Heating a garage or hanger

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Bruce Fenstermacher
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Heating a garage or hanger

Post by Bruce Fenstermacher »

Getting off topic a little. But it is good info and could be related to a hanger. And George brought up heaters.

With the addition of a Bridgeport mill in my garage I'd like to heat the garage. The garage is 22x25x12 (6500sf) with one large garage two, two windows and a man door, all attached to my house. So this would be a small hanger. It It did hold my Cub and is where I recovered the wings so there is a aviation tie in.

I've been heating the garage with a 180,000 BTU Kerosene torpedo type unventilated heater burning sumped Jet A (free). Of course being unventilated there is combustion byproduct in the garage which, no matter how careful I am, reaches my wife's sensitive nose in the house. And of course there is a lot of moisture created by this burning which loves to rust the ways on the Bridgeport and other things I don't want to rust. The garage currently has no insulation. I have to insulate the three walls and ceiling but due to wall thickness can not even bring it to todays insulation standard. I can get R-19 walls and R-30 in the ceiling.

Now living in south eastern PA we see about 2-3 weeks in the 20°s average and maybe 2 months between 28°-38° and maybe days a little warmer. I'd like to be able to heat the garage to 60° and I'd like to do it rather quickly. Going from heat off cold to tolerable and eventually comfortable in an hour lets say. I do not plan to heat 24/7.

So looking online for heater calculations I've found the following simple formula. Insulation quality x SqFt x Temp. differential /1.6= BTU required.
Insulation quality range = use "5" for no insulation, "1.5" for little insulation, "1" for average insulation and "0.5" for very good insulation.
Temp. differential = The temp. you want to heat to minus the coldest outside air temp.
1.6 is a factor for conversion to BTUs.

My formula looks like this:
1 x 6500 x 35 / 1.6= 142,187 BTU
or
1.5 x 6500 x 35 /1.6 = 213,281 BTU.

This seems about right considering I can heat the space with 180,000 BTUs.

I don't have natural gas and I don't have a place or really want to incur the cost of a permanent propane bottle. Electric would be the easiest form of heat to buy and install as I have a 100 amp service to the garage but I fear the electric the most costly to run.

I'm thinking of a propane hot air vented heater that I would hang from the ceiling supplied from 40 lb bottles I'd hook up as necessary like a barbecue. I don't know how practical, safe or legal using portable bottles would be.
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gfeher
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Re: Work in Unheated Uninsulated Hanger

Post by gfeher »

Bruce, check your math. I did all the heat loss calculations when upgrading the heating system in my previous house, an antique wooden frame one, and your results seem high to me. For the size of your garage, even with poor insulation, I would think you should be somewhere below 40,000 BTU/hr. For example, I can't follow how you calculated the SF you used. Short of a radiant reflector system, forced air will give you the quickest temp increase, and of course you'll need to oversize the system a bit to get the temp increase you want in an hour. Also, I doubt I need to tell you this, but check your local codes. Since your garage is attached to your house, you don't want to invalidate your homeowner's insurance by not complying with code. I like your idea of a vented propane forced hot air heater if you can figure out how to deal with the tank in a way that doesn't affect your homeowners.
Gene Feher
Argyle (1C3), NY
'52 170B N2315D s/n 20467 C-145-2
Experimental J3 Cub Copy N7GW O-200
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GAHorn
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Re: Work in Unheated Uninsulated Hanger

Post by GAHorn »

Bruce, in my humbug opinion..... I believe THIS is what would serve you very well:
https://www.northerntool.com/shop/tools ... _200577749
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
hilltop170
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Re: Work in Unheated Uninsulated Hanger

Post by hilltop170 »

Bruce-
Modine and Reznor both make indirect-fired heaters which hang from the ceiling and are built to code. The dealer would be happy to size one for you. They take outside air for combustion and exhaust back outside thru concentric ducting to pre-warm the combustion air. The blower takes ambient air from inside the enclosed space and blows it across the heat exchanger which keeps it uncontaminated.

I have a Reznor in my 42'x42'x18' high hangar in Alaska and it warms up the hangar "right now". There is no reason you could not run permanent pipe to the heater from outside and connect to small propane bottles. That is what I would do if it was my shop under your conditions.

