[Greenbuilding] Passive solar home--concrete overlay re thermal mass

[Alan Abrams]

one consideration here is that capping an existing slab in a passive solar
system that presently works "extremely well"-- that is, adding more
mass--is not necessarily more better.  more mass will retard the cycle of
heating and cooling, changing the character of thermal comfort.  if the cap
is thin enough, maybe it won't be noticed--but this is all quantifiable.

it all raises many questions--about the climate, about the substrate under
the slab, about the details of the envelope of the house--all factors that
come into play in this decision.  maybe there is not much insulation under
the slab, so that removing it provides the opportunity to install it.  if
there is adequate insulation under the slab, then maybe a thin cap is in
order.

on the subject of thermal mass and heat transfer, I think RT's earlier
reply was definitive.  thermal mass is simply a function of density or
specific gravity, and an acrylic admixture and/or thin film of bonding
compound between original and new slabs would neither change the density of
the slab or retard conductive heat exchange between the two in any
significant way.

some time ago on this list serve, back in the pleistocene era, IIRC, there
was a discussion on high strength, super thin slabs, akin to ferro-cement
boat hulls--which might have application here.  someone with even more time
than I have to waste could look it up.

AA

Alan Abrams*
**certified professional building designer, AIBD
certified passive house consultant, PHIUS*
*certified passive house builder, PHIUS**
*Abrams Design Build LLC
*sustainable design for intentional living*
6411 Orchard Avenue Suite 102
Takoma Park, MD 20912
office  301-270-NET- ZERO (301-270-6380)
fax      301-270-1466
cell     202-437-8583
alan at abramsdesignbuild.com
www.abramsdesignbuild.com
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