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Heating a detached shop

jyang949's picture

We have an attached garage that is unheated, although it does have electricity. What is the most cost-effective way to heat the space? I have a small plug-in heater, but it probably uses a lot of electricity. 

What about infrared heating? Kerosene heaters? Running a natural gas line? 


SteveSchoene's picture

Running a natural gas line (post #147916, reply #1 of 8)

Running a natural gas line for a direct vent heater would be efficient and have quite a bit lower operating costs that electricity.  It would have greater initial cost however. 

Kerosene heaters and other unvented heaters pump moisture into the air, a real serious rust generator.  Is this attached or detached?  Title and first paragraph conflict,  If attached, and if you use hot water heat, you might run a line to created radiant heated floor. 

What you cannot do with an attached garage is run  hot air ducting into the garage from the house.  Code--and safety considerations--prevent that.  .

Test your finish on scrap, FIRST, or risk having to scrap your finish.

jyang949's picture

You're right, I didn't (post #147916, reply #5 of 8)

You're right, I didn't describe it correctly. 

The garage is stuck onto the back of the house, but there is no passageway from the house into the garage. We have to go outside and use a remote control to open the doors that the cars go through.

I am guessing that the second-floor room was enlarged, and an uninsulated deck attached to the bump-out. These areas are above the garage. So only part of the garage is covered by a heated room.

Technically it is an attached garage, but it's rather primitive and cold.


bill5335's picture

My brother-in-law had a (post #147916, reply #2 of 8)

My brother-in-law had a heater that used natural gas. It was suspended nine feet (or so) above the floor and ran the length of his thrre car garage. I'm sorry I don't know more about it. In my opinion, natural gas would be the most economical.


I have a detached shed and use wood heat, but that may not be a good choice for you.


Stay warm,


bduffin104's picture

Janet, I don't know what (post #147916, reply #3 of 8)


I don't know what your energy costs are in New Jersey but I'd bet it's not cheap. IMHO the most important part of your energy equation would to install a good thick blanket of insulation to the walls and ceiling, then whatever your energy source you will need a lot less of it.

Be careful of ceiling mounted forced air gas furnaces (or electric for that matter) which can easily be compromised by too much dust which has happened to me in a commercial shop I had. Another thing I learned about renting commercial space is if you are in a multi tenant building, rent the space in the middle. That way the tenant's on either side will help heat your space.

I also used to have a shop I heated with a wood stove which was really nice because I could burn all the scraps I would usually have throw away. I considered investing in equipment to make sawdust logs for burning but never did. Obviously in a wood shop you need to be very careful with a wood stove. Under just the right conditions, saw dust can almost explode.

Currently, I'm in a new shop that is still a work in progress. It's about 1000 sq. feet and is well insulated and sheet-rocked with 10" tall ceilings. I used energy efficient full spectrum fluorescent lighting and heat it with a 4500 watt,  220 volt wall hung heater that I can quickly unplug and take outside to blow it out periodically. My shop has a concrete floor which is insulated and thermally isolated from the outside elements which works great as a passive thermal mass and helps with both heating and cooling. I have a box fan mounted in one window which I use to evacuate dusty air from the shop, sometimes even when it's bitter cold outside. The thermal mass of the floor brings the shop quickly back up to temperature once the fan is shut off.

Here where I live, the county owns it's own hydroelectric dam and we literally have the cheapest electricity in the nation. My power bill for my shop this winter is about $25 per month.

JohnWW's picture

Sawdust in the air in a shop (post #147916, reply #7 of 8)

Sawdust in the air in a shop will not explode, the dust concentration needed to create an explosive condition has to be much denser than would ever occur from just working with wood in a one man shop.  Dust explosions typically occur in large industrial dust collection systems where the dust concentration is much denser than ever be created in the open air in a shop.

As already suggested the first thing to do is to insulate the building, given the direction of energy prices, I would suggest going for more than the 6 inches in the walls and 12 inches in the ceilings that is the common standard.  The gold standard for shop heating is a heated floor, everything else is a step, or two, down in terms of comfort and air quality.

John White Shop Manager for FWW Magazine, 1998 to 2007

Davo304's picture

Hi. You got sound advice (post #147916, reply #4 of 8)

Hi. You got sound advice about insulation. Unless you insulate your shop, no sense in heating it. If you can insulate the walls, great, if not, do make sure you thoroughly insulate your ceiling/attic space.

Your type of heating depends on your local utility costs..(.electric  vs natural gas vs oil) as well as the size  ( square footage) of your garage you are planning on heating.  Also, you mention that your garage is ATTACHED to your some cities, building codes prohibit use of natural gas or propane or oil fired furnaces for fear of carbon monoxide being backdrafted into the check your local building codes before making a final decision.

