[Strawbale] Frost Heave

[Robert Tom]

--- In SB-r-us at yahoogroups.com, "Hank Carr" <hank at ...> wrote:

[reams of cut & pasted attempts at obfuscation <snipped>]

> Figure 3. FPSF Heat Flow Diagram for a Heated Building withOptional  
> Floor Insulation
> It looks like an insulated slab to me.


There's a vast difference between "a diagram" (to show how heat flows)  
and  actual "design procedures".

The first is a hand-waving thing like an Art History course. It doesn't  
actually show you how to do anything.

To cut to the chase, this thread started because of the following:

================Quoted Material =====================
On Tue, 13 Nov 2007 07:08:02 -0500, Speireag Alden <speireag at gmail.com>
quoting a declaration that

> Hank Carr wrote:
>
>> With rubble trench and slab foundations the building should be heated
>> in the winter whether you are living in it or not to keep the ground  
>> under the building thawed and to prevent heaving and cracking.
=============End of quoted material =================


For actual design of superinsulated foundations, as pointed out to you  
(Hank) in the past,the Simplified Design Method (which relies upon heat  
loss through the foundation to raise the frost line) cannot be used.

One has to assume that the building is essentially unheated and for that,  
one has to use the Detailed Design Method for Unheated Buildings. But  
don't take my word for it. Check for yourself.

Just in case Hank misses the relevance of this again...

Unheated building = building which is not heated, therefore no attempt to  
keep earth under building thawed via heat loss through foundation  = same  
as superinsulated shallow foundation

And key to the "detailed design for unheated foundations"  (and hence  
insulated shallow foundations which minimise heat loss to the earth in/on  
which they sit)  is the same key requirement that the building codes have  
for shallow foundations and slabs on grade (in heating climates).

And guess what that is ? (Hint: It's not the insulation.)

It's the requirement that the substrate not be susceptible to frost  
action. (The clause in Section 4 which Hank was supposed to make note of  
when sent back to the OBC which he cited/interpretted inappropriately)

And just what is this magical, mysterious "stuff" that is not susceptible  
to frost action ?
(And which will not be described explicitly in the codes)

Surprise, surprise! It's exactly the "stuff" that's used to construct RTFs.

(ie Coarse granular material with no fines to clog up the interstitial  
voids,  all properly drained to ensure that water does not accumulate in  
those voids... thereby removing a critical ingredient (ie water) in the  
equation for frost heave to occur.)

Go figure. Eh ?

-- 
=== * ===
Rob Tom
Kanata, Ontario, Canada
< A r c h i L o g i c  at chaffY a h o o  dot  c a >
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