[Greenbuilding] Unifoam vs Plastispan

[John Straube]

Oh I believe you Lynelle.  I get this kind of thing all the time
JFS: “But your design load for the soil is 2500 psf, why do I need 3600 psf insulation?”Soils engineer  “Because”

> On Oct 3, 2017, at 7:27 PM, Lynelle Hamilton <lynelle at lahamilton.com> wrote:
> 
> Hi John, 
> 
> The engineer is very specific about the 30psi under the edge.  He initially wanted it under the slab as well, but did switch that spec. 
> 
> On 2017-10-03 6:59 PM, John Straube wrote:
>> I am not sure what is special about your slab, but standard XPS (25 psi max) has been used for decades.  Hence, EPS with more than 25 psi seems odd anywhere except where a concentrated load occurs.  Remember, 25 psi is 3500 psf, which is more than most soils can take. But to answer part of the question I have use PlastiFab EPS of wide range of strengths successfully for a long time, and have no experience with Uniform.
>> Of course insulating with R-35 under slab seems very odd… the result of bizarre interior conditions or bizarre calculation methods?
>> 
>> 
>>> On Oct 3, 2017, at 6:24 PM, Lynelle Hamilton <lynelle at lahamilton.com>
>>>  wrote:
>>> 
>>> I am insulating under a floating pad. The engineer has specified 25psi under the slab and 30 psi on outer edges.   I've been looking at two products: Unifoam 25/30 and Plastifab 25/30. Aiming for R35 under the slab.  Price differential is significant (Unifoam is nearly $3000 more) for the house.  
>>> 
>>> Has anyone had experience with either product? From the specs, Unifoam appears to absorb less water and has less deflection, but both are within the ASTM spec for the issue. 
>>> 
>>> Many thanks for any insights!
>>> 
>>> Lynelle Hamilton
>>> 
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Dr John F Straube, P.Eng.
jfstraube at uwaterloo.ca
www.JohnStraube.com