[Strawbale] Sub Floor Radiant Heating

[Speireag Alden]

On 2007, Nov 27, at 14:11, Ilan Ungar wrote:

> I was asking about slab thickness because I imagine I would want  
> the heat to
> be smooth with little low and high peaks.

     Do you mean smooth over time, or smooth across the surface of  
the floor?

     If you mean the second, you just make sure that the pipe in the  
floor isn't spaced too far apart.

     If you mean the first, then yes, more mass will result in a  
larger lag time and more thermal momentum.  However, if this will be  
an elevated building, then that mass will also cost you in support  
structure.

     Here's an intriguing possibility for an elevated building:  put  
it up on pilings, but leave space and access underneath so that you  
can put 55-gallon drums (or similar containers) of water underneath.   
If you elevate it 30 inches or more, you could have the drums  
upright, and have an awful lot of them.  Plumb them together, and run  
the pipe through them.  Insulate under and around them.  Using water  
as your heat storage medium, you'll have tremendous capacity (far,  
far more than a thick slab), you'll be able to replace leaky ones,  
and it will all be protected and hidden under the house.

> The article also mentions the high cost of this system, around  
> $14,000.
> Solar panels and tanks are not that expensive here, is it the PEX  
> that makes
> this system so expensive?

     I wonder.  I hear prices of $8,000 and up routinely quoted for  
radiant floor systems.  I put mine in for the cost of the pipe, the  
fittings, and a brass recirculating pump.  About $1,000.  Now, I have  
only one zone, and I turn it on and off with a timer switch.  But  
still, I think a lot of these systems are unnecessarily expensive.   
Perhaps a lot of it is labor.

-Speireag.