Need input on 36X56 infloor heat

[Tilt]

I would like a bit of guidance on in floor heat.
The more i look around the forum the more confusing it becomes.
The climate is not real cold in winter (just north of Richmond Va)
The building i am building will be 36X56 X12 with what amounts to a cathedral ceiling(the truss will remain exposed 4/12 pitch and 6 inches of insulation in the roof) the the walls will have 6 in fiberglass.
There will be 2 10x16 insulated garage doors , 1 9X8 insulated garage door.
1 insulated entry door and 5-6 windows.I plan on using 4 inches of EPS foam under the concrete.and 2 inch around the perimeter of the slab.
One company said that i would need aprox 48k btu electric boiler.
I have seen people on the forum use 1/2 pex and some use 7/8 pex
some make their loops 12 inches apart some do it 16 inches apart.
As far as i can tell a basic principal is that all loops need to be about the same length (within 10% i believe)
What i am unclear on is how long those loops should be and i am sure that depends on what size pex i use and how far apart i space them.
Are there any simple rules of thumb to help me do the job correctly?

 

[Dr_Goodwrench66]

I'm no expert, but my understanding is the loops need to be no more than 300' in length max. The spacing may differ in between runs pending your climate. Here in MI, they are 12" apart and 6" on the outside wall.

 

[Tilt]

Thanks Goodwrench but that brings me back to my questions.....
is that 1/2 or 7/8 pex ...
the company i spoke with said i could go with 4 loops of 400 feet with 7/8 pex

so if the 300 foot loop is a good average then that the statement above puts me about 30% longer loop with i am guessing a larger 7/8 pex pipe...

 

[CARS]

When we did mine we did the No More Than 300' rule with 1/2" tubing, 12" on center for everything but the wall that had the doors, then it was closer to 6"-8". I do believe that the door wall was one loop by itself.

Anyway, the guy who does the local installs has done nothing but 5/8" pex the last few years. Regardless, you should at a minimum pay a professional to design your system. Even if you paid him for a couple hours of sketches and load calculations you will know exactly what you need to do and the cost involved. And a plus, even if you do alot of the work yourself, is that if future problems arise with tuning or equipment failure, it's his design and he will be able to fix it. If you install a big box store system, don't expect anyone to help you out in the future.

 

[Tilt]

After doing a bunch more searching and asking i saw a recommendation on this forum for a program called Loop Cad...
After playing around with it for a bit i came up with a design that seems to work
let me know if you see any holes in my plan.
Here are a few of the particulars.

 

[Tilt]

Here is a picture of the layout

 

[rburke65]

I just did a 32'x56'x13 with 1/2" pex, and 1800' pex, 6- 300' runs.

 

[Tilt]

Great, do you have pictures of your installation and finished system on here somewhere rburke?