Radiant ceiling and sound isolation

Big Will

Its a band practice room. About 225 sq feet. The load is only 3200 BTUH. A 79 deg surface temp for the drywall gives me 15 btu per square foot. This gives me 3375 BTUH easy money. In the rest of the house I designed for 80-85 deg surface temp for the ceilings. I just don't know how to figure what the 1" air gap and two layers of 5/8" drywall will do to my heat transfer.

Alan(OnVacationInOregon)Forbes

R-values

The R-value of that 1" air space is .8 - 1.0 and I'm guessing the R-value of 5/8" sheetrock is about .5. That would be a total R-value of approx. 2.0. My guess is that it would cut your output in half.

Big Will

At 85 deg surface temp I get 22 per sq foot. With 225 sq. that gives me 4950 BTUH. Half of that is 2475 and that short by a lot. What brought you to that guess. My biggest issue here is I am dealing with a Mech. engineer who stated that it should be fine. He really does not know much about heat calcs or radiant though. So I have to prove my point. Its been frustrating to say the least. This is one of many issues I have had on the job. The funny part is he is there to make sure I do my job right and he has no idea how it really works. He has proved it many times throughout the job.

Alan(OnVacationInOregon)Forbes

I think

most of us have been in your position once or twice with engineers and inspectors who are supposed to oversee our work, but don't know the first thing about what we do.

In John Siegenthaler's book, "Modern Hydronic Heating", Appendix B gives an R-value for drywall at .9 per inch which translates to .5625 for 5/8" sheetrock. So, on the conservative side, .8 + .5625 + .5625 = 1.925 is the R-value for your assembly. Now all you need is an output chart showing BTU's per sq. ft. at different R-values which it sounds, you may have.

I'd write a letter to the engineer showing him your figures and let him make the decision, preferably in writing.

The system might work well on moderate days, but when the weather starts approaching design conditions, on go the sweaters.

EJ hoffman

If you have 1 inch gap

between 2 layers of sheetrock why not run tube in the air gap? Did you include heat gain from equipment/people? Is the band a string quartet or a metal band?

Big Will

its a mid life crisis band

I already ran the tube and plates for this zone. They dont want to pay the extra to change it. The chart is just the one from the CDAM from wirsbo. It does not have numbers for R-value or water temp just the btu output at surface temp with room temp.

EJ hoffman

Men-o-pause band

They won't need heat with equipment and hot flashes, just give them cooling. If they seal up the air gap on the ends you should be more like a suspended tube, you will need hotter water, but again I don't know what ambient temp you are designing for but with heat gain from equipment I would shoot for 60-62 with the radiant. The bodies, lights and equipment will do the rest. Or bite the bullet and retube just the room in the airgap and keep your runs above also.

Big Will

Try as I might I cannot find a table that shows how that added R-value will affect my heat output. Anyone know of such a table?

Mark Eatherton

U R looking in all the wrong places....

Contact Him Li at Uponor and I'm betting he can tell you the answer to your questions.

ME

Mark Eatherton

disregard, double post...

;-)