[Strawbale] water in attic/floor cross post

[Shody Ryon]

Re: Thermal Attic + rain harvesting

From: "Liz Hathway" <liz at ...>

>I am pondering the possibility (strictly theoretical
at the moment)of
> co-ordinating Laren's plans for a sun-space /
thermal attic with Tony's
> success at rainwater harvesting. Would it be
feasible to use a
> rainwater harvesting system with water storage
(cisterns) in the
> thermal attic so that filtered water became the heat
storage as well
> and thus create a situation where year-round usage
of rain water for
> all household needs would be realistic in a cold
winter climate?

Hi Liz;

The standard approach for rainwater catchment in cold
climates,
is to collect during warm weather (even warm days
during winter)
and have enough storage capacity to bridge the period
when every-
-thing is frozen. I will be experimenting with some
approaches for
Solar melting, to allow mid-winter snow melting.
However, there
are inherent problems with drinking melted snow. In
summer, much
of the particulates in the air, are pollen. In winter,
almost all of
it
is pollution. Since percipitation forms around these
particles, this
exacerbates the already bad situation, of snowflakes
containing a lot
less water than raindrops. Every snowflake can be
assumes to
contain a particle of pollution, and it takes a lot
more snowflakes to
make a gallon of water. So, the pollution content of
water from snow,
is many times greater than from rain. It can be
alright for wash water,
but I will sure not be drinking it.

My LittleHouse will have a small cistern (305gal,
~2600lb) down
in my "Solar Crawlspace", where it will effectively
serve as thermal
mass, storing the crawlspace Solar heat, to keep
itself, some plants,
my plumbing, and other things from freezing, as well
as keeping the
underside of the living space floor above freezing,
even when outdoor
temperatures drop way below zero (one of my local
towns holds the
all-time record low temp for the state). I have not
said much about
it, but I think my recent design innovation, of "Solar
Crawlspaces" is
a perfect compliment to the Thermal Attic, BoxWalls,
Solar Source
Heat Pump, and my earlier systems, like my glass and
timber walls,
with their gasketed sealing system. I had never
designed new houses
with crawlspaces until recently. It used to be that
the cost was so
much higher than an insulated slab, but concrete and
rigid insulations
have gotten quite a bit more expensive, and products
like OSB
sub-flooring have brough down the relative costs of
crawlspaces.
The code acceptance of unvented, insulated crawls, is
another
change that allows us to now blur the lines between a
crawlspace
and a basement. The blurred lines allow us to redefine
the space,
and my solution has been to mildly (and low-cost)
Solar heat it.

> We do have periodic thaws.

I believe that we can expect that pattern to continue
and
get worse. With climate warming, comes less stability.
I was
just watchinf a weather forecast, and the next week
will see
days that it does not get above the mid-teens, then
three or
four days later, it will be in the mid forties and
raining. It did
not used to be this way. We used get "permanent"
snowfall
around our Thanksgiving,and we would not see the
ground
until after Easter.

> Not being a pipes, valves, pumps, wires kind of
person
> - how would the rainwater get from the rain gutters
/ filtration
> set-up up to the containers in the attic?

As far as using a cistern/large tank, in the attic, as
heat storage,
it is not ideal. First, the big tank has very little
surface area, and
its walls are thick, so heat transfer is too slow, for
effectively
absorbing the heat that rises from a sunspace. The
reason that
I use small bottles, is that they have a huge surface
area, and
thin walls. They are an excellent heat exchanger. For
instance,
they have over five time the surface area of using 55
gal. drums.
However, larger containers can be used along with the
smaller
ones, for long term heat storage, as long as there are
enough
small ones to provide adequate heat exchange for a
full sunny
day. Then, 24/7, heat can slowly transfer to the
larger container.
However, weight is an issue. That is the main reason
why I like
the cistern, down in the crawlspace. Secondary heat
storage,
below the living space, also serves to sandwich the
living space
between two heated layers. A Thermal Attic totally
eliminates
the heat loss through the living space ceiling. A heat
store, below
can eliminate the heat lossthrough the floor, however,
since down-
-ward heat losses are much smller, and the crawlspace
is not as
easy to super-insulated as a roof, it is not as
effctive as a Thermal
attic. Also, heat below the living space, is crippled
by it location,
because it transfers its heat to the living space, too
easily. There-
-fore, it cannot be heated very much. The attic can
vary up and
down by several tens of degrees, without significantly
effecting the
living space temperatures. But, thermal mass under the
floor can
only change a few degree. Basically, its temperature
will be the
temperature of the living space. So, a huge mass in
that position,
is only capable of storing as much heat as a much
smaller mass,
that is isolated up in the attic. The fact that a
cistern, in the crawl-
-space can set on or down into the ground, also adds
to its
thermal mass, and the temperature stability of the
crawlspace.

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


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