[Greenbuilding] passive haus article

[Topher]

On 8/21/2013 8:50 AM, John F Straube wrote:
> Heat loss through the slab is the same as heat loss through an 
> airtight wall.  If someone told you that the physics are different 
> they are not.

Well, Physics is the same pretty much everywhere except an extremely 
deep gravity well.  But we don't calculate heat loss from elementary 
physics.  Certainly the calculation for heat loss is done differently 
between walls and slabs.  I do agree that the distinction between 
convective and conductive losses is not that simple.

> I recoil at the notion of large amounts of insulation (even 4" of foam 
> is a lot) under the slab because it does not save much energy, unless 
> you use some weird energy model that does not relate to measured sub- 
> slab conditions. 

Being pedantic, I would claim that the energy saved depends not at all 
on /any/ energy model, but rather on reality.  But I am curious what you 
would classify as a 'weird energy model'.  I would also caution readers, 
as always, that the climates and soil conditions vary;  blanket 
assertions are almost always wrong in SOME situation.  We certainly 
don't get 55°F slabs around here.

Thank You Kindly,

Corwyn / Topher Belknap

-- 
Topher Belknap
Green Fret Consulting
Kermit didn't know the half of it...
http://www.GreenFret.com/
topher at greenfret.com

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