[Strawbale] water in attic cross post 4

[Shody Ryon]

Re: Low cost thermal mass

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

> In my 1500 sq ft retirement home, using approx 166
gal
> of water storage per 100 sq ft I come up with
approx.
> 2500 galons of water or 20,750 lbs. of mass located
in
> the attic.

That is a huge heat storage. Why do you want so
much water? What would you use as a collector?
What is the total UA (heat loss per °F, per hour)
of the house? What is the location/climate?

> Have you ever considered what effect that weight
> would have on a structure in a strong earthquake?

Yes, of course. It is a fairly small load. But, I have
never considered using that much water, even on
houses I designed that were over twice that size.

What you discribe is only 13.83lb/ft² over 1500ft²
Let me give you an idea of how small that load
actually
is, in house design terms. It is less than 35% of the
minimum code design load of a bedroom floor, less
than 28% of the minimum code design load of a
primary living space floor, and only a sixth of the
minimum code roof design load in my area.

It is also only 69% of the minimum design live load
of an attic floor (with limited storage). In other
words,
in terms of typical, standard housing design loads, it
is minor, and would usually require no more than
standard construction It is a standard load for a
standard, run of the mill house. But, it is over twice
as much as an actual heat storage would weigh in
one of my houses.

Minimum design loads for 1500ft² of:
(compared to your 20,750 lb)

Primary living area: total load 75,000 lb. (3.6 times
greater)
Sleeping areas: 60,000 lb (2.9 times greater)
Roof: (IN, OH, IL, etc) (cathedral ceiling) 67,500 lb
(3.25 times greater)
Attic (limited storage) 45,000 lb (2.2 times greater)

Now, after you see what real loads are, ask yourself
(to quote you) "Have you ever considered what effect
that
weight would have on a structure in a strong
earthquake?"

It sounds to me like you had no idea what standard
design loads actually are. That lack of knowledge
can make the relatively light load of a heat storage
seem like a lot, especially when you exagerate it
by 100%, like you did. But, it is not a big load.

Now to get real, about this. I would expect that
a 1500 ft² house that I designed, for most climates,
would have less than 10,000 lbs of water storage,
Maybe a lot less ((based on available Solar gain,
and heat loss calculations. It has nothing to do
with house square footage) That weighs equal to
the minimum code design live load of a standard
13ft by 19ft floor area.. (a sixth the area of a
1500ft² house)

However, I usually design my heat storages to put
little
or no load on the attic floor, and to be supported by
a
wall(s) that bears down to a footing. In areas at high
risk for earthquakes, there are special design
consider-
-ations, for all houses, just as there are in
hurricane areas,
or any unusually demanding situation. But, there is
nothing
about a heat storage that is different from other
loads,
because it simply is not a large load.

Warning: Just because it is not a large load for a
floor
area, does not mean that it could not be a very large
load, if that load were not spread out, or not bearing
on a point that could handle the load. Designing such
a
system requires care, and an understanding of
structure.

-Laren Corie-


      ____________________________________________________________________________________
Be a better friend, newshound, and 
know-it-all with Yahoo! Mobile.  Try it now.  http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