Geothermal in floor heat question.

[backintheday]

Happy Friday
I'm building a 40 x 60 pole barn in the next couple years and have been leaning towards geothermal for heating and cooling. I'll be doing most of it my self so I'll be digging a trench for the pipe run. My question is is just circulating the 55 deg water through the slab be enough to heat the slab or does the slab have to be heated to a much hotter temp to make the shop comfortable. I plan on an inch of closed cell foam with either batts or blown in on top of the foam.

Thanks all

 

[anthony666]

if 55 is comfortable for you then you're ok just putting that temp into the floor .. if you want it to get it warmer in the garage you're gonna have to turn on the heat pump

 

[ratdoggy]

Where are you? It would affect your payback on the system.
I was thinking of adding Geothermal to my new house but the payback was something like 20 years and by then the equipment would have needed replacing so to me it wasn't worth it.

 

[Highbeam]

You must be in a warm area to assume that the ground temp is 55 at trench depth. Even warmer to assume that you won't be cooling that trench dirt with your loop. See, as you steal heat from the slab you are stealing heat from the trench and will cool your trench dirt in the area of the trench.

Are you even planning on installing the compressors?

 

[theoldwizard1]

if 55 is comfortable for you then you're ok just putting that temp into the floor .. if you want it to get it warmer in the garage you're gonna have to turn on the heat pump

It depends a lot on what kind of work you are doing.

Light work or lots of standing/sitting on a 55° floor and your feet will be cold regardless of any other heat sources. If you are going to be laying on the floor under any vehicles, you will be uncomfortable.

Radiant floor heat does not handle wide swing in temperature quickly, so you really don't want to lower it more than a few degrees over night. The best solution (also most expensive), especially if you are going to be opening and closing a large door frequently, is a second heat source, such as a high wall unit, which could be connected to the same outside unit.

They do make split systems that have multiple heating/cooling zones and a radiant floor heat exchanger is an option.


Geothermal, although expensive, is a great way to go. You need a plan for long term power outage. A propane powered generator large enough to run the heat pump, a propane fireplace, or the capability of letting the building and plumbing "freeze".

 

[theoldwizard1]

I plan on an inch of closed cell foam with either batts or blown in on top of the foam.

"You pay for insulation once, you pay for heating/cooling fuel every day !"

IMHO, you want at least 4" of foam in the floor and don't forget the edges.

Look into the newer high efficiency split heat pumps, especially ones that have multiple zones. Almost as efficient as a geothermal but you do not need a well.

 

[jkeyser14]

Where are you? It would affect your payback on the system.
I was thinking of adding Geothermal to my new house but the payback was something like 20 years and by then the equipment would have needed replacing so to me it wasn't worth it.

The loop is a significant portion of the cost, my loops have a 55 year warranty and will much likely last much longer. In 20 years you will only need to replace the air handler, which is just barely more expensive than a traditional air handler. It also does both heating and cooling, so you don't have to worry about the hassle and service fee costs of replacing both outdoor and indoor units when they fail.

As for payback, it depends on each individual situation. Mine is less than 7 years.

You need a plan for long term power outage. A propane powered generator large enough to run the heat pump, a propane fireplace, or the capability of letting the building and plumbing "freeze".

You make this sound like only a geothermal problem, but most people have no such provisions for their current HVAC systems. A natural gas fired furnace, wood burning furnace, or oil furnace will not run during a power outage.

 

[backintheday]

I live in NW Wyoming, 75 miles south of Jackson, It's pretty cold up here, a few years ago we had -30 temps for at least a month. But we get a foot or so of snow that seems to insulate the ground somewhat.
The floor insulation will be 2" rigid, the walls will be 1" foam and R13 batts or maybe blown in cellulose, not sure yet.
The compressor is what I'm wondering if I need, I was thinking that the 55 deg temp would be comfortable but I didn't taken in to regard standing on a cold floor, that's a good point.
I own my own backhoe so the excavation cost will be my labor and fuel cost. If need be I can get a track hoe to dig deeper.
I live in an area with lots of beetle kill so I was planning on a wood stove for secondary heat.

Thanks for all the info guys.

 

[backintheday]

Also, I don't have access to natural gas, it's either electric, wood or propane, we all know how expensive propane is, it will take alot of wood and maintenance to run a wood boiler and electric is going to keep getting more expensive. That's why i'm leaning towards geothermal.

 

[anthony666]

do your homework about how many slinkys you should put out and then put in a couple more .. that way if you lose one to an act of god you still have back up slinkys to carry the load and make sure you have an easy way to shut them off, you dont need to beat the **** of your backhoe in the middle of january trying to dig up a manifold to kill a bad line .. as soon as your lines come up above the frost line insulate the hell out of them and seal them up tight with vapor barrier .. ground water will wick any heat out of your line sets faster than you can drag it out of the ground .. plumb a bypass to whatever heat pump set up you install so you don't put any fluid through it when it's not running .. if it was me, i'd run the fluid from the slinkys through a heat exchanger and then out to the floor to isolate the two circuits .. and make sure you put enough glycol in all parts of the system for worst case scenario freeze protection

thats all i can think of right now .. hope it helps and i hope your passive geo system pans out, please let me know

 

[anthony666]

oh yea .. being rural, you probably have a septic tank .. they make a ton of heat .. throw a couple of slinkys in with your poo, every little bit helps

 

[backintheday]

Good idea about the poo tank!!
Thanks for the tips. I doubt ill be able to afford a floor this year so ill have plenty of time to research. Keep the ideas coming.

