[Strawbale] Hot water storage concept - insulation

[Joaquin Brintrup]

> 
> On Mar 16, 2008, at 18:25, Tom Oswald wrote:
> 
> > Hi,
> > We are working out ways to store heat in
> water-mass for home hot water 
> > and limited/back-up space heating.  We plan to
> heat the mass by 
> > passive solar, fire-box, and possibly surplus PV. 
> We are considering 
> > using a concrete septic tank to hold the water in,
> even though it may 
> > not be the most green material to use.  We are
> considering placing the 
> > tank outside the foundation, under a deck, on the
> earth.  We want to 
> > avoid using foam insulation around and under the
> tank as it is not a 
> > green material.  We are thinking about using saw
> dust but are 
> > concerned about it getting wet.  We are seeking
> suggestions on how to 
> > do this most efficiently and most ecologically.
> 
> I would consider using foam insulation before I
> would use concrete.   
> But first, I would move the thing inside.  Heat loss
> inside is heat 
> gain (though it drops your hot water max
> temperature).  I can't think 
> of a way to insulate a tank with sawdust outside. 
> Plastic bags might 
> work for a while, until they broke.  And there is no
> way they will work 
> under the tank.  If I could figure out a way, I
> would use cellulose 
> insulation instead.
> 
> If you want to to give some specifics in the way of
> R-value, 
> dimensions, etc. I can run some heat loss numbers
> for you.
> 
> Thank You Kindly,
> 
> Corwyn

Hi, if you can place the tank above earth, you can
isolate it with straw bales, like a house (you can use
 thicker walls to improve insulation) 

Now, under the earth, you could still use straw bales,
if they are absolutely water proof. (breathability is
not a problem here). Some time ago I was playing with
the idea of using straw bales covered with plastic, or
something like a huge "tetra box", so you can be able
to use in under the earth in contact with humidity.
Never tried it, though, and since you need plastic it
is also not 100% green solution.

Other possibility would be to use a 2 tank system: a
larger one with straw bales, and a smaller one inside
for the water. That way the bales stay dry and the
water isolated. 

Leting the straw bales aside, what about pumice? if
you can get some, it will make a good insulation.

Just crazy ideas, hope it helps.

Joaquin Brintrup


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