. "(e) Structures supported on floating slabs or similar shallow foundations may not be physically attached to structures that are supported by footings that extend below the frost line unless an isolation joint is used between the structures. This isolation shall extend for the full height of the structure." (this is the revised code language going into effect)and I would call FPSF similar yet they are pretty vague, as by itself FPSF is addressed and acceptable.
I have more cont. ed this thursday and I will find out WI requirements for sure and post the answer.

Hey Newbiejohn,

I was in your shoes about a year ago.  I wanted to build a well insulated house, but wasn't comfortable with the "newness" of ICF and SIP in my area.  So, I started looking at other options, including the double wall.  I planned to double the exterior walls and use closed cell foam to insulate (you can increase the space between the walls and acheive any "R" you want, and avoid any thermal transfer. 

Then, I found a distributor for ICFs just over the hill (about a mile and a half away).  I went with ICFs and couldn't be happier.  The construction is simple and straightforward, the end result is rock solid.  If I ever build again, I'll use the same methods.  ICF walls with TJs as rafters and insulating directly to the roof deck.   It's a combination that can not be beat IMHO.  

Hey Dug,

What part of the country are you in? Im in a very cold climate, curious your winter heating compared to last housing, what type of heat are you using?

All of this technical talk on the Frost Free Shallow Foundation is making me very nervous....sigh

My home is going to have to be built up roughly 5ft to make grade, whats whats making me the most nervous. I wonder if I just should put in a normal basement foundation.

Here is some quotes i recieved.. Same house plan

109k for ICF just shelled in with roof and siding, windows and doors installed but I would have to pay for them.


109k for full foundation, septic, all fill and groundwork, and home build with double wall, all siding, roofing, windows and doors installed but i have to pay for those.

93k for same except for FPSF

All three homes basically just shelled in but finished on the outside and interior walls rough framed in.

How does one figure out how much overhang one should have on the roof trusses to let in the nice winter sun, but keep it out in the summer ?

Here is a web site with some handy solar tools:

http://susdesign.com/tools.php

I can't imagine why you wouldn't put in the basement since you are so close to one but I'm in tornado country so I'm a little biased towards having someplace to hunker down.

Since you are already talking 5 ft of fill I don't see how a FPSF is any advantage - your foundation has to be on undisturbed earth which will be 5 ft below grade.

John,
The banter between Todd and myself should not apply to your situation, its basically concerns combining a conventional foundation with a FPSF. A FPSF is a great system that works, however run the numbers on a regular basement, usually its pretty cheap square footage.

Jon Clem,

thanks for that link it has TONS of usefull information.