Click/tap on picture to enlarge;
Reznor heater in upper right corner
Reznor heater in upper right corner
Last edited by hilltop170 on Wed Dec 27, 2017 1:10 am, edited 1 time in total.
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
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gfeher
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Re: Work in Unheated Uninsulated Hanger

Post by gfeher »

I now have hangar envy, Richard. :)
Gene Feher
Argyle (1C3), NY
'52 170B N2315D s/n 20467 C-145-2
Experimental J3 Cub Copy N7GW O-200
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Bruce Fenstermacher
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Re: Work in Unheated Uninsulated Hanger

Post by Bruce Fenstermacher »

Gene, your right, I swagged the sqft to 6500. You forced me to remeasure more accurately however and the square footage is 5244.75 sqft. I mainly screwed up my ceiling height is only 9.25' not 12'. Pluging in that new number in to my formula; 1 x 5244.75 x 35 / 1.6 =114729 BTU or 1.5 x 5244.75 x35 / 1.6= 172093 BTU. The 1 or 1.5 represents a very simple heat loss method. I could find a calculator that takes into effect the type of construction, size of the windows and doors and their construction and maybe more accurate.

George, why would you think a 50,000 BTU heater would work? Of where you just pointing to the type of heater? I've seen these heaters and the trouble is figuring how much heat I actually need. I could get two of these at 80,000 BTU for a total of 160000 BTUs but I've doubled the cost and fueling trouble.

Richard, what size heater do you have in your hanger. What is the average outside temp and what could your heater heat the hanger to? And like Gene I have hanger envy but as my 170 lives outside, sometimes a heavy tarp brings envy. :D
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hilltop170
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Re: Work in Unheated Uninsulated Hanger

Post by hilltop170 »

My plane sat outside from 1951 until 2006 (55 years) and sat outside in Alaska from 1984 to 2006 so I know how it feels. I did some horse trading and creative financing over about 10 years to finally get that hangar and believe me I feel very fortunate to have it.

I don't know what output the Reznor has but I will be back in Alaska Jan 3 so I will look it up. The hangar has closed cell spray foam insulation so it is just about like a thermos bottle. The winter temps average around 10°F with about 3 weeks below zero. I leave the temp set at 40°F with the thermostat about 4' above the floor and the upstairs "office and break room" stays at about 60°F. To heat down to the floor to 65°F takes about 10 minutes and upstairs is about 75F. Ceiling fans would help the circulation but they are not there yet. The monthly gas bill runs about $40 but there are hangars on both sides so that helps, I only have to heat the front, back, and roof 100%.
Last edited by hilltop170 on Wed Dec 27, 2017 1:14 am, edited 2 times in total.
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
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gfeher
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Re: Work in Unheated Uninsulated Hanger

Post by gfeher »

Bruce, your result still seem very high to me. Ballpark heating requirement typically use 35-45 BTU/hr/sq. ft, based on the floor plan square footage and using the higher number (45) for colder climates. HVAC contractors usually now use Manual J calculations/software. Google "manual J calculations" and you should be able to find an on-line HVAC calculator based on the manual J calculations. They are kind of complicated and designed for whole house calculations, but you can still use them for a single room like a garage. I think that you will see that your requirements are a lot less, and closer to what the heater George recommended puts out.
Gene Feher
Argyle (1C3), NY
'52 170B N2315D s/n 20467 C-145-2
Experimental J3 Cub Copy N7GW O-200
bagarre
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Re: Work in Unheated Uninsulated Hanger

Post by bagarre »

My garage is 20x25 with 10 foot ceilings on one side and the other is vaulted to 20 feet. Odd ball ceiling because there is a living space above half the garage. 1 full exterior wall with a window and the wall with two garage doors. The doors and walls are insulated and I spent some time getting rid of all the drafts.

I heat the space to 60 degrees all winter (Northern Virginia) with a 220 volt 5000 watt space heater. It works very well.
I can leave it unheated and bring it up to 50 or 60 degrees in 15 minutes but tools, floor and everything else are still cold so the heater keeps running. Keeping it semi heated 24x7 keeps surfaces comfortable and the slab can retain heat as well. The heater seems to run less.

The whole house runs on electric heat so my electric bill is fairly constant year round. I cant say how much of the bill goes to the space heater.

Using a 220volt plug avoided several building code conversations and lets me run a beefy window AC unit in the summer time.

