[Greenbuilding] R-value of crushed stone under slab

Alan Abrams alan at abramsdesignbuild.com
Mon Dec 7 18:24:08 CST 2015


Frank, the stone was under 9" of geo foam @ R-4.2, supporting a 4" slab..

still, according to PHPP, there is a lot of impact to the gross modeled
result from decoupling the assembly from the subsoil. FWIW, the gravel fill
was also encased in vertical
insulation. So the R-value of the stone may not be trivial...

-aa

Alan Abrams

*certified professional building designer, AIBDcertified passive house
consultant, PHIUS*
*certified passive house builder, PHIUS*
cell     202-437-8583
alan at abramsdesignbuild.com
HELICON WORKS *Achitecture and Education*
<http://www.heliconworks.com/index2.html>

On Mon, Dec 7, 2015 at 7:03 PM, Frank Tettemer <frank at livingsol.com> wrote:

> I would consider the 24" of gravel as a steady, 24/7 heat loss.  In fact,
> in a colder climate, (like Eastern Ontario, Canada), there would be little
> consideration of trying to heat that gravel. Any heat going into it from
> the house would continue traveling down and out, and the heat added to the
> stone would never return to the house. Unless you opened all the windowsand
> doors to quickly chill the place. Then for a short while, the cool stones
> would give offtheir relative heat to the room.
>
> In other words, dee-coupling from the stones, with at least R-25
> insulation, would be a Good Idea.  If you were a Passiv Haus enthusiast,
> you would insulate with R-45 or more, to prevent heat loss to those stones.
>
> Frank Tettemer
> Living Sol ~ Building and Design
> www.livingsol.com
> 613 756 3884
>
>
>
>
> On 07/12/2015 5:26 PM, Norbert Senf wrote:
>
>> Right, I was only addressing the "heat capacity expressed as MJ(m^3K)"
>> part of the question. R value of gravel is a look-up value............N
>>
>>
>> On Mon, Dec 7, 2015 at 2:42 PM, Nick Pine <nick_pine at verizon.net <mailto:
>> nick_pine at verizon.net>> wrote:
>>
>>
>>     Norbert Senf <norbert.senf at gmail.com
>>     <mailto:norbert.senf at gmail.com>> writes:
>>
>>         ... the specific heat would be .14 MJ/m3-K
>>
>>
>>     I'm afraid that has nothing to do with R-value.
>>
>>     Nick
>>
>>
>>
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>>
>> --
>> Norbert Senf
>> Masonry Stove Builders
>> 25 Brouse Road, RR 5
>> Shawville Québec J0X 2Y0
>> 819.647.5092
>> www.heatkit.com <http://www.heatkit.com>
>>
>>
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