BTU info

[Green Mtn Boy]

Hello everyone, new to the site but have been reading post for a little while. The info is great! I was wondering if anyone can confirm the BTU info I found for concrete using Google. It stated that a pound of concrete takes .2 BTU to raise it 1 degree Fahrenheit. Does anyone agree? Trying to come up with an educated guess on what it takes to raise the temp of my basement floor 10 degrees.

 

[Nofossil]

Another Vermonter! Welcome to the forum.

That number sounds about right - I remember that it's a lot less per pound and per cubic foot than water.

 

[Corey]

0.2 btu /lb deg. F is the number I have seen quoted, and concrete is about 150 pounds per cubic foot. So those numbers should get you started. You're also going to have to estimate the R value between the concrete and the earth (or maybe you've put in a known value of insulation under the slab?) There is also going to be heat loss to the air above the slab, to the walls of the rooms, etc.

 

[Green Mtn Boy]

Thanks for the welcome........I've noticed a fair amount of Vermonters on here. I also see quite a few Tarms. Must be our location, being so close to Lyme and all. I'm running a solo 30 with out storage yet. The house is still under construction but this is the second season I've used the Tarm. I'm fearful that I under sized it though. I'll have three radiant zones when I'm done and a zone for the indirect. The basement is 36 x 48 with embedded pex (this was why I was looking for the info earlier) The two other floors with be 30 x 36 with staple up pex. Those two zones aren't connected yet.....it's a work in progress! I'm not living there yet so I don't feed it regularly but on cold days it has a hard time keeping up. It takes a lot of energy to heat that floor up! I'm hoping that the other zones will help when I bring them on line. The house is super insulated with spray foam in the walls and a combination of foam and cellulose in the ceiling. Any thoughts or prior experiences?