What’s your heat bill with floor heat?

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Nick Kendall

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I am curious what to expect for heating my 32x56x12 garage
I live in North Dakota and have heard people brag about heating there big shops cheap I am curious how to best heat my garage
Am I better with an oversized boiler that runs for a little bit every hr vs one that runs longer
I want to be able to recover heat loss fairly quick I will also be adding a wood stove to warm up even more when I will be working in there but I want to keep garage 50 constantly
Thanks
 

Taylorjm

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There's nothing less expensive then natural gas of course. With a shop that size, I doubt a boiler is only going to run a little bit every hour, in a ND winter, it's going to be running a lot depending on how much insulation you have and how high the ceilings area. You definitely are going to want a forced air system if you plan on just turning the heat above 50 when you go out there and get some results fairly quickly. I also can't imagine a wood stove doing anything in a ND winter to be of much use in a shop that size. Unless you have it walled off in some areas. I have a much smaller 15x30 shop that's attached to the house and drywalled and insulated. I installed a 90+ efficient 90,000btu furnace and keep it 45 all the time. It's way oversized but I can turn it up to 65 and in 5 minutes, the temp is reached. With a shop that size and your winter temps, you are going to need a lot of heat to keep it that temp.
 

Jadnashua

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Each time a boiler or furnace cycles, you waste some energy and cycles tend to cause more wear on the components than continuous running. From an economy standpoint, one that is just able to maintain that runs nearly constantly will tend to be the most comfortable as well. One that is perfectly sized for the space will not have much if any excess to do a setback, and may never be able to rewarm the place except on a mild day. The suggested sizing is about 1.4x max of the design temperature, so you need to know that.

Want to save some energy, make sure you've sealed all of the heat loss cracks, and have the best insulation that will fit your building.

A school in Minnesota built a gymnasium using ICE (insulated concrete forms - essentially hollow foam blocks filled with concrete and rebar - stacked like Legos then concrete poured to fill it up). They were able to keep the place warm on about $100 worth of heating costs through the winter...insulation makes a big difference along with a tight structure. If I ever end up building a home, I'll probably use them. The huge thermal mass had a big buffering effect to the tune of 3-days or so.

Your first task is to do a good heat load analysis to see what you need to maintain your desired setpoint. Then, you have to decide how fast you want to be able to recover from any setback, which would potentially dictate a larger unit.

IT will also depend on what source of energy you have available, and what their local costs are. Some places, electricity is cheap, where I live, it's not. Same is true with NG and propane.

A hydronic, heated floor tends to be comfortable at a lower air temperature than just warming the air, but is terrible at trying to have any fast response because of the mass involved.
 

Nick Kendall

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Each time a boiler or furnace cycles, you waste some energy and cycles tend to cause more wear on the components than continuous running. From an economy standpoint, one that is just able to maintain that runs nearly constantly will tend to be the most comfortable as well. One that is perfectly sized for the space will not have much if any excess to do a setback, and may never be able to rewarm the place except on a mild day. The suggested sizing is about 1.4x max of the design temperature, so you need to know that.

Want to save some energy, make sure you've sealed all of the heat loss cracks, and have the best insulation that will fit your building.

A school in Minnesota built a gymnasium using ICE (insulated concrete forms - essentially hollow foam blocks filled with concrete and rebar - stacked like Legos then concrete poured to fill it up). They were able to keep the place warm on about $100 worth of heating costs through the winter...insulation makes a big difference along with a tight structure. If I ever end up building a home, I'll probably use them. The huge thermal mass had a big buffering effect to the tune of 3-days or so.

Your first task is to do a good heat load analysis to see what you need to maintain your desired setpoint. Then, you have to decide how fast you want to be able to recover from any setback, which would potentially dictate a larger unit.

IT will also depend on what source of energy you have available, and what their local costs are. Some places, electricity is cheap, where I live, it's not. Same is true with NG and propane.

A hydronic, heated floor tends to be comfortable at a lower air temperature than just warming the air, but is terrible at trying to have any fast response because of the mass involved.
I have plans on adding more ceiling insulation and to continue to make it as tight as possible i am still In the building stage.
What’s a good site for heat loss analysis
I have 2200 ft house and 1800 ft attached garage With 3/4 pex tubes 18” on center
Sealed up good but not great
So roughly 4000 ft structure x
50btu loss=200,000btu I would need
I had a 15 kw boiler for the house but it doesn’t cut it for the garage
I am hoping to be able to heat it for roughly 200$ a month is my goal not sure I am thinking about getting a propane boiler and prebuy my propane in summer to save money
 

Nick Kendall

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There's nothing less expensive then natural gas of course. With a shop that size, I doubt a boiler is only going to run a little bit every hour, in a ND winter, it's going to be running a lot depending on how much insulation you have and how high the ceilings area. You definitely are going to want a forced air system if you plan on just turning the heat above 50 when you go out there and get some results fairly quickly. I also can't imagine a wood stove doing anything in a ND winter to be of much use in a shop that size. Unless you have it walled off in some areas. I have a much smaller 15x30 shop that's attached to the house and drywalled and insulated. I installed a 90+ efficient 90,000btu furnace and keep it 45 all the time. It's way oversized but I can turn it up to 65 and in 5 minutes, the temp is reached. With a shop that size and your winter temps, you are going to need a lot of heat to keep it that temp.
Yes I am seeing the garage is going to take allot more to keep it warm compared to my house
Would it be more cost effective to have a oversized boiler that could heat floor without having to run almost nonstop I see allot of propane boilers up to 200,000btu. I’m assuming stepping to something like that would not have to run hardly at all if my 15kw electric boiler is just a bit small as it has to run non stop
 