5000 watts is over kill for this space.
heater.jpg
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gfeher
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Re: Work in Unheated Uninsulated Hanger

Post by gfeher »

5000W = a liitle more than 17,050 BTU/hr, assuming 100% efficiency of the electric heater. (1W = 3.412 BTU/hr) Electric heaters are generally considered to be 100% efficient for this conversion.

To give you another idea of the heating requirements you are talking about, Bruce, my two-floor cabin in upstate NY with a footprint of about 25' x 20', lots of windows, 8 1/2' ceiling on the first floor, is heated by a single propane fireplace insert that puts out a maximum of 27,500 BTU/hr, and the cabin is toasty in the coldest of weather, no problem.
Gene Feher
Argyle (1C3), NY
'52 170B N2315D s/n 20467 C-145-2
Experimental J3 Cub Copy N7GW O-200
hilltop170
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Re: Work in Unheated Uninsulated Hanger

Post by hilltop170 »

No matter what you use as a heat source, effective door/window seals and good insulation are the keys. Spray foam, in my opinion, is the absolute best there is. Applied properly, it seals all air leaks and actually strengthens the structure. Open cell is cheaper and can be used where there is no possibility of moisture intrusion. Closed cell seals out moisture, is an effective moisture barrier, and any that gets in will not penetrate or be retained in the foam. Foam is also more easy to apply in most cases than anything else. Strip out the sheet rock and spray against the outer wall sheeting and you have a thermos bottle. Fiberglass in the ceiling might be more easy and more cost effective but spray foam done properly insures no air leaks. Of course, then you have to insure you have adequate ventilation/air changes.

Double ot triple pane windows and max-R-rated garage door all figure into the equation as well.

Pay-out is different with each application and may take years, but if you intend to stay in the house long-term, spray foam with the other upgrades is the way to go. Then you're all set up for air conditioning in the summer as well!
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
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Bruce Fenstermacher
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Re: Work in Unheated Uninsulated Hanger

Post by Bruce Fenstermacher »

Gene, I will look up manual J calculations. I'd love to find I could use a much smaller heater.

Richard, I'm 61. I know I'm in good company here. I might even be a youngster to a few. I don't plan to ever move but then there is reality. As time moves on we don't plan a lot of things we have to do. Point is investments made in the house have to make sense for resale which is when payback may occur.

I always thought foam looked cool being installed. But I understand it's not really suited for do-it-yourself. Probably fiberglass batting in the walls. Maybe I'll sheet rock over it. Blown in insulation in the ceiling. Garage door is already foam insulated and the windows in the garage are the same as those in the rest of the house.

This is a bit frivolous, heating the garage for 30 days a year. But if i don't I'll never get my money out of that Bridgeport I just installed. :roll:
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gfeher
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Re: Work in Unheated Uninsulated Hanger

Post by gfeher »

Bruce Fenstermacher wrote:This is a bit frivolous, heating the garage for 30 days a year. But if i don't I'll never get my money out of that Bridgeport I just installed. :roll:
Not frivolous at all. A Bridgeport? Again, I'm envious. :)
Gene Feher
Argyle (1C3), NY
'52 170B N2315D s/n 20467 C-145-2
Experimental J3 Cub Copy N7GW O-200
hilltop170
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Re: Work in Unheated Uninsulated Hanger

Post by hilltop170 »

No kidding! I have always lusted after a mill! Or even a lathe.

That garage would be my new home if I had one. At 61 you have another 30 good years of machining ahead of you, go for it! I put up 5/8" OSB from Home Depot around my hangar instead of sheet rock. It is much tougher and you can use screws to hang stuff off the walls.

And remember that insulation works the other way just as well when you talk Teresa into an air conditioner next summer. That Bridgeport needs stable temperatures and dry air to maintain its precision. :D
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
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Bruce Fenstermacher
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Re: Work in Unheated Uninsulated Hanger

Post by Bruce Fenstermacher »

Thanks guys. Richard, my lathe is in my basement. I couldn't (easily) get the 2000lb Bridgeport down there. Your hanger looks like a perfect shop to slide in a lathe, mill, jump shear (larger than my 30" inch shear) roller, stretchers and shrinkers, english wheel and on and on.
CAUTION - My forum posts may be worth what you paid for them!

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Email: brucefenster at gmail.com
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