Thermal mass is exactly the same as storage for a gasser boiler.....
Not exactly the same, IMO. Here is why: concrete has a specific heat of .2 btu/lb/
![Fahr ::F ::F](/talk/styles/default/xenforo/smileys/f.png)
, water has a specific heat of 1 btu/lb/
![Fahr ::F ::F](/talk/styles/default/xenforo/smileys/f.png)
. A concrete slab in a home is not going be very comfortable with a
![DeltaT ::DT ::DT](/talk/styles/default/xenforo/smileys/deltat.png)
T of more than about 10
![Fahr ::F ::F](/talk/styles/default/xenforo/smileys/f.png)
,and that is pushing it. A thermal storage tank(water) can utilize a
![DeltaT ::DT ::DT](/talk/styles/default/xenforo/smileys/deltat.png)
T of 70
![Fahr ::F ::F](/talk/styles/default/xenforo/smileys/f.png)
+ in a lot of cases . Lets look at a 1000 sq ft slab vs 1000 gals with these approximate usable
![DeltaT ::DT ::DT](/talk/styles/default/xenforo/smileys/deltat.png)
Ts.
Concrete slab:1000 sq ft x 6" thick=18.5 yds x 3900 lbs/yd=72,150 lbs x .2 btu/lb/
![Fahr ::F ::F](/talk/styles/default/xenforo/smileys/f.png)
= 14,430 btu/
![Fahr ::F ::F](/talk/styles/default/xenforo/smileys/f.png)
x 10
![DeltaT ::DT ::DT](/talk/styles/default/xenforo/smileys/deltat.png)
= 144,300 btus stored
Water: 1000 gal x 8.33 lbs/gal =8330 lbs x 1 btu/lb/
![Fahr ::F ::F](/talk/styles/default/xenforo/smileys/f.png)
= 8,330 btu/
![Fahr ::F ::F](/talk/styles/default/xenforo/smileys/f.png)
x 70
![Fahr ::F ::F](/talk/styles/default/xenforo/smileys/f.png)
=583,100 btus stored.
Please, anyone, feel free to check the math-I ain't proud!
That said, I understand concrete can be a necessary structural component, as well as a very good low temp emitter and good thermal mass when passive solar is in the equation. But I maintain that living on concrete, even if it is warm, can be a painful experience for some people. It is just not very forgiving on the body and I believe people need to be aware of this trade off.
it can take upwards of a 1000 gallons of propane to get 250 yards of concrete up to temp the first time....
By the math, as I understand it, it should take no more than about 70 gallons of propane to raise 250 yds of concrete 30
![Fahr ::F ::F](/talk/styles/default/xenforo/smileys/f.png)
. Not sure where the 1000 gallons came from but I suspect this here interweb!
Noah