Jadnashua

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Each time the boiler comes on, it isn't that efficient at the beginning, and then, some of that heat goes out the flue plus, stuff cools off in between firing cycles. If your 200K boiler runs five minutes an hour, 200K/12=16.67K btu going into the structure. A 16.67K boiler, running 100% of the time will keep it the same temperature, and be more comfortable without peaks and valleys in between cycles. It will also probably use less fuel in the process, especially if it's a condensing boiler, as the return would be cooler, making it more efficient (pulling more energy out of the burner through the condensation). IOW, a huge boiler, running a short time will spend more of its time bringing things up to temp, and be less efficient in the process versus one closer to the actual need that is running steady state.

Many of today's condensing boilers are way more efficient than the older style, over-sized monsters and can adjust to the need.

An in-floor, radiant heating system is horrible at setbacks and recovery. The slab doesn't like super hot inputs, and the thermal mass just doesn't respond quickly to a viable inlet temperature for radiant. A cold-soaked concrete slab could easily take a couple of days to recover. If the shop ever could run without heat for awhile in the winter, you'd have to consider using antifreeze in the water. This will make the heat transfer less efficient by about 10% or so.

Dana is more up on what is a good way to do a heat analysis. Since you don't have an existing system where you could use actual fuel input to calculate, you have to go by the old-style, by using insulation, windows, exposure, and heating zone (design temperature).

The spacing of the pex and the resulting maximum heat transfer will need to be adjusted based on how much heat you need to transfer to keep the temperature of the water at a reasonable level without a lot of striping of the hot/cold areas. Keep in mind that a single loop shouldn't be much longer than 200' or so so that the returning water is not so cold that that area doesn't get much heat. That can be critical if you use a more conventional boiler as those will be destroyed by condensation since they are not designed for it and may need some bypass to keep the return temperature above the condensing range to protect itself, making things more complex. In an area that large, you will need a manifold. You may nor may not need zones, depending on if there's any partitioning or other needs.
 

Nick Kendall

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Each time the boiler comes on, it isn't that efficient at the beginning, and then, some of that heat goes out the flue plus, stuff cools off in between firing cycles. If your 200K boiler runs five minutes an hour, 200K/12=16.67K btu going into the structure. A 16.67K boiler, running 100% of the time will keep it the same temperature, and be more comfortable without peaks and valleys in between cycles. It will also probably use less fuel in the process, especially if it's a condensing boiler, as the return would be cooler, making it more efficient (pulling more energy out of the burner through the condensation). IOW, a huge boiler, running a short time will spend more of its time bringing things up to temp, and be less efficient in the process versus one closer to the actual need that is running steady state.

Many of today's condensing boilers are way more efficient than the older style, over-sized monsters and can adjust to the need.

An in-floor, radiant heating system is horrible at setbacks and recovery. The slab doesn't like super hot inputs, and the thermal mass just doesn't respond quickly to a viable inlet temperature for radiant. A cold-soaked concrete slab could easily take a couple of days to recover. If the shop ever could run without heat for awhile in the winter, you'd have to consider using antifreeze in the water. This will make the heat transfer less efficient by about 10% or so.

Dana is more up on what is a good way to do a heat analysis. Since you don't have an existing system where you could use actual fuel input to calculate, you have to go by the old-style, by using insulation, windows, exposure, and heating zone (design temperature).

The spacing of the pex and the resulting maximum heat transfer will need to be adjusted based on how much heat you need to transfer to keep the temperature of the water at a reasonable level without a lot of striping of the hot/cold areas. Keep in mind that a single loop shouldn't be much longer than 200' or so so that the returning water is not so cold that that area doesn't get much heat. That can be critical if you use a more conventional boiler as those will be destroyed by condensation since they are not designed for it and may need some bypass to keep the return temperature above the condensing range to protect itself, making things more complex. In an area that large, you will need a manifold. You may nor may not need zones, depending on if there's any partitioning or other needs.
Thanks for all the info. So I would ideally want a boiler that would run almost constantly vs one that just runs part time?
 

Taylorjm

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Thanks for all the info. So I would ideally want a boiler that would run almost constantly vs one that just runs part time?

Depends on what you want to maintain the temperature at. You mentioned keeping it at 50 degrees all the time. Do you plan on wanting more heat when you are out there? I keep my shop at 50 and it's miserable to go out there for more than a couple minutes and I'm in Michigan so we have similar climates. It's 7 degrees outside right now. That's why I went with an oversized gas forced air furnace for the quick heat up. Sounds like you have propane available, so that's going to obviously cost more than natural gas. I honestly don't know if a boiler or forced air system would be more efficient in that large of an area. Like others said, insulation will play a major factor. Things like large garage doors are huge areas of heat loss. Personally, I think you are stuck on a boiler system, but I don't think that's going to cut it in a 32x56x12 area like yours unless you are using the boiler and forced air. Just using radiators or in floor heating are going to really have work to keep it warm. If your intent on a boiler, then maybe use that to maintain it at 50 and get a smaller propane forced air system to fire up in an area where you would be working most of the time. With 12' ceilings and I'm sure you have garage doors, the heat loss is going to be tremendous. Just my opinion.
 
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