Hi all, I've been a long time lurker but first time poster.

We're building a 7200 sq feet warehouse that I want to install radiant heating in. It is just 1 large room. We got an Engineering firm to come and do a heat loss calcuation, and they came up with a value of roughly 300,000 BTU/hr (Outdoor design temp of -33F, indoor design temp of 70F). We then got a heating company to provide us with a quote for materials and labor. The main items they are providing us with are:

- 366,000 BTU/hr output boiler
- 13.2 gallon expansion tank
- 1/12 HP pump
- two 1/25 HP pumps
- 8600 feet of 3/4" piping
- 14 zones between 500 to 700 feet of piping
- a ton of manifilds / thermometers / valves

Now my question to you guys is: Do these numbers sound reasonable? Is it common to split a large room into 14 separate zones? Will the boiler be enough to heat this room?

where are you located and how is the building insulated? 40BTUs/sq ft is a huge load, and -33 is an extremely low design temp.

also I doubt they are doing 14 zones. they are probably doing 14 LOOPs, but unless you have 14 thermostats, you don't have 14 zones.

I am up in Edmonton, Canada. -33 is unfortunately a reality here. And you are correct in that it is 14 loops and not zones. The building is insulated using standard fiberglass R-10 insulation. Is 40BTU/sq ft unreasonably high for radiant heating?

Can you elaborate on the construction? What type of building is it? Given your climate, who advised you to use R-10 and is that the ONLY insulation in the whole building that is being used?

Give a complete description of how the slab was laid out as well, please. (f.x.) compacted dirt/rock, insulator board (if any), reinforcement rod/mesh etc..

Any chance this is a meat storage locker? ;)

 

40 BTUs/sq ft is about a 90 degree floor surface temp; hot enough to start getting uncomfortable.

If your load is really THAT high, fix your envelope first. that's a ridiculous amount of heat loss.

Something's fishy, either your insulation is wildly substandard (as an R10 would be, if that number is accurate), or you have a wild amount of infiltration (perhaps crazy ventilation requirements, or big open doors for long periods of time?).

Thanks for all your help!

Sorry, I should've probably elaborated a bit more. It is going to be used for a car repair garage holding up to 6 vehicles at any one point. There are 6 large bay doors (14' x 16').  Also there are two 40'x5' work pits that are 4' under grade. I have attached a drawing showing the building layout (ignore the part on the right)

I also made a typo, the wall insulation is actually R-12. Roof insulation is R-25, perimeter is R-20. The building height is 22'.  There are no windows. The slab itself will be a 6" slab, with gravel / sand compacted underneath. There will be rebar reinforcement.

Yesterday, the engineering company just came back and recommended an additional heating unit and ventillation system for the repair bay calling for 1 complete air change per hour (160000cfh) for the entire garage. They specified that we get another boiler that puts out an additional 250,000BTU/hr and a few RTU's that can handle 160,000cfh.

Does this sound reasonable or should i be looking elsewhere?

A indoor design temperature of 70° is uncomfortably high for physical labor. The higher the IDT the higher the heat load. My 1989 Fundamentals Handbook (ASHRAE) has eh drybulb Outdoor design temp. at -27°F 99% & -23ºF 97.5% of the time. If I were paying to heat your building the indoor would be 65 and the outdoor -23. The added load is for make up air and I would use a direct-fired makeup air unit for this as they are often shut down after the first fuel bill.