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MN Garage Builder
Best Way to Heat a Minnesota Garage

We are building a new 26 by 40 ft garage in Minnesota. So it will be in a cold climate half of the year. It will have an attic truss which will be used for woodworking projects on occassion. The main floor will be used most weekends and some week nights to work on a hobby of vehicle restoration or maintenance.

We have talked with well established contractors in the area about heating sources and everyone is different. Their suggestions range from from a furnace, incandescent to radiant heat. Most shy away from the radiant, which is what we thought we wanted. But none seem to whole heartedly recommend any one thing.

Does anyone have any suggestions or experience (good or bad) with heating a garage in a cold climate that they would like to share?

Re: Best Way to Heat a Minnesota Garage

id say electric heat, you can run a couple 220 lines to the garage for electric baseboard heaters. when you dont need the heat simply shut off the breaker

Re: Best Way to Heat a Minnesota Garage

I would agree that electric would be far less up front cost, however in a really cold climate like Minnesota, natural gas, if available, would be cheaper in the long run, especially if the room is to be kept temperate. A proper size garage type gas heater would also be able to bring the temp up rapidly, even if it is to be kept low most of the time.

There is no time like during construction to pay attention to good insulation. Again, good insulation will bring continued long term pay back. One thing for sure, in the long term, energy costs are only going upward.

Re: Best Way to Heat a Minnesota Garage

I've never lived in 70 degrees below zero, but I tend to go with gas heating, if you have natural gas supply, as Ordjen said.

My main logic: energy costs are going up, and electricity outpaces natural gas.

Re: Best Way to Heat a Minnesota Garage

I'd even consider hot water heat and possibly radiant heat in the slab. If your doing automotive work and have chemicals and gasoline then having an open flame for a furnace would be risky.Besides if you have the radiant heat in the slab that would make things more comfortable having a warm floor while crawling under vehicles.

Re: Best Way to Heat a Minnesota Garage

MN Garage Builder:

You haven't told us anything about what fuels you have available in your location (natural gas, #2 oil) and what type of heat you have in the main house, assuming the garage is being built right next to your main residence.

If it is, you could consider extending, for example a hot water heat/ radiant system into the garage if your boiler has sufficient extra capacity to support the addition.

You haven't indicated how low the temps get during winter in your Minnesota location----you would first have to do a HEAT LOSS CALCULATION to determine how many BTUs/hour you need to heat the new building; from your post, it sounds like you will be using the garage only occasionally, and you could thus save $$$ on something like a forced hot-air system that can heat up the garage quickly when you need it for work, and at the same time present no problem of hot water/radiant pipes freezing when the system is turned off---the problem with HW/radiant is that the tubing has to maintain a certain temp above freezing, so the system has to be emitting heat 24/7, unlike a forced hot-air system or electric heat, that can be turned off when you leave the garage when your work is done without any problems.

I have a garage/workshop just north of Boston, Mass. that's nearly the same size as yours will be; although we don't get the bitter cold of a Minnesota winter, I can tell you that I've never experienced the bitter cold that exists in an unheated garage of that size (approx 1000 sq.ft.); I insulated all the exterior concrete block walls (blown in cellulose) but there's so much concrete in the slab & walls that the cold radiates in & goes right through anyone standing inside this unheated iceberg---my feet & toes feel like a block of ice every time I go in there----I'm just giving you fair warning of how cold it gets in a structure built on a concrete slab with cinder block walls!

Despite this, I couldn't grasp why the previous owner of the property installed an oil-fired FORCED HOT AIR FURNACE rated at 84,000 btu/hr----this seemed WAY over-fired---if you do the math & assign 30,35, or 40 btu/hr (standard heating practice for residential buildings) to each square ft. of garage space, you come up with a forced hot air furnace of 40,000 btu/hr that should easily heat such a garage-----don't you believe it! (1000 sq.ft. garage X 40 = 40k btu/hr assumed needed furnace output).

The PROBLEM comes in when one remembers that the heat in the garage is OFF for 20 hours (and sometimes days) and ON for only a few hours---this allows the radiant cold to seep into the large concrete structures inside a large garage & this bone-chilling cold has to be overcome in less than 1/2 hour in order to make the garage a comfortable workplace without having to wait an hour or two to overcome a freezing garage.