Thanks much

 

[backintheday]

For those of you that have this set up what tempratures do you have your buildings set at and what is the temp of the liquid entering the floor to achieve that temprature?

 

[encantofred]

i have geothermal in my cabin in the mountains and it has worked great for years. it is from earthlinked.com

it is a direct exchange system where we drilled holes vertically in the ground 100 feet deep and put the freon lines in the holes.

i have a 3 ton unit and it is a cube 2 foot square.

it gets down to zero degrees where i am at. these same units are used for infloor heating and even driveway heating.

tom

 

[theoldwizard1]

Also, I don't have access to natural gas, it's either electric, wood or propane, we all know how expensive propane is, it will take alot of wood and maintenance to run a wood boiler and electric is going to keep getting more expensive. That's why i'm leaning towards geothermal.

Those are some of the BEST reasons for geothermal !

 

[theoldwizard1]

I live in NW Wyoming, 75 miles south of Jackson, It's pretty cold up here, a few years ago we had -30 temps for at least a month. But we get a foot or so of snow that seems to insulate the ground somewhat.
The floor insulation will be 2" rigid, ...

What is code for foundations ? 48" ? That means that the ground can freeze that deep.

I can not say t enough ! "You pay for insulation once, you pay for energy every day for the rest of your life !"

If it was me, I would put at least 4" of rigid foam under the floor, and dig a 48" deep trench around the interior edge and install 6" of foam. The ground will only be near 55° F near the center of the floor. Near the edge it will be much closer to the ambient temperature. So 4' from an exterior wall the soil underneath the insulation could be below zero !

the walls will be 1" foam and R13 batts or maybe blown in cellulose, not sure yet.

No where near enough !

... I was thinking that the 55 deg temp would be comfortable but I didn't taken in to regard standing on a cold floor, that's a good point.

Over 50 years ago, my uncle installed radiant heat in his basement floor because his wife complained about the cold floor while she was running her basement drapery/upholstery business. As a kid, I remember walking around in stocking feet on that warm basement floor in the middle of winter. It was wonderful !

I live in an area with lots of beetle kill so I was planning on a wood stove for secondary heat.

Maybe the wood stove should heat the floor and geothermal heat pump just provide forced air heating and cooling. For a 40x60 you are going to need 3 or maybe even 4 interior units.

 

[backintheday]

As far as the under slab and around the slab insulation, I just built my own house using ICFs so i understand where you coming from. I plan on going 4' out from the perimeter (so the insulation would be 48 x 68) and then going down 4' from there, unless ya'll can think of a good reason not to.

I don't want any kind of forced air in the shop, the more i read about the geothermal heat pumps the more I like them.

Ironically I have spent most of the day repairing my septic tank, there is a leak at the inlet so when all the snow melted it leaked into the tank and over worked the leach field, there is a lot more to the story but I thought it was ironic the day after someone mentioned dropping a line in the poo tank it plugs up.....

Thanks again for all the tips, keep them coming.

 

[anthony666]

last time the guy came out to empty mine he dumped about a gallon of chocolate soup out onto my deck reeling in the hose .. i said 'don't worry i'll go get the hose and wash it off' .. he bent down and scooped it up with his bare hand and nonchalantly flicked it back into the tank .. i'm gagging just writing this

sorry for jinxing you

 

[backintheday]

No worries, i installed the septic system so something was bound to happen

Once you've burned poo in iraq, nothing much bothers you, but i didnt pick up any with by bare hands.

 

[stingry]

Happy Friday
I'm building a 40 x 60 pole barn in the next couple years and have been leaning towards geothermal for heating and cooling. I'll be doing most of it my self so I'll be digging a trench for the pipe run. My question is is just circulating the 55 deg water through the slab be enough to heat the slab or does the slab have to be heated to a much hotter temp to make the shop comfortable. I plan on an inch of closed cell foam with either batts or blown in on top of the foam.

Thanks all

I do not think that you would be pleased with a 55 degree floor temp. Here is why and this is based on real experience NOT on theory or supposition. My shop is 3600 sq ft, R40 ceiling, R25 walls and 2"XPS under and around the 5"
slab. So I am well insulated. I have pex in the floor for radiant heating but did not install the heat source so I have no heat this winter. This is what I have observed: The ground under the slab is a constant 47 degrees. I have a temp probe under the slab 4' from the slab edge. Therefore the slab temp is also 47 degrees. I live in Western Nebraska where typical daytime temps are in the 20's and 30's and nighttime lows are single digits and the teens. When the temperatures were relatively mild, the AIR TEMP in the shop was 47 degrees or a little warmer, BUT when the temps dipped into the singles digits or below zero (Fahrenheit) the AIR TEMP in the shop dropped to as low as 35 degrees. This was because the slab could not radiate enough heat to overcome the heat loss thru the walls, windows, doors and ceiling. I believe you would see the same types of AIR TEMP swings with only a 55 degree slab temp with no way to increase the slab temp.



