[Strawbale] water in attic cross post 3

[Shody Ryon]

Re: Attic heat storage & etc.

From: "john felch" <lat38col36 at ...>

> I have been reading with interest your ideas on
attic heat
> storage in PET bottles. It sounds like a good idea.
Recently
> you alluded to the need for a large quantity of
bottles in the
> attic to make this work . My question - how many
bottles
> per 1000 sq ft of floor space would be required,

Hi John;

None. Floor area has nothing to do with it. The
storage
is calculated based on calculations for the sunspace
heat
gain (based on your specific climate), the surface
areas of
the bottles, the mass of the water, heat loss of the
house,
the likelihood of cloudy days, the personal desire for
a
goal percentage of Solar heating, and the availability
of
appropriate space for the storage. But, not floor
area.

> How far apart would each bottle be from it's mates,

Against, above, and below them. They usually
set in racks, in layers, like a big heat exchange
filter,
for the warm air to flow down through as it is cooled.
Sometimes, if there is already plenty of heat exchange
surface to absorb the heat, but more mass is needed,
while space is limited, some 55 gallon drums can also
be used. I also have another storage/heat exchange
medium, so water can be pumped through a radiant
distribution system.

> and how much would this all weigh. if, as I believe
you said,
> we are talking thousands of pounds in a relatively
small area
> of floor,

About 4-1/2 lbs per bottle, including racks to hold
them.
It is usually very typical of standard floor or roof
live loads,
about half as much as the snow loads I have to deal
with
in northern Michigan. It definitely adds some weight
but
not much, in house load terms. I was just working on
the
structure of a house, and I had to add $100 in
additional
joists, so it is generally no big deal. Basically,
there is no
additional cost, and usually savings, because there is
no
need for an expensive central heating system.

> what structural requirements would there be for the
> ceiling/floor of the storage area.

Strong enough to support it. Pretty much the same
as a second story. It all depends on the house. In
some
cases the heat sink can set above a stairway, or the
wall
between the sunspace and the living space, or in some
other location with fairly short spans. In some cases
the
racks, that hold the bottles, can span between bearing
points, as their own structure, and no structural
floor is
required, to hold them. Every house is different. But,
basically the building cost should be around the same,
as conventional, or less.

> Have you ever installed such a system in a new
house,

I am just beginning to use two liter PET plastic soft
drink
bottles. However, I have been using the same basic
heat
storages, with other types of water containers in the
attic
since the mid 1980s. I have done at least a dozen new
houses that way. Two-liter bottles were simply not yet
available to use back then. There were one gallon HDPE
bottles, like milk and cider jugs, but they were not
as dur-
-able as PET plastic. Their lids could not be trusted,
and
they also did not exchange heat as well, because the
plastic
was thicker. 55Gallon drums do not have nearly as fast
a
heat exchange, and also do not fit into small spaces.

> what was the overall cost of the installation,

Comparable to conventional construction. Generally,
any additional costs are made up for, by the
elimination
of an elaborate conventional central heating system.
For
instance, there is no reason to have natural gas, or
pro-
-pane coming to the house, or the equipment to burn
it.
Quite consistently the owner contracted houses were
appraised (increase in value over the improved lot)
for mortgage, after construction loan, at right around
twice what they cost to build.

> and what percentage of heating did it achieve?

About a 90% reduction from what a comparable
sized conventional house uses. However, virtually
all of the houses I did back in the Solar craze of the
70s and 80s (well over a hundred) ended up being
insulated with fiberglass, even though I stressed
using
cellulose. We also were forced to vent the cathedral
ceilings, and insulate them with fiberglass, which
resulted in about half as much ceiling Rvalue as with
dense pack cellulose, and a third or more less wall
Rvalue. I was using enough sunspace glazing to get
virtually 100% Solar heating, but the houses were
never insulated well enough for it, in the cold and
very cloudy Michigan winters. I have learned a
lot since then, and so it is generally easier now.

The storage is just one component, and on its own,
does not determine the percentage of Solar heating.
I find it to be the best storage i know of, in several
ways.

1) It absorbs the heat fast. (lots of heat exchange
surface)
2) It is relatively light weight (water stores 6.4
time as much
heat as concrete or stone, per weight.
3) It is extremely low-cost (water and bottles are
usually free)
4) It is out of the way (takes up little or no living
area, in the attic)
5) It requires no fan to store the heat (Warm air
rises)
6) It is silent
7)It requires not electronic controls to store the
heat.
8) It stores the heat away from the glazing, and its
heat loss
9) It requires no back-flow dampers
10) It also works to power stack effect summer venting
11) It stores coolness for summer cooling
12) It isolates the heat so the living space does not
overheat
13) It allows the use of a programmable thermostat for
controlling heat distribution to the living space, and
lowering the house temp at night and while away.
14) It can be used as a heat/cool source for a
low-cost
heat pump back system.
15) The heat sink has no moving parts
16) Zero maintenance.
17) Can sometimes serve as dehumidifier in summer.
18) It is easy to install
19) If the house catches fire, it will provide
million of BTUs of cooling, to control and
possibly even put out the fire, as the bottles
will melt and release their water, at under
200°F. There evaporative cooling BTU
potential may be as much as double the
BTUs of the house structure burning.

> If this is proprietary information I understand.

No, it is not. My system has developed into being
uniquely mine, but the general way it works, is not
totally unique. Besides, I am interested in changing
the way all houses are built, not keeping it all a
secret. My personal goal is to be able to sell some
stock plans, but also DVDs of various aspects of
the buildings, so that owner builders and other
designers will be able to follow a step of step
procedure, and use basic comstruction details,
to design their own systems.

> I would like to include such a system in my
> retirement house design .

I think that is a good idea. I expect to have pictures
from the workshop, in about a month. Hopefully, there
will be future workshops, in other parts of the
country.
I intend to fully monitor the performance of my little
demo structure, here in the toughest Dec-Jan Solar
heating climate, in the lower 49 states.

-Laren Corie-


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