When the previous owner installed the furnace, he didn't bother with any ducting or registers---all the heat comes right out of the large, wide-open plenum & quickly warms the open-space garage within a matter of 15 minutes!

Given that your garage is yet to be built, some people consider embedding 3/4" hi-temp plastic PEX tubing in the poured slab with the idea of installing radiant floor heat when the garage is completed (this would make even more sense if you currently have HW heat with enough added capacity in the nearby house); but again, this would assume that you will want to maintain a heated garage 24/7, and assume the added heating expense of such a decision.

In retrospect, a forced hot air furnace makes a lot of sense for the above reasons, and as well because they are so widespread & widely available---this drives down the price considerably, all you really need aside from the fuel source is a stainless steel chimney thru the roof to vent the combustion gases out of the garage; forced hot air furnaces in the 80k btu/hr range last for decades & a 2nd hand unit would be even less expensive & would do nicely.

Carrier Infinity, Bryant Evolution, Trane, Weil-McLain, Heil, Rheem, York, Thermopride and American Standard all make good units---if you decide on this route, first do your shopping over the internet & look for customer satisfaction/non-satisfaction before you decide to buy.

The GARAGE DOOR is an item that has to be mentioned----buy one that has insulation in its panels---even at that they still let in a lot of cold air because they're large, they're thin, they don't seal well, & often have a lot of glass----a professional installer who can minimize these shortcomings is recommended.

Re: Best Way to Heat a Minnesota Garage

Good answers above but you don't say how much time the shop will be in use. Forced hot air will be the fastest to heat the area but will still take a long time to heat up the slab. If you intend to keep it heated all the time a forced air furnace will suffice however if you will be leaving it unheated for long periods adding radiant heat in the slab in addition to the forced air would be advisable or and insulated floor covering. When in stalling forced hot air you need to not only provide for proper exhaust of the flue gases you should also consider supplying outside air for combustion. This is done for two reasons, one you are not using the air inside for combustion and sucking cold outside air in to replace it, and secondly open flames are a danger in a shop where there is sawdust produced or flammable liquids used.


Re: Best Way to Heat a Minnesota Garage

I would agree with Dobbs, McDaniel & the others on heating suggestions, and would like to hear more from our Canadian friends & those who live on the northern border states of the frozen north.

Since this is a new garage yet to be constructed I think a distinction has to be made between residential garages constructed mainly to house an automobile, and new construction that will be designed to provide a heated environment.

In the first case, the vast majority of existing residential garages were constructed without any thought of a heated residence/workshop/mother-in-law apt., etc; so when such a structure is converted in northern climes to such a use, it becomes a nightmare to adequately heat; the "frost line" in these northern areas can go down to 4 or 5 feet in some places, meaning essentially you have a block of ice each winter under a garage that is trying to double as a heated space.

In the case of a garage yet to be constructed, I would suggest following the techniques used by construction contractors who do slab and monolothic slab construction for homes & multi-use garages where they first lay down 4' x 8' 3" high density styrofoam sheets before the concrete is poured, & also use the same method in perimeter concrete stem walls, as well as often the above grade garage walls.

In the case of heating existing garage structures, the suggestion of McDaniel in covering the slab & even exterior walls with styrofoam, wood flooring & other materials will also be effective for heating purposes.

Re: Best Way to Heat a Minnesota Garage

I remember the old ice cold garage workshop before I moved to Florida. We're re-doing our floors here with a radiant heat system. I sure wish we had floor heating in the old shop. I think it would be cost efficient for a garage workshop like yours, too. I saved this site in my favorites because it's full of handy facts on the subject. You might find it useful for your application. http://www.heattechproducts.com/why-heattech

Re: Best Way to Heat a Minnesota Garage

I have 2 cheap ways to heat your space. Did you consider a wood burning stove. It's probably the cheapest to install and definitely the cheapest to run. You can find free firewood on craigslist all the time. The second is a waste oil furnance. It uses used motor oil as fuel. Also very cheap if not free to run.

Not sure if either of these are practical for you, since both have real drawbacks. But being a cheapskate myself those are 2 option I would give serious consideration.

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