Radiant floor heat ?

[koditten]

Guys and Gals:

One of the questions I have not seen involves heating a completly cold slab/building.

I was wondering if there is anyone that has a garage with radiant heat tubes in the floor, super insulation, 10' cielings and a gas tankless boiler. The question I am asking involves bringing the garage up to around 55 deg. from a totally cold state. 1) How long if the inside temp is around 40 deg. and outside is 15 deg. does it take for the system to reach equalibrium? 2) Do you take a look at your gas meter and compare start and stop cu/ft radings?

Yes I am aware that these system are designed to be run in a constant state, but there are times, I myself, would not be able to spend time in my garage for 2-3 weeks at a time. I have a hard time spending ANY $ for something I know I will not be using.

I am using the assumption that a 30' x 40' x 10', super insulated garage would not fall much below 35 to 40 degrees with no heat added for 2-3 weeks with outside temps around 15-25 degrees. I am curious if you would be ahead shutting down the radiant sustem.

Thanks

Kirk in Midland, Michigan

 

[v8garage]

Kirk,
I don't know the answer to your question but I know there have been some threads on this subject in the past. You might try our search feature. Welcome to the Garage Journal Board!
V/8

 

[JerseyJim]

I can't give you figures on the cost but I installed radiant heat years ago in a quonset hut about this size. It was well insulated with spray foam. We installed forced air ceiling units as boosters for the system. We were more concerned with quick recovery after doors had been opened. We tried the floor before installing the blowers in the ceiling units. Ended up not installing the fans and disconnected the units, The boosters were not needed. I would expect that depending on the size of the boiler, you should be able to bring this up to 55 over night. The bigger problem that we had was how long it took to cool it down. The key to making it work efficiently is getting a handle on when to turn it on and when to turn it off. There's a lot of thermal mass.

In all honesty, I don't think radiant heat is that good a choice. Hot air is as we all know lousy for homes. But it does have the benefit of bringing temperatures up quickly. I heat my garage this way. I keep the heat at 50 when I am not in it and bump it to 65 when I'm using it. In an area about the same size as yours, it takes about 5 to 10 minutes at the most to come up to temp. Your talking about a bigger differential but it would still be very fast.

Good luck and stay warm.

Jim

 

[jayoldschool]

Mine is about the size you are talking about, but the ceiling is 16'. Insulated R40. I keep the system active all the time, but have it on a manual thermostat that is canted so when it calls for 10 celcius, actual temp in the garage is about 4 celcius. When I am going to work out there for awhile, I just crank up the thermostat. The pump kicks in right away to get the glycol circulating and warms things up pretty quickly.

This is my second winter with the system, and I considered disconnecting it to save a few bucks this year, but it seems to be very efficient so I left it on. My system is designed to run only when the interior boiler calls for heat, in order to be more efficient.

 

[e-tek]

I loked at all the heat-types for my build (24x40x11) and didn't go with in-floor heating for a few reasons - one is what you said, it takes a long time to get any appreciable change in temps. If you keep it just above freezing and then want to go work in there, it'd take all day to get it to working temp...that's why all the above examples ALSO required a blower. As well, if you want to drill a hole (for a lift, a pulley, a post) unless you always know where those lines are you'll be worried about puncturing a pipe - bad news! While we are at it, I also opted not to go for Radiant tube heating. Reasons being the wasted space above, below and to the side (clearance) and how they heat what's right in front of them (metal fenders, your head, etc). The most economical, easy to use and change is an overhead gas blower with electronic start (no pilot light). You can set it for just above freezing, then walk in and turn it up - 2 minutes to comfort. As well, the initial cost outlay is small for a HotDawg, Rennor, etc ($800.00?)
Of course some have in-floor and love it, depends on your needs - like everything!
Hope that helped, good luck with the decision.