[Greenbuilding] Hot tub building

[Kathy Cochran]

So.................What if I used Cedar strips, sort of like a wine barrel.
And if I took up Corwyn on his idea of using sheeps wool for insulation,
how would I keep it from getting wet, or anyway, how would I attach it to
the wall of the water vessel?  (I would think I would want to keep it from
getting wet.............)So .my layers would be.............from inside
out.............Cedar or redwood...........then sheeps' wool in whatever
"container" they would need to stay dry and stable), then possibly whatever
PVC or PEX tubing might be required to circulate water, and create a drain,
and maybe some (as yet undetermined) electrical access for lights and heat,
then shore up the outside with native rocks in mortar.  Are we getting
there?

I know that once the tub is filled, the wood will swell, but shouldn't
there be something behind it.......like black plastic - to hold it all in? 
Maybe the sheeps wool should be contained in black plastic bags?  Or would
that affect the insulation qualities that it would have without the
plastic?  

I am well aware of the concept of "heating the whole outdoors"...........so
a lid could be built with additional redwood or cedar strips - to hold it
all in.  Insulated with sheeps wool, then another layer of wood, to
cover.............this could get heavy.............!

I'm really appreciating your input.................

Kathy



> [Original Message]
> From: Keith Winston <keith at earthsunenergy.com>
> To: <greenbuilding at listserv.repp.org>
> Date: 7/9/2007 8:02:33 PM
> Subject: [Greenbuilding] Hot tub building
>
> Hi Kathy,
>
> First, concrete is not strong in tension, but only in compression. So 
> unless you have a very solid "form" that's going to remain, simply 
> lining it with concrete is unlikely to work well. Also, I'd agree with 
> Corwyin that you want to insulate it. Also, are you thinking you are 
> going to fill it with groundwater (55F) and heat it to hot tub temp 
> (105F) and then dump it out afterwards? There's a reason hot tubs have 
> covers, pumps, and filters. If you have a 600 gallon tank, for example, 
> that's roughly 4800 lbs of water, and 240,000 Btu to heat it up 
> initially, plus whatever it takes to keep it hot, losing heat to the 
> surrounding air, earth, and immersed bodies. Figure a decent solar 
> collector might gather 30,000 Btu/day, you can see why hot tubs are 
> energy hogs, and why you'd want to insulate it, keep it covered, and 
> pump/filter the water.
>
> Of course, the smaller the cheaper (money and energy-wise). I was 
> figuring 5' diameter and 4' deep, with nothing removed for bodies or 
> seats. You might be able to make it 1/2 that, for two people, if you 
> shape it right... Maybe even less.
>
> Keith
>
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