Heating the garage shop

[Howard Caplan]

I'm looking for recommendations and pitfalls to avoid. I haven't informed my lovely yet and she won't be too pleased when she learns her car may be in the drive for more of the year because I am seriously considering heating the garage to work in there all year.
I have a natural gas line about 20 feet from the garage and my first question is, can I run a flex tube/pipe from the outlet to the proposed heater 20 ft away?
Next question is, what kind of heater should I be shopping for? I prefer gas since I have the line so close. I will be heating a garage slightly larger then 2 car and of course, there is no insulation. it is an attached garage which makes me a bit nervous. I saw one heater that has some kind of shield across the element so as not to ignite the chips and dust - is this what I should focus on?

Any advice will be appreciated.

Howard

 

[canoenut]

Gas heater

Not being an expert on gas installations, I believe that your best information would come from your gas provider. Your wife will be very unhappy if the house blows up.

 

[pklonowski]

Canoenut is absolutely correct on all counts. Here are a couple other things to consider:

1) You want the combustion air to come from outside, not in the shop. When you're sanding, all that dust goes up into the air, and from there into the air intake? I don't know if it would ever explode, but it would certainly make a mess of ash inside the combustion chamber, which would require cleaning out too often.

Same argument goes for finishing vapors... I don't know that it would ever get concentrated enough to explode, but your lovely would not be happy if it did.

2) You want the exhaust air to be vented outside, not into the shop. Besides breathing the excess carbon dioxide that's not good for you, the other by-product of combustion is water. You don't want all that much humidity in your shop, as it will warp lumber, rust steel, and who knows what else. It can also condense out of the air after you turn the heat down... rust never sleeps.

3) Insulate your walls & ceiling, & put something on the walls. drywall, pegboard... just something. Tools don't hang well from insulation. Oh, and the heating bill will be less, as well.

FWIW,

 

[garypete]

After-the-fact cheap in-floor radiant heat

Howard,
When I built my 24 x 24 shop on a concrete slab, I put in in-floor heat. It's possible to do that system on an existing concrete floor as I'll describe below.

I laid 2" blue foam under the slab, then wire-tied 400' of inexpensive 3/4" PVC tubing ($40 at Menards) to the 6 x 6 wire mesh reinforcement before pouring the slab. To heat the concrete, I installed a used 40 -gallon water heater set at 120 F, connected the two ends of the PVC tubing to the water heater inlet and outlet pipes, and cut in a small Grunfos water pump into the inlet pipe.

The pump is controlled by a simple line-voltage thermostat on the wall. When the building needs heat and the wall thermostat closes, the pump circulates the hot water through the 400' of tubing; when the building is warm enough and the thermostat opens, the pump shuts off.

The tank always is ready with 40 gallons of hot water (actually 50/50 water/antifreeze to be safe), and there is also a 1-gallon expansion tank and air-bleed valve in the system to compensate for changes in fluid volume as the system heats and cools.

The beauty of in-floor radiant heat for a canoe shop with occasional dust and flammable paint fumes around is that you can isolate the water heater flame from the shop environment in several ways:

1) Build the water heater/pump/expansion tank equipment into a sealed closet in the shop that has an outside air draw for combustion,

2) Turn off the flame and pilot light of the gas water heater anytime you're doing jobs that might create an explosion hazard. With the concrete floor warmed up and storing lots of heat, you can turn off the heater for several hours without a significant drop in the room's temperature.

3) Use an electric hot water heater,

The big question is: Can I do this system years after the floor is poured?

Well, yes, if you have a Gypcrete contractor in your area.

Gypcrete is a self-leveling mixture of gypsum, portland cement, and sand that is mixed to slurry consistency and flooded onto an existing floor to a minimum depth of 1-1/2 inches. When it sets, you have a new concrete-floor, with (in your case) 400' of radiant-floor tubing in it.

 

[john hupfield]

Brilliant.
Me, I burn wood. In my wood shop. Surrounded by Wooden Boats.
Needless to say I am very carefull.More likely to burn the house (just kidding)
Your Fire Insurance would not like that in your garage, though they will tell you the restrictions in a phone call.
John

 

[pklonowski]

I was always somewhat skeptical of the "exploding furnace due to sawdust or finishing vapors" theory, but ten years ago, when I put the heater in my shop, I didn't find anything to refute it. Suffice it to say, I didn't look very hard, as I knew my other half would not believe me anyway. I knew I wanted the exhaust fumes ducted outside, and adding the little bit of ductwork for the exterior combustion air didn't amount to anything, so it wasn't worth pursuing.

All the same, it does reduce the amount of ash that would have collected inside the heater, which, being gas-fired, would be very noticeable (ten years' accumlation has amounted to very nearly nothing). For a wood stove, you wouldn't see the difference.

The heated flooring idea sounds great, as it doesn't mess with head space, and has no cold feet issues. For my next shop...

 

[garypete]

Closet wood-burner

John,
I just use the in-floor heat to maintain a background temp in the shop of about 45 degrees for days when I'm not out there working.

On work days, I fire up a little glass-door woodstove salvaged from a garage sale to quickly bring the working temp rom 45 up to 60 degrees. I find that an air temperature warmer than that puts me into a sweat. I think it's because of the heat radiating up the warm floor.

My insurance company absolutely would not insure a building detached from the house heated with wood. They assume an owner will go out on a frigid morning and fire up the stove to WELD setting, then go back into the house for a couple cups of coffee until the shop is at a bearable temperature. They wouldn't budge, even with my background heat source in play.

So I took out the stove and had the agent inspect the premises. Bingo! Instant approval.

Then one morning when I needed a heat source to steam some cedar ribs, the stove had magically re-appeared. Will wonders never cease?

 

[Dave Osborn]

In my old shop.....

Howard,
In my old shop which was about the size of a one car garage, I used a blue flame heater that I bought at the local Farm/Fleet store. Worked good, cost was low, installation was a breeze, and seemed pretty efficient. No venting, but no apparent CO issues or fumes noticed. I had two 100# propane tanks rented from a local supplier. The only thing that I would have done differently would have been to oversize it based on the BTU rating and square footage.

Now I have a Modine type in my current shop. You may have seen it. It's vented and I had it professionally installed. Dial it down to 45 when I'm not in there, then up to 60 when I'm working.

When painting and varnishing and dust could be an issue, I heat it up to 65 and shut it down. The paint/varnish is skinned over or dry to touch before it cools off to 45 and kicks on again

 

[Steve Lapey]

In my shop I have installed a Modine "Hot-Dawg" ceiling mounted gas fired heater and it works very well.

The unit cost less than $400. and I was able to do the installation myself, but, I did hire a plumber to pull a permit and do the gas piping. Without the permit the propane supplier would not make their connection. Sometimes the gas supplier can do the entire installation without hiring a plumber, depends on the local rules.

Insurance companies have been known to refuse to pay for damages caused by such things as gas heaters installed without the proper permitting so one would be wise to check in advance.

Also, you should check with the local building inspector ahead of time to avoid any unpleasant surprises.

Good luck keeping warm,

Steve Lapey
Stevens Canoe Works
Groveland, MA