[Strawbale] Sub Floor Radiant Heating

[Speireag Alden]

On 2007, Nov 28, at 15:22, Shody Ryon wrote:

> I was wondering about thermal storage (TS) in this
> way, because dry earth is a good thermal mass (TM)
> medium which generally available to land owners, why
> not make a large area a TS area, the larger the
> better.

     The larger your mass, the more insulation you will need to  
enclose it.  If you can't enclose it, then you must accept huge  
losses as part of the design, which is why in an AGS system Don  
Stephens says that you can expect to get back only about 20-30% of  
your input.

     That's why you shouldn't power an AGS or PAHS system with  
anything but renewable, non-polluting input.  Hait says you can do it  
with just passive solar. Stephens recommends active input.

> Can earth be used to store cool and does the earth
> need to be dry like for storing heat?

     Yes, the earth can be used to store coolness as well as heat.   
Just not at the same time in the same earth.  :)

     The earth does not need to be dry.  In fact, the heat capacity  
of wet earth is obviously higher than dry earth.  However, if there  
is water moving through the earth, it will suck the temperature  
differential away.  So you can't have moving water.  Thus, the  
umbrella which is the essential part of the design.  During a  
discussion with Don, I once mentioned that if I had to omit either  
the waterproof layer or the insulation, I would omit the insulation.   
He agreed.  Shedding that cold water and snow melt elsewhere is more  
important.

> I have not full explored "air through pipes in the
> ground" systems, but some people have had mold
> problems in the pipes. I think this has mainly been
> for cooling “earth tubes” but I do not know, because I
> became interested in the thermal loft system using low
> thermal mass in the house driven by thermal siphoning
> and a solar assisted heat pump.

     I think the mold issue can be addressed by using perforated  
pipe.  That way the soil bacteria can set up a normal, balanced  
ecology.  However, you have to design such that you exclude soil gas.

     It's not easy being green.

> Water can be used instead of air through tubes. There
> is a draw back to this but I can't think of it right
> now.

     If the pipe breaks, you're screwed.

     If an air pipe has a leak, no biggie.

     On the other hand, a water pipe can transport orders of  
magnitude more heat than an air pipe.

-Speireag.