[Strawbale] Passive Annual Heat Storage cross post

[Shody Ryon]

> The PAHS )Passive Annual Heat Storage) system
> heats solely by solar. And it uses no electricity
> -no sensors - no fans.

Not in cold/cloudy climates. Since, as it increases
its
heat storage, it exponentially increases the cost of
its
expensive underground insulation, and its heat losses
to the adjacent ground, it is simply impossible for a
PAHS system to store enough heat, in the shorter
summers of the north, via overheating the living
space, for the heating need of the longer, as well
as colder winters. However, even in much milder
climates, it would be more efficient, as well as
more cost effective, to use an efficient, low-mass
sunspace, or other isolated Solar collection, with
an isolated thermal storage. Of course, a house
that is heated by a sunspace and isolated heat
storage, could also be a PAHS house, but the
lower insulation values, fighting a ground temp-
-erature of around 50°F (or less) is not as
effective at keeping a house warm, as simply
using thicker above ground insulation. With
high insulation values, and tight construction,
the slightly higher "outdoor" temperature of
the ground, simply is not al that significant.

PAHS systems are pretty good for moderate
climates, because they do a fairly good job of
cooling during the warm months. They do face
the standard issues of condensation with ground
coupled cooling, but the insulation does tend to
temper that somewhat, which makes it better
than many old-school underground houses,
that have ended up being either under-insulated,
of having no effective cooling at all, because of
little earth mass, and little ventilation. That is a
result of assuming that the earth contact, alone,
without a lot of mass internal to the insulation,
can cool the house during summer, while also
insulating it during the heating season.

. However, there are other very effective ways
to cool a house, even in the deep south. Tony
lives in south central Louisiana, in a house
designed to need no air conditioning. They
are very comfortable. However, even with
their house's excellent performance, I firmly
believe that some isolated thermal mass (in
a thermal loft) would extend the coolness
of the night, further into the warmest
afternoon hours.

A sort of PAHS sytem on steroids is Don
Stephens' AGS system, which uses Solar
collection to charge the earth around the
structure, which effectively stores a lot
more heat, and does not require the
living space to act as the Solar collector,
between the heat and the storage. It sort
of charges the storage from behind,
which is a much better strategy, where
"real" heating is needed.

> For complete solar heating only you should look into
the
> Rocky Mountain Institute's (Amory Lovins) place in
Colorodo.
> They grow bannannas (sp?) in the middle of winter
with no
> supplemental heating. I do not think they consider
computer,
> or human, waste heat as supplemental.

The "elephant in the room", is that the Colorado
location
gets multiple times as much sunlight, per heating
degree day,
during the winter, as many of us get in the MidWest.
Colorado
is a "piece of cake" Solar heating climate. Just
because something
works there is no indication that it will work well
many other places,
or even at all. That system would most likely be an
enormous failure,
in a MidWestern or NorthEastern climate. As for
growing bananas,
they get around double, to as high as four times the
sunlight, in winter,
as the MidWest gets That is not meant as any kind of
slight on Amory
or the Institute. Their buildings are very appropriate
for their extremely
sunny climate. These are just simple weather facts.
What most people
are unaware of, is the vast differences, in climates,
and how they effect
Solar design. Just because it works fairly well in a
sunny arid climate,
is no idication (at all) that it will work well, (or
even at all) in the
cloudy
winters of the MidWest and NorthEast. For example, in
north western
Indiana, in December and January, a south facing,
double glazed, clear
standard glass window will lose more energy than it
will gain. The same
will apply to most of the Low-E windows, which are
specifically designed
to block a lot of Solar gain. So a direct gain Solar
house can require more
winter heating than a standard house (It will still
create poositive heat
for
itself during the milder months). However, a low mass
sunspace, with only
single glazing, on a house in that same climate, will
provide a very high
percentage of the heating, and will use only a small
fraction of the
heat that a standard, or a direct gain house needs.

A few years ago, I wrote an article which does a
pretty
good job of presenting the differences in climates,
and how
much of a mistake it is to assume that just because
something
works in Colorado or New Mexico, that it would also
work
in a different climate. Read the article, starting on
page nine
of the January 2005 issue of -The Energy
Self-Sufficiency
Newsletter-
http://www.rebelwolf.com/essn/ESSN-Jan2005.pdf
There are also charts comparing net energy gain in
BTU/day,
and percentages of Solar heatings, using different
solar heating
strategies, and types of window glass.

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

-LittleHouses-
http://groups.yahoo.com/group/LittleHouses

-WoodGas- Power from Wood.
http://groups.yahoo.com/group/WoodGas

-Refrigerator Alternatives-
http://groups.yahoo.com/group/RefrigeratorAlternatives



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