If prohibited, your only choice would be electric heat. If you go this route, buy a fan assisted electric heater. They can be mounted between wall studs for a clean look or mounted on external brackets. Reznor and or King are 2 brands I'm familar with. Your electric supply store could help you much more than I can in choosing the right size/ model.  They can be bought in 110 or 220 volt models. They normally come equipped with built-in thermostats and are very safe and easy to operate.  As for operating costs?.....I haven't a clue.


My DETACHED garage workshop is approx 1,000 S.F.  I installed an 80, 000 BTU Armstrong brand , forced air gas furnace.  This furnace is 90 % efficient, and requires no uses PVC pipe to bring in outside fresh air  to the burning  ( combustion)chamber, and uses another PVC line for exhaust gases. 

A 60.000BTU furnace would have done the job, but my supplier had none in stock so I went with the 80K.  This furnace is positioned in the far corner of my building. I ran a vertical plenum stack  on top, and simply cut in register vents...I ran no trunk lines. This furnace can heat my building in a matter of very efficient and economical.

Because it uses electronic ignition ( Piezo), there is no pilot light to contend with. And because it draws in outside air, the combustion chamber is completely closed off from my shop air ...which eliminates any  possibility of sawdust igniting/explosion.

Because it's 90% efficient, it does require a condensate line. If you have no plumbing (drain lines) for a condensate line to drain into, you could do as I do...which is,  I have my line hooked up to a small condensate pump (approx$30) and run this water into a waiting 30 gal plastic garbage can.  When the can gets full, I pour the water out onto  my lawn in my back yard. This water is just a slightly bit acidic, but no real threat or harm to anything.  Do not run a condensate line out through your garage wall and let the water simply drip onto the ground. The reason not to do this is because eventually the line will freeze up and cause the condensate to "back up" inside your furnace...not good.

My furnace with plenum cost me approx $1,200.  I installed my own gas line from house to garage...this was only about a 30 foot run, and material costs was under $100.


Before I installed this natural gas furnace, I used a propane( barbeque tank) heater set-up for the first 2 years after building my garage.  I would strongly advise AGAINST USING portable propane heaters. It dumps moisture into the building, but more importantly, it dumps carbon monoxide in the building as well. If not properly vented, you will suffer side effects, including headaches, blurry vision...and even possibly death.  After suffering from headaches, even with windows open, I opted for the Armstrong move I ever made.  My furnace is now 12 years old and runs fine. Other than periodic changing of filters, no maintenance/ repairs has ever been performed. None are needed. I highly recommend Armstrong. I  later changed out my house and my Mother's house with the same type of unit; and have installed several others in remodeling jobs I call backs whatsoever.

Good luck on whatever you choose.....and may you stay warm!



Jfrostjr's picture

My preference is for a (post #147916, reply #6 of 8)

My preference is for a radiant heater - if you have sufficient height to get the unit about 8'-9' off the floor, I fired mine with propane until we got natural gas. The switch in fuels was not a problem.

The unit works off a thermostat and has piezo ignition. Therefore, with the thermostat turned down, solvent finishing is safe. Radiant heat warms 'things' rather then the air. These 'things' then radiate heat to the air - and people. As a consequence I have never had a condensation or a rust problem; it is silent and does NOT blow dust around.

Any questions? write.


sidecutter1's picture

Here's what I do. (post #147916, reply #8 of 8)

I moved into  a new house last august.  My new shop is about  12' x 20'   with an other room about 10  x 7.    i insulated the 2 x 4 walls and ceiling  .  vapour barrier and covered with 5/8 t and g   ply,  painted white.  I have a 4800 watt construction htr adjusted to heat to about 68 degrees.  I have a switchby the door.   when I come home after work and if im going to the shop after supper, I turn the switch on.  have supper , then go out to the shop.  it might be a little cool but it warms up pretty quickly.  warm enough to work with out a jacket.     About an hour before I sut down for the day I turn off the htr and the shop stays warm enough to work in till I go in the house.     this works well for me.  I just have to remember to bring in my glue or any thing else that cant freeze. I have a wooden tote that i carry my glue and water stones from the house. no problem.  As an average my htr runs about 3 hours for each session in december  jan and feb.   I go out about 3 times a week  so my htr runs about 9 hrs a week  or 36 hrs a month.  my cost for running this htr  works out like this.

4800 watts running 36 hours a month =  4800 x 36 =172800 for total watts used

172800watts devided by 1000 because we pay by the kilowatt hour = 172.8  kilo watt

Here in owen sound ontario we pay about 12 cents a kilo watt hour. 

172.8  times 12 cents is about $20 .   ( it costs about 60 cents an hour to run one of these)

So i figure if I can limit my shop time in the coldest months  to  three evenings of woodworking a week

it cost me about $20.    I went with a construction htr because there cheap.  about $80.   and there portable.  you can put them away in the summer  I even turn the htr on for a few miniuts on damp days makes every thing feel better.  in the summer I use a dehumidifier.  .    If you have a small shop and limit your woodworking a little in the cold months I can be failrly cheep.   but dont leave it running for days.  or your hydro company will become your best friend. 

let us know what you decide to do.    sidecutter