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.

 

[sdkubota]

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.

1700 SF stacked above one another is a far cry from 4800 sf with 16' ceiling heights. He is heating roughly 6 times what you are given all heat lost from a basement goes to the first floor. Overhead doors are also notoriously bad at air infiltration. Maybe his shop is located above a spent uranium depository.

 

[Renze]

On the end of the road i live on, is a man who put water heating in his shop floor, he runs water from a deep source through it, summer and winter. Its called an earth warmth system. In winter it keeps the shop at 15ｰC and in summer it doesnt exceed 18 because the earth below, gets warmed by the water in summer, which is used in winter.

Not sure of the exact details, but afaik he doesnt heat at all, just buffers it underground.

 

[gkh7890]

Joe G,

I built a 2,550sf ranch w/ walkout basement in 08/09 with a geothermal HVAC system using the ground loop system. Love it! I have a ground loop that has a total of 450ft. of line. Goes out and enters a manifold and then there is a line at 5ft deep, another @ 4ft deep, and a third @ 3ft.

With that said, have you given any thought to putting in a 5ft deep trench and running your own ground loop system (how much land do you have??)? My water comes in the house at around 60F and that is only @ 3ft deep. If you were run a trench @ 5ft in depth and 100ft out and run your line back at 4ft deep and use a low volume pump, I'm sure you could keep the temp around 60F all winter long and use the ground as your heat source.

The same idea could be used for snow/ice control on sidewalks and driveways.

Good luck!

 

[Dr 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!

Hi neighbor
I asked a former employee and he said that was his gas usage for the boiler, there would also be some electric also for the circulation pump. I know there is alot of insulation, foam board with foil and fiberglass, 3" insulated overhead doors. He said the large thermal mass concrete/sand makes it more efficiant.

If you have ever worked in a shop with floor heat, you would want nothing else. This floor does not sweat in the summer, the doors are usualy closed in the summer, its not bad in there even on hot days.

Dave

 

[dclynch]

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.

Redneck I dont know how I could of insulated anymore than I did I used 4 " foam on the floor and on the outside walls. I have R-30 in the ceiling and R-18 in the walls. I have a buddy with the same setup using a natural gas water heater and he says his only const him maybe a 1oo dollars more during the coldest months. Thanks For your input I may just leave well enough alone. I really love getting into a warn vehicle in the morning and being able to work on things without freezing. My only regret is I didnt build it big enough. That is why a new pole barn is in the plans for this coming summer. lol

 

[Redneck in training]

Redneck I don't know how I could of insulated anymore than I did I used 4 " foam on the floor and on the outside walls. I have R-30 in the ceiling and R-18 in the walls. I have a buddy with the same setup using a natural gas water heater and he says his only cost him maybe a 100 dollars more during the coldest months. Thanks For your input I may just leave well enough alone. I really love getting into a warn vehicle in the morning and being able to work on things without freezing. My only regret is I didn't build it big enough. That is why a new pole barn is in the plans for this coming summer. lol

Your building has heat loss. What ever causes that. If you have a friend at fire department they might have a thermal imaging camera. Electricians maintaining transformers and other high voltage equipment might have them too for locating hot spots on switching gear etc. Point it on your house during heating season and you will see where the thermal leaks are.
Funny you mentioned new building. My garage is 27 X 48 and is totally useless for work due to lack of space. I just added new barn/shop 36 X 75.

 

[sdkubota]

Hi neighbor
I asked a former employee and he said that was his gas usage for the boiler, there would also be some electric also for the circulation pump. I know there is alot of insulation, foam board with foil and fiberglass, 3" insulated overhead doors. He said the large thermal mass concrete/sand makes it more efficiant.

If you have ever worked in a shop with floor heat, you would want nothing else. This floor does not sweat in the summer, the doors are usualy closed in the summer, its not bad in there even on hot days.

Dave

I do know buildings with floor heat and they are wonderful providing you heat to a constant temperature 24/7. They are much too slow for occasional heat or lowering and raising building temperature. That said, btus are btus and I hear claims all the time how cheap something is because of this or that. Mainly the people who paid for the system will bend over backwards defending their initial installation costs and over inflate their monthly heating/cooling costs to justify their initial expenses.

 

[Redneck in training]

I do know buildings with floor heat and they are wonderful providing you heat to a constant temperature 24/7. They are much too slow for occasional heat or lowering and raising building temperature. That said, btus are btus and I hear claims all the time how cheap something is because of this or that. Mainly the people who paid for the system will bend over backwards defending their initial installation costs and over inflate their monthly heating/cooling costs to justify their initial expenses.

Floor heating is more efficient in the sense that it makes certain heat sources more deficient. If you pair floor heating with geothermal heat pump you need to pump temperature only from 34 to max. 120 (Typically to about 100). If you pair geothermal heat pump with forced air you have to pump temperature to at least 180F. The smaller is the temperature rise the more efficient the heat pump performs. Floor heating is also marginally more efficient than in example forced air because it doesn't heat air but objects. You can do an experiment. Step on heated floor barefoot and then put socks on. There is definite difference in warmth perception. Standing barefoot it feels cold. Standing in socks it feels warm.

 

[JOE G]

GKH7890 I have about 8 Acres of open land and the rest is woods, Is there a good sight to point me to for info on this system, what are the costs invovled?

 

[jimgerken]

I think there are two reasons radiant floor heat systems are generally more efficient. First, when constructing them you realize that the heat is conducted into the slab for delivery to the occupants and objects, so it only makes sense that you should insulate under the slab. So you insulate. If you were thinking hanging heater you may not think about insulation under the slab (most guys do not insulate under a slab of a shop). There ya go, thats part of the big advantage right there, the radiant building with insulation from the cold ground below is going to be warmer and dryer with the same energy input. The other way RFH systems excell in efficiency is due to the inherent comfort of having the heat below you and conducted up through your feet. Think about two buildings, one RFH, the other forced air. Both are heated to keep the air at 50 degrees. The forced air building will have a cold floor. Standing on cold makes you cold. So you have to turn up the heat compared to the comfort of the RFH building. Turning up the heat means more fuel burned, AND higher air temp which flows thru the ceiling eventually. The higher the temp you keep the air (or any matter really), the more incentive the heat has to flow to colder surroundings to escape (equalize). People say that heat rises. Not true really. Warm air rises because it is less dense. Other than in freely convecting air, heat flows whatever direction it is to get to cold.