Second guessing

AFOCT

Looked at a radiant slab install for a customer last week. The customer had radiant installed in another building using a different contractor. ( I spent two days redoing that so it was done properly) I had my wholesaler do a heat loss for the new building slab and it just seems off. Might be I have not done a floor in a long time.



40x40 building with a first floor that is 2x6 construction. The slab is basically the basement with the foundation being half above grade and half below. There are two 12x13 roll up doors and a steel entry door. The 8' foundation walls that are below grade are not insulated. 4' slab, 13'6" height to heated first floor ceiling.



Wholesaler came up with 12 loops of 1/2" tubing @ 200' loop lengths.



Designed for 115 water temp at 0 degree design temp.



Maybe I am just off but it seems like a lot of tubing?

Zman

Questions

Are you saying you are heating a 1600 sq foot space with tubing at 9" centers or are there 2 floors?

What kind of underslab insulation?

AFOCT

Answers

The building is basically a one floor house. I am just putting the tubing in the floor of the basement. Unfortunately he purchased enough "insulation to do this floor from the previous contractor. It is insultarp. ( Don't get me started on this stuff) I did talk him into 2" perimeter insulation.

Zman

Output

Siggy's software puts your output at about 62K BTU or 39BTU/ft. at the 115 design temp.

That seems a little high but considering the insutarp (I agree it is crap) and the under insulated walls I think I would run with it unless you do a heat loss calc that tells you different.

Too much radiation is never a bad thing, particularly if you are running a condensing boiler.

SWEI

Not quite clear

Are you planning to heat the basement and let the first floor (which sounds like it could be 4 feet above ground level) live with the leftovers?

AFOCT

.

Yeah the second floor will be heated off a second zone. My heat loss came up with 63k. I think I just haven't done a radiant install in awhile so I must just be overthinking it. The boiler is gonna be condenser.



Thanks for the input fellas!!!

Rich_49

12 @ 200

Is 12" oc layout . 1,600 ft building , 2400 feet of tube .  Besides the lack of quality insulation . Sounds as if the average depth below grade is 4' , any chance the guy will excavate tat and install 2 - 4" of EPS or XPS up against that wall ? That would be a huge help . 

Zman

12"?

Rich,

Wouldn't 12" centers be about 1,600 feet of tubing? It would be a little more for the manifolds but pretty close to a tube every foot. Certainly not 2,400 feet of tube in the floor.

Carl

Rich_49

Z

 there are in fact 3 lineal feet of tubing in two square feet . @ 0" - 12" - 24" .  And due to the time of my post last night I reverted to my default 1 trip to the supply house calculation , I do apologise , after reading this now in my office after coffee and being wide awake I correct myself and say 12" center would require along the lines of  1,850 ft with leader lengths and 9" spacing would require about 2340 feet . You are correct .

Zman

No worries...

I was checking my own sanity more than anything.....

Rich_49

Default in my mind

when I am out in a remote site I always order 3 lineal feet for every 2 square , 0" 12" 24" , 3 lineal feet for 2 sq . We save lots of trips this way and always have stuff in shop for those small jobs .