attached garage heating ideas

[Jeff H]

HVAC trained tractor guys please weigh in on my idea.

My attached garage is fully insulated, but not heated. If I leave the door to the house open on the weekends it will get comfortable in the garage. But dust, dirt, fumes of course make this not an ideal solution. Not to mention the rabbit that got into the house from the garage with the door open! :laughing:

So to me this proves there is enough heat in the house to share with the garage, just have to share the heat without commingling the air.

On a day like today it's 20 something outside, and 40 something in the garage with no heater.

First idea
So I thought I could run maybe 6" or 8" well sealed metal duct in a loop from the garage. Run it in a large loop through the basement rafters and return it to the garage. If I ran the length of the house and back it would be over 100', and put a fan one end to move the air through. All that surface area of duct could grab some heat from the basement, while keeping the air separate. And in the summer it could give the added benefit of some cool air.

Second idea
A radiator/heat exchanger/coil or whatever you call it in the garage, looped to another one in the basement, fan , and a pump, again to share the heat without commingling the air.

Yes I have examined many of the other options, electric, natural gas,solar, etc. But right now I want to focus on this idea.

So has anyone tried anything like this? I am looking forward to constructive criticism.

 

[SandburRanch]

HVAC trained tractor guys please weigh in on my idea.

My attached garage is fully insulated, but not heated. If I leave the door to the house open on the weekends it will get comfortable in the garage. But dust, dirt, fumes of course make this not an ideal solution. Not to mention the rabbit that got into the house from the garage with the door open! :laughing:

So to me this proves there is enough heat in the house to share with the garage, just have to share the heat without commingling the air.

On a day like today it's 20 something outside, and 40 something in the garage with no heater.

First idea
So I thought I could run maybe 6" or 8" well sealed metal duct in a loop from the garage. Run it in a large loop through the basement rafters and return it to the garage. If I ran the length of the house and back it would be over 100', and put a fan one end to move the air through. All that surface area of duct could grab some heat from the basement, while keeping the air separate. And in the summer it could give the added benefit of some cool air.

Second idea
A radiator/heat exchanger/coil or whatever you call it in the garage, looped to another one in the basement, fan , and a pump, again to share the heat without commingling the air.

Yes I have examined many of the other options, electric, natural gas,solar, etc. But right now I want to focus on this idea.

So has anyone tried anything like this? I am looking forward to constructive criticism.

---------------------------------------------------------------------
Rabbits prefer cooler temps. so 40 something is just fine. In summer turn him outdoors where he can cool with ducting under the slab floor. At 98 F he only needs rump contact but at 104 F full body contact is desirable.:laughing: I had to have a rabbit show me how ignorant I was.

OH, you said constructive. I'm sorry.

 

[CurlyDave]

I am certain you can make either of your ideas work eventually -- for the first one, air-to-air heat exchangers are well understood industrial technology. You will either have to understand this technology on your own, or hire someone who does (not a residential HVAC guy who does not usually deal with this technology).

For the second one, liquid-air heat exchangers are even more well understood than air-to-air ones, but again you will need to either develop your own understanding or get an industrial engineer. HVAC people will usually have little understanding of the process.

I suspect the DIY air-to-air solutions you propose do not have enough surface area to really heat the garage to a comfortable temperature, and there will be a learning curve with more and more surface area added over time to get this to work adequately. (Think $$.) The two air-to-liquid heat exchangers in idea 2 are probably more workable but you have the issue of very low temperature gradients working against you, and really need an engineering analysis to get a system right the first time. You can do it by trial and error, but it will not be an inexpensive process.

I am not certain you have gone through all the downsides of the plan. Every BTU of energy you transfer into the garage is going to come out of the house and your HVAC system in the house is going to have to make up that energy. You don't say how the house is heated, but you are going to use more of whatever fuel you burn due to the added heat load of the garage.

Plus, you are going to be constantly heating the garage. If this is your intent, that is good. If all you really want is heat in the garage a few evenings and weekends for project use, it will use far less energy to put a dedicated, separate heating system in the garage which you can control independent from the house system.

This alternative has two outstanding advantages.

1. The initial cost will be known ahead of time, and there will be no trial and error engineering to produce a working system, and

2. The energy cost will almost certainly be lower due to the independent control of the garage system, even if the energy source has a higher cost per BTU than the main house system.

Your initial post implies that natural gas is available as a fuel source, and the right gas heater will both use an economical, high efficiency fuel source and will have a relatively low initial cost, backed by sound factory engineering.

