[Strawbale] concrete floor vs. wood floor

[Shody Ryon]

--- Robert Tom <ArchiLogic at yahoo.ca> wrote:

> Shody Ryon qi4u at yahoo.com wrote:
> 
> > A tromb (sp) wall has solar energy input often
> every 24 hrs.

What I meant to say they get a few hours sun light in
24 hr cycles, not that they are exposed to sunlight 24
hrs a day. I do not remember why I said that but I was
likely promoting the idea of thermal storage. The
reason i said often was because if a storm darkens the
sky enough, there may be insufficient light to make
heat, so a lot of thermal storage can be helpful in
this situation.

<snip> 
> the descriptor "poor" would be inappropriate because
> it would consume more  
> material and cost more than a concrete or earthen
> floor.

An earthen floor would probably be better for the
environment and would probably cost less. I wish more
people would consider using it.

I do not know about the above statement regarding
concrete vs wood, perhaps it is correct.
This is part of Laren's post which I assume would
still be true below grade, could you explain why it
isn't. I do not think the concrete price is for an
above grade pour:

Laren:
A far as cost, raising the floor up gives me a covered
storage work area, for less cost than any other way.
Concrete and XPS Foam insulation have gotten so
expensive lately, that it is more economical to build
a wood frame floor, and fill it with cellulose. For
example, in Maine, in January, when outdoor air
gets the coldest, and averages about 15°F, the deep
ground temp may be around 42°F, but you have to
deal with the ground temp near the surface, so it is
more like the average, which would be around 28°.
If we assume a floor temperature of about 65°, we
can look at a 1000ft² R20 concrete floor heat loss,
in January of about (65-28) x24x31x1000/20 =
1,376,000BTU. With 2x12s and cellulose, we will
have about (65-15) x24x31x1000/35.4 =
1,051,000BTU. (about 24% less). The XPS foam
insulation will cost about $2000, and is not very
"green". The cellulose will cost about $300, and
is very "green". The wood floor or concrete will
cost about the same in materials. Maybe the wood
might run an additional $500, since it needs to be
closed in underneath. Again............wood "green"
concrete...."not green" So the savings is in a range
around $1000, and you get a floor that is insulated
a third better, when you need it the most. The
foundation will cost about the same. In milder
months of the heating season, the slab will suck
even more heat (relatively) from the house. Even
an insulated slab is a heat loss. That can be a good
thing where cooling is the priority, but in the north,
where heating is a greater concern, a slab is a big
additional heating load.

-Laren Corie-
Natural Solar Building Designs, Since 1975
www.LarenCorie.com

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