We just built our Garage and have the heating system finally up and running. The building is 26x36 with the shop area being 26x26. The back 10 feet will have a hot tub and shower/washroom area. Garage height is 10 ft plus a couple of inches. We have radiant heat in the floor powered by a gas boiler.

It gets damn cold up here especially right now. What is the most efficent temp to keep the Garage at (economically)?

We keep our shop about 60-65*. That way it is comfortable with a set of cover-alls over your regular work clothes (jeans/long sleaves). If you get it over 70* you start sweating like a hog.

Hey do you have any pics of your new Shop? A friend is going to be seting one up this summer..

That sounds like you have a very nice set up. I would love to have a place like that to work on my Jeep.
Going with Radiant floor heating was very wise of you. It is a great source of heat, it is a nice consistant heat, and it will save you a lot of $ in the long run because it is a nice energy saver. Plus if you are going to have a hot tub.... Nothing beats a nice warm floor on your feet.
One downfall of radiant... (and I don't even think it is a down fall at all, I think radiant heat is the best system out there) is that it is a little slow in reaction. Where if you have a fan coil in a garage you can leave it at 40 until you get in there.
I would probably leave it at 50 or 55 and if you know you are going to use it turn it up to 60-65 about an hour to 45 min before you start work. If that is not possible then just leave it at 60 all the time, like I said radiant is very efficent.

One thing to keep in mind with that type of heating system is make sure your thermostat is not in a hot spot. Like near your hot tub or near a heat producing tool. If the Tstat shuts off, because it is in a hot spot and your slab goes cold, you will lose all your effective heat.
Like I said great choice of heating systems. I wish I had a set up like that.

pics please

Could you mix in some solvent and degreasers and whatnot into the hottub after a long day of getting dirty on your jeep? Kinda like a parts washer/ hot tub thing. [img]images/graemlins/tongue.gif[/img]You could keep your sink clean... I'm just being stupid. But I'd like to be your neighbor... ooooh... pics please

No pics yet, I'll wait until the interior is done up nice and purty before posting...probably in a few months..gonna take our time as this was our first construction project. The girlfriend and I did it almost all by ourselves and I was her assistant/helper. Gotta love a girl who can build a garage for you . loves the sound of a diesal and thge smell of gear oil.

But getting back to the cost of heating...what I am wondering is it more economical to keep it at a lower temp and then increase it when you need to or find a constant temp and just leave it at that. The slab once warmed up should retain it's temp and not cost all that much to maintain. Any thoughts.

The most important thing to remember when heating anything, is delta T. That is: Temperature inside - Temperature outside. The higher you keep the temperature inside, the bigger your heating bills will be. If the garage is well insulated, (especially the slab, since you have a radiant slab,) keep it at 55-60 degrees.

On your comment, once the slab is warm, it will still take heat input to keep it warm. Consider your slab as just a big low temperature radiator. it is designed to give up heat to the heated space. As fast as the heated space gives up heat, the slab has to provide it. Because there is so much mass there, it does take some time for any change in thermostat set point to affect the room comfort. On that same thought, if you have the temp. set point at 50 degrees, and you go in and turn the temp up, the heat required from the boiler will be way in excess of the heat required from a radiator or fan coil unit. But, after the heat is in the slab, if you turn down th t-stat, the room will stay warm for a long period of time while the slab cools down. That is the down side to radiant slab heat. Not real good for varying indoor temps in the short term. Also, if you have your heat turned down, come in and crank up the t-stat, because the slab takes so much heat, and responds so slowly, the slab will tend to overheat, and shoot past the set point on the t-stat, further adding to your heating costs. This can sometimes be mitigated with a "smart" t-stat that learns the heat loss characteristics, and compares inside and outside temps to prevent overshooting set points. In reality, Slab heat should be used in a steady state mode, with very little temp. variance.

Just a suggestion on your construciton. If, you don't have the slab insulated very well, I would suggest doing it pronto. If not, your efficient heat will be used to thaw the ground around you more than heat your building. As a minimum, I would suggest an R-10 foam board extending vertically from the slab to 2 feet below the footing or 4 feet deep, whichever is more. Excavate along side your building 4+ feet and install this tight against your foundation. With slab heat with out insulation under the slab, you effectively are heating the entire block of earth under the slab. The perimeter of the slab loses the majority of the heat. Your goal with this insulation is to stop this loss.

jfralph

Thanks for the info. We have insulated the slab but not to the degree that you mentioned. We were following guidelines in literature that we had on radiant heating. We have the slab insulated down about 18 inches and then out about 18 inches. We used the blue hard foam insulation about 2 inches thick...not sure of the R rating off the top of my head. We did not insulate under the slab as it would have been quite expensive using the hard foam insulation.....we found out later that we could have used bubble wrap which would have been cheaper...can't do anything about that now.

Our walls are insulated with R20 and ceiling with R40 fibreglass insulation.

I realize that with radiant heat it takes a long time for temperature change that is why I want to keep it at a constant temp as oppose to turning it up a couple of hours before going into the shop.

See the problem is that my girlfriend is frugile...well actually she is darn right cheap...she is the original Jewish Scottish Princess [img]images/graemlins/smile.gif[/img]. She wants to keep the temp at around 40 and I want to keep it at around 55. For just having the vehicles parked in the Garage the 40 is fine but I'm not wrenching or hanging out in the Garage at that temp, so the temp needs to be adjusted for that.

I'm gonna jump on the jelousy band wagon. Tracking down the fouled sensor in my YJ last weekend was headache enough. When you factor in the 34 degree temp, slight breeze it got worse. After about 2 hours the rain started...icy wet nasty type of rain. I'd have paid blood for an unheated garage.

Anyway...When I was a kid our garage was heated by an oil heater. The kind that hangs from the rafters and just screams death trap. About 3 years ago my parents sold the house and an old high school buddy told me the garage went up in flames the next winter. Good call on the radiant heat. I had radiant heat living in Korea and kept the temp at 50. The house had horrible insulation but 50 kept it decent while I was gone and I'd just turn it to about 70 when I got in and it kept the bill cheap.