* * * * *

I am a Chemical Engineer by training, not an HVAC guy, but I know how to do energy balances and operating cost analysis. I hope you take this in the constructive manner I intend.

 

[whistlepig]

I occasionally heat my garage with a kerosene torpedo heater. We have no gas or propane heat here. The house is geothermal. We have a pellet stove in the house for back up heat. I can run the pellet stove with my portable generator. If I would ever go dedicated heat for my garage it would be a pellet stove.

 

[Jeff H]

Hi Dave
The house is natural gas, forced hot air.
Yes I realize that the house would have to make up energy transfered to the garage. I hear you on only heating on the weekends I figured turning off the fan and dampers on each end stopping the air flow would take care of shutting it off.

I was just hoping on a low tech , low maintenance, way to share some heat without having a second heater unit to maintain.


Thank you
Jeff

 

[not2old]

I have 2300 square feet on the main level with a full, partly finished basement. My 600 square foot garage is attached at one end, about 4 steps below the main floor. At temps about freezing, my garage stayed about 38 degrees, too cold to work comfortably, and makes you put on a hat and coat to go find tools. My HVAC system is forced air, geo-thermal. I ran a 6" duct from the upstairs main heat duct through the floor space and terminated it on the garage wall with a plastic adjustable diffuser, left wide open, but easily closeable when heat is not needed. There is no return air from the garage. The thermostat is located on the common wall and now about 52 degrees. I then noticed I had a heat register in the basement ceiling that came from the upstairs zone. I re-directed this to the garage the same way and the temp is now another 2 or three degrees higher. I now find I can work out there in a jacket or my coveralls without getting cold. I'm about to add 220 volt power out there and will add any more necessary heat with a 30 amp, 220 volt construction heater which I've used elswhere and expect that it will raise the temp to toasty in less than 10 minutes. I recently received an electricity bill for the last 2 months for $466.00. The neighbour pays over $500.00 every month for all electric on a smaller house. Works well for me.

 

[whistlepig]

Pellet stoves are sweet if you have ever used one. Not the cheapest heat but for sure a lot cheaper than kerosene. Venting (chimney) is minimal. Just a vent directly out the wall. Pellet stoves are clean burning (no deposits in the flue) and there is virtually no ash to clean out. The heat is as comforting as wood heat with out the hassle of cutting the wood. With only electric here for our geothermal I don't want set up a propane for a garage heater. It would be wood or pellet stove. I did wood as a young pup. Not going back to wood.

 

[adjusterr]

I posted this recommendation previously but will mention it again. I have a 24x40 pole building with 1/2 inch insulboard on walls, roof and ceiling. I found a salvaged Coleman electric furnace taken from a damaged mobile home. The furnace is approx 2'x2'x5', takes air in from the top, past two standard furnace filters and discharges from the bottom. The only modifcation required was a steel stand for the furnace to sit on. The furnace is thermostat controlled and does a great job. This set up is very simple, requiring only a 220v line, no duct work or venting required. I have been using this unit for many years with no problem. Hope this helps.

 

[Sumpter]

If you have gas just run a line to the garage, put a forced air modine type gas heater in and call it good. That is what I had in my shop in Anchorage years ago and it worked superbly.

 

[mjncad]

Jeff:

I understand your desire for low-tech and clever; but I think Curly Dave is giving you good advice.

I don't know how high your garage ceiling is; but if it's high enough, have you looked into natural gas fired radiant heaters? You get the advantage of relatively compact design, sealed combustion with minimal venting requirements, you're not heating the air that will escape from any open gap in your garage it can find, namely around the garage doors. You're keeping your garage and house systems separate. Other than venting, you won't have ductwork to run.

In any case, I think for a residential application, you'll be $$$$ ahead by sticking with a tried and true method to heat the garage.

 

[Redneck in training]

Easy Radiant Works Home

This one option I am considering for my shop.

 

[kidr]

A duct from your existing system to the garage with a manual damper?

 

[bp fick]

I wouldn't mess with the balance of the system presently in the house. You'll only use extra heat occasionally out in the garage anyhow.

I would simply put a supplemental unit in the garage. The choices are endless and many are quite affordable. Simple and cheap ventfree gas heater, repurposed take out gas furnace, hanging unit, radiant gas heater, direct vent gas heater, etc, etc. Sending out a gas line shouldn't be difficult if you can twist black pipe together. Easy.

Natural gas is relatively cheap compared to other energy sources. Since the garage is attached and begins at temps 20 to 40 degrees warmer than the outside air, this is a plus. Most attached garages are.

