BTU per square foot chart gypcrete

Radiant23

Hello,

I am looking for a good baseline to go off of to make sure I am heating a renovation well enough. Hardly use gypcrete, but will be using it for a few reasons on the job I am going to do. I am looking for a chart or reference to make sure I am in good shape with my BTU load. It looks like there will be an average of 2” of gypcrete, with a few spots as high as 2 1/4 and a few spots as low as 1 5/8” I am planning on using 3/8” heat pex. I am thinking I will be running water temp around 100 degrees, thinking I will be similar to concrete, but want to verify this. IF anyone can provide some insight or a chart with how much heat I will get at this ratio, or something with some reference to something similar, it would be greatly appreciated. Not asking anyone for a specific answer here, jsut somewhere to get the data to verify. I do a lot of above floor panels, as well as in concrete slab, so just trying to be thorough here. Thanks.

EdTheHeaterMan

Depends your answer is here

Radiant23

HI Ed,

I would ask you to elaborate. I understand multipole variables on this. I know everyone can give the answer of circumstance. The only thing I can say to that answer is I am looking for a reference or chart with gypcrete data and radiant temperature running through it. After looking around for a couple hours here, I figured i would try the forum for some insight, not answers to specifics. I am guessing you do not have something that can help, but thank you for responding.

hot_rod

you will get 2 btus per square foot of floor for every degree difference between the floor surface and the ambient air temperature

For example if the floor surface is 80 degrees , and the room temperature is 68 degrees

80-68=12 x 2=24 btu per a square foot

Doesn’t really matter if it is gyp or concrete, or any other material, it is all about the temperatures.

The key to a successful radiant system is knowing what the heat load of the room is, to assure the floor can meet the heat load

And the water temperature you supply determines the temperature if the floor

The final floor covering acts as a bit of insulation, so that comes into play also

Radiant23

Thank you Hot Rod. I’ll work with the formula and go from there.

Radiant23

Thanks Ed. I’ll look at the info.

EdTheHeaterMan

Wirsbo used to hand out CD's with design software that you could load into your desktop computer. I remember playing with that software years ago, then I stopped because you can just send Wirsbo your design drawings and they would do the calculations for you. They even returned your plans with tubing layouts and manifold locations. That is how they sold the tubing back in the day, I'm not sure if Upinor offers that service anymore.

Radiant23

I remember getting it with a book at a class with my father when I was younger. Unfortunately, I do not have any of that anymore. I do not know if they do that anymore either. I am sure there are plenty of designers out there for this. I also run into jobs where the client has a design, but it is so off the charts that I prefer to do the design myself. I did have a phenomenal resource for this when I needed input, but the man has retired. Since then, it is tough to trust others that offer things that I do not think are right. So I hunt for the info if I do not know. Big believer in numbers do not lie, as long as you do not lie to yourself about the numbers.

hot_rod

https://forum.heatinghelp.com/discussion/comment/1846097#Comment_1846097

this has a lot of useful info. It takes you through all the steps to come up with a design

https://blog.twinsprings.com/wp-content/uploads/2013/05/Uponor-Radiant-Heating-and-Cooling-Design-Assistance-Manual-Part-1.pdf

DCContrarian

https://forum.heatinghelp.com/discussion/comment/1846093#Comment_1846093

But then the question becomes: If I have 2" of gypcrete and water at 100F, what surface temperature should I expect? Or more precisely, what's the highest surface temperature that's attainable?

The answer to that depends on the tube spacing and size, the flow rate, the floor covering. It's affected by insulation below. Instructions for calculating it are on page 70 of the Uponor manual that @EdTheHeaterMan linked to above (page 78 in the PDF version).

The manual actually shows how to calculate your water temperature given your heating load, but you can turn it around and figure out the maximum heating load given a water temperature.

Radiant23

Thanks DC.

psb75

I too noticed that you didn't mention insulation underneath, tube spacing, and what the floor covering material was going to be. Uponor manual has everything you need in it.