Installing Radiant in my garage, I have a bunch of ? head is spinning

[GaryGary]

Hi,
One thing you asked is whether radiant is the right way to go. Its a good way to go, but a couple other solar solutions you might think about --
$350 Thermosyphon Solar Air Space Heater (with 1 year payback)
This is what I use on my shop/barn -- its very effective and very cheap -- basically free if you do it on the initial construction of the building and don't put siding under the collector, use polyiso insulation as the back wall of collector, which can also be your wall insulation.
Solar Workshop or Studio
This is what I use in my attached garage/shop -- the thing I really like about it is the really nice daylighting you get along with the solar heating.

This is a pretty nice setup that uses slab floor radiant:
Green Gate Guest House: Solar Projects

edit: should have mentioned that what makes solar work well in a cold climate is lots of collector area, and the air heating collectors are simple and cheap to build large. DIY solar water heating collectors can also be pretty cheap -- about $6 per sqft.

Gary

 

[Rustyiron]

Original OP; When you said "insulating tarp" under the slab, I hope that your are not using that bubble foil stuff. It is a big hoax. Especially under the slab where the foil has no purpose at all. Use a good 2" foam and provide a "thermal break" where your slab contacts the foundation as others have said. Radiant concrete heat is the best in our climate, and your right, you can darn near open and close your doors all day and there is no recovery time like with a hot air sys. But is is not fast responding just by it's nature, this is why a few minutes after bringing in a vehicle, you never notice the heat lost. I use a oil fired, direct vent water heater for backup (normally-wood boiler) and it works nice. I've read that those instant HWH's are really not turning out to be such big savers. When calling for hot water,(running) they gobble up so much (pick your energy source) to raise the water temperature in such a short time (instant) that a normal, modern well insulated HWH really is not much difference to operate because it does not run that often during the day with no use. They made sence to me when they came out, but (now) so does the arguement against them. I also don't have one so take what I've read with a grain of salt. Keep doing your homework, it'll pay off!

 

[Redneck in training]

I also have in floor heat and use a Electric Mini boiler. I would not recommend this option. It works great but is very expensive to operate. I wanted to go with a Hot water tank but let myself get talked out of it. I was working out of town and had to hire a guy to hook it up. He told me it wouldn't cost more that 75 - 100 dollars a month to heat my 24 X 40 pole barn. Well he was way off It costs any where from 200 - 300 more. I just asked for a quote from the Polaris Water company. I will say this 60 degrees is too warm for me. When we had parties I would set it at 60 and by the middle of the evening we were opening windows because it was to hot. Last year I left it at 50 all winter and that seemed perfect it was chilly at first but it would warm up to 63- 67 by the end of the night.

Your cost of heating is proportional to the heat loss of your building. In other words your new heater will have to produce the same amount of heat as the old one. Electric heaters are by principle 100% efficient so if you know how many kWh you used to heat your place you can easily calculate how much propane/natural gas you will burn. Just convert the kWh to BTU, then find how many BTUs can be extracted from unit of the fuel of your choice and divide it by efficiency of your new boiler.
In example you burned $300 at $0.1/kWh=3000 kWh
3000 kWh=10236420 BTU
1 gall of propane is about 91000 BTU
You will burn 10236420/91000=112 gal at 100% efficiency. Since the efficiency of the heater (according to the Polaris website is about 0.9) you will burn about 124 gal. of propane.
Your problem is insulation not the heater.

 

[JOE G]

On a heating website I asked this ? At they are saying that if I used a Propane hanging heater that is 80% and a Propane Water heater that is 80%, I would spend about the same to keep the garage at a constant temp all winter long, even with doors being opened to go in and out and what not, i just figured the Hanging would kick on more often. and this is at 50 Deg set temp..

Do you have Hanging gas heaters you recommend? I am unsure of the rates off the top of my head, propane depends on how much you use for the rate, I use it now for hotwater and coking.

 

[Redneck in training]

On a heating website I asked this ? At they are saying that if I used a Propane hanging heater that is 80% and a Propane Water heater that is 80%, I would spend about the same to keep the garage at a constant temp all winter long, even with doors being opened to go in and out and what not, i just figured the Hanging would kick on more often. and this is at 50 Deg set temp..

Do you have Hanging gas heaters you recommend? I am unsure of the rates off the top of my head, propane depends on how much you use for the rate, I use it now for hot water and coking.

The issue is speed of response. Water heater heating the floor will take about 1 hour/ 2 deg while hanging or radiant tube heater will in general need only few minutes per/deg. Floor heating is very good at keeping the temperature constant. It is also more efficient in the sense that it doesn't heat the air but the objects such as people. It is very efficient coupled with geothermal heat pump because it requires much lower temperature rise than, for example, forced air. It is super efficient if coupled with passive solar collector provided you have the sunshine.

 

[Artisan]

jimgerken,

Do you have any pics of your system by any chance?

 

[sdkubota]

I have a 26' x 40' detached insulated garage. I have two 4800W electric heaters with thermostats and I installed a 7'H x 9'W solar air heater. The solar unit was constructed with some salvaged glass I had and operates on a 70 degree snap switch blower. Once built I realized how little the sun shines although it helps alot with heating costs. I try to keep my garage between 36 and 40 degrees and will turn up the electric heaters when working out there.

 

[Dr Dave]

A local body shop, heates with a small gas boiler, claims to average $100 amonth for the system, during heating season. The temp is set at 70 deg,he can wash a car, and floor is dry in a few min. The building is a 60x80x16, all steel and well insulated. The floor is 6"concrete, on top of 6" sand, on top of 2" foam with radiant tubes stapled to foam. This gives a 12" heated storage mass and eliminates damage to tubing from the concrete pore, and alows for future addition, of hoist and pulling anchor pots. He has 1 hanging furnace for back up heat when doors are opened, it almost never runs. I have worked in this shop many times, doing a/c and electrical work on vehicals, spent alot of times on a creaper, and was very comfortable.

Dave

Dave

 

[sdkubota]

A local body shop, heates with a small gas boiler, claims to average $100 amonth for the system, during heating season. The temp is set at 70 deg,he can wash a car, and floor is dry in a few min. The building is a 60x80x16, all steel and well insulated. The floor is 6"concrete, on top of 6" sand, on top of 2" foam with radiant tubes stapled to foam. This gives a 12" heated storage mass and eliminates damage to tubing from the concrete pore, and alows for future addition, of hoist and pulling anchor pots. He has 1 hanging furnace for back up heat when doors are opened, it almost never runs. I have worked in this shop many times, doing a/c and electrical work on vehicals, spent alot of times on a creaper, and was very comfortable.

Dave

Dave

I would like to see his energy bill... There is no way he is heating a building that size, to that temp, for that amount of money. If I were to make an estimate I would say $500/month.

We are almost neighbors!

 

[megaboz]

I would like to see his energy bill... There is no way he is heating a building that size, to that temp, for that amount of money. If I were to make an estimate I would say $500/month.

We are almost neighbors!

I heat and cool a 3400 sq ft house(basement and main floor) and my electric bill is rarely over $200 a month and everything here is electric. Between the two kids and wife, there is nothing left turned off.

So with a well insulated garage, I could see that as a possibility. Assuming of course he doesn't leave the doors open.