 

[vwnotrunning]

Keep in mind any air that you direct from your existing system to your garage will be made up with infiltration air to the house from outdoors. A dedicated system will ultimately be less costly. A water to coil type solution will also need freeze protection or remain active all the time to prevent damage in the garage.

If you don't mind trial and error either system you discussed will work.

 

[dqdave1]

I would be worried about odors or worse; fumes; entering your house heating system.

 

[SpudHauler]

I agree with dgdave1, fumes can ruin a nice smelling house and dangerous too.

I prefer Mom's fresh cooked bun smell.

Anyway, my friend has a 14x20 garage that he heats with a propane convection heater using a barbecue tank as the supply. Drilled a hole out through the wall, mounted the small tank on a bracket, put the heater in a corner wrapped in sheet metal on two sides spaced from the wall with copper pipe and had heat and lots of it. Gets great use almost every weekend and the small tank is just fine.

http://www.heatershop.com/mrheater_propane_convection_heater_mh80cv.html

 

[LBrown59]

I plan on using an outdoor forced air gas furnace.

The selling feature for me is the flame is out side instead of inside the building.

 

[mjncad]

Easy Radiant Works Home

This one option I am considering for my shop.

Those are the radiant tube heaters I was suggesting the OP to look into.

 

[westcliffe01]

If you have a building code, it will not allow any of the open flame options, including the pellet stove, any form of wood stove, gas logs etc. The units which will be allowed have to bring in the combustion air from outside, vent back outside and not have the flame exposed in any way. If it is advertised for use in a garage (as compared to a "shop") it should be permitted.

Running a ventless system is dangerous because of the potential for oxygen depletion / CO / CO2 as well as condensation if you are using propane. And, generally, propane is expensive. Not too long ago, I paid $50 to have 2 partially empty 20lb cylinders refilled in Colorado (Grand Junction). In MI, a 20lb exchange cylinder runs $20 at the hardware store. But I digress, it is still expensive.

Having looked online 20lb of propane would have an energy content of 431.6kbtu which at ~$20 translates to 21.58kbtu/$. Diesel fuel has an energy content of 139.2kbtu/gal at a local price of $3.26/gal that yields 42.7kbtu/$, double what you get with propane. If you can burn off road diesel, you might be looking a bit better and if you make a huge propane purchase you might come out a bit better on that one too (I'm sure someone will chip in who solely uses propane).

The only significant advantage with propane is that it may operate with the power out. Otherwise burning diesel fuel is likely to be cheaper. NG is a cheaper than just about anything else out there, but if you don't have it, tough.

 

[dstig1]

I'm surprised you haven't gotten the Safety Police on your case yet, so allow me to step in Code typically requires some sort of a fire-resistive barrier between an attached garage and the adjoining living space. Typically this means something like 5/8" type X drywall (taped and mudded with at least 1 coat) a 20 min rated fire door assembly and to have any penetrations sealed. A duct between these two spaces would send most inspectors into orbit for that reason. Risk of fire spread, CO, flammable fumes, etc make the duct idea very bad.

By far - the cheapest and most efficient route is a dedicated nat gas heater in the garage controlled by a T-stat in the garage. You can get sealed combustion, which is wise, and if it ducts in outside air for combustion and exhausts outdoors too, then you are in the best of all worlds. The ceiling mounted units with a fan are perfect for garages. My neighbor has one and it is awesome.

Electric is workable, but it takes a lot of power to get decent heat and is expensive to run (but cheap to install). Any time you take a step from an energy source to some other form, you lose a lot in the transition. You burn some fuel to make heat to make electricity, and then turn the electricity back into heat in your house, losing energy at every step. Going straight from fuel to heat is by far the most efficient route (within reason). Electric is nice if you cannot get easy access for a gas line, for very rare usage needs, or if you want a temporary solution. I have 2 electric heaters in my garage - 5000W (30A 220v circuit) and 4000W (20A 220v), and they cannot make my (insulated) garage decently warm unless it is mild out - but they can sure make the meter spin! I do not have good gas access in there and they are temporary in my case, so I deal with it.

I wouldn't worry about any extra maintenance coming with a new heater in the garage. There isn't much to them, and they are only intermittently used. Watch Craigslist for used garage/warehouse/dock heaters. Many will be too big, but good sized ones come along. Or just bite the bullet and buy new. You will spend a ton on making your house duct ideas work, so I don't think it would save you anything that way, and the safety compromise is not worth it, IMHO.

Get a gas heater, run a gas line, run a vent/intake, plug it in and go.