Cheers
Steve

 

[78Bird]

How about passive solar? set up a panel of piping to catch max sun, maybe even a standalone pump on a smaller PV panel, so it collects and pumps heated coolant in the daytime but shuts off after dark so as not to radiate it back out.

would be a cool DIY project. Could even incorporate some reflectors to concentrate the sun for higher temps on the collecting surface.

 

[backintheday]

I do not think that you would be pleased with a 55 degree floor temp. Here is why and this is based on real experience NOT on theory or supposition. My shop is 3600 sq ft, R40 ceiling, R25 walls and 2"XPS under and around the 5"
slab. So I am well insulated. I have pex in the floor for radiant heating but did not install the heat source so I have no heat this winter. This is what I have observed: The ground under the slab is a constant 47 degrees. I have a temp probe under the slab 4' from the slab edge. Therefore the slab temp is also 47 degrees. I live in Western Nebraska where typical daytime temps are in the 20's and 30's and nighttime lows are single digits and the teens. When the temperatures were relatively mild, the AIR TEMP in the shop was 47 degrees or a little warmer, BUT when the temps dipped into the singles digits or below zero (Fahrenheit) the AIR TEMP in the shop dropped to as low as 35 degrees. This was because the slab could not radiate enough heat to overcome the heat loss thru the walls, windows, doors and ceiling. I believe you would see the same types of AIR TEMP swings with only a 55 degree slab temp with no way to increase the slab temp.



Cheers
Steve

Thanks for sharing, this is what I was looking for. The more reading i do on the heat pumps the more I like them, it's defiantly the way to go in my area, with the cost of propane and the boiler itself it would be stupid not to go this route. My buddy just paid a bit less for his nat gas boiler then what I would pay for a heat pump and his gas bills are much more than I would pay to power a heat pump.

As far as the solar idea, it's worth looking into, this will give me something else to research. I have seen a few up in the Jackson area, might be worth looking into.

Thanks all.

 

[anthony666]

this is the time of year that you could really use solar, it's also the time of year my phone is ringing off the hook with calls asking why their dhw solar systems aren't operational .. freeze protection mode

 

[backintheday]

Any pointers on a DIY solar system?

 

[theoldwizard1]

I don't want any kind of forced air in the shop, the more i read about the geothermal heat pumps the more I like them.

Do you want cooling ? If yes, then some type of forced air is necessary.

Even if you don't want cooling, the most common inside source of heating (and cooling) for a heat pump is a forced air unit.

I suggest you read some of the documentation on the Mitsubishi website. They seem to be "leading" the rest of the industry in the new "inverter" technology heat pumps (typically these are NOT geothermal, but it will give you background on what heat pumps can do).

 

[theoldwizard1]

... My shop is 3600 sq ft, R40 ceiling, R25 walls and 2"XPS under and around the 5"
slab. So I am well insulated. I have pex in the floor for radiant heating but did not install the heat source ...

What are you planning on for heat source ?

 

[stingry]

What are you planning on for heat source ?

Takagi tankless water heater, nat gas.

Cheers
Steve

 

[theoldwizard1]

I don't want any kind of forced air in the shop, the more i read about the geothermal heat pumps the more I like them.

I just re-read this thread and need to add another comment.

Radiant heat (in floor), regardless of the heat source, is not always the best solution. Radiant heat does not handled big swings in temperature well. You don't want to turn the heat down much at night because it will take too long to recover. Also, opening a door (especially a large door), will cool the air quickly and even though the floor will be warm, it will take some time for the air temp to recover.

Ceiling fans will help distribute/mix the hot and cold air.


Keep doing your research ! Geothermal heat pumps, although expensive to install, are the most cost effective way to heat and cool especially when electricity is pretty much you only choice.

Last, plan on a generator or design a system that uses anti-freeze (NOT ethylene glycol) . If the power goes out for 24 hours and you don't have a backup everything will freeze solid.

 

[stingry]

Last, plan on a generator or design a system that uses anti-freeze (NOT ethylene glycol) . If the power goes out for 24 hours and you don't have a backup everything will freeze solid.[/QUOTE]

I do not believe this to be true. As I said in my post above, my slab temp has not been below 47 degrees all winter. Possibly in climates colder than mine or in sub-zero temps, the piping above the slab may be in danger of freezing if the slab cannot radiate enough heat to keep the air temp above freezing. The coldest my air temp has been is 35 degrees and that was during a -20 degree F night but bounced back up when the temp raised above zero. I will be using an open radiant system and obviously will not use antifreeze. I will have backup heat in my utility room where the water heater and the piping manifolds are.

Cheers
Steve

 

[theoldwizard1]

The coldest my air temp has been is 35 degrees and that was during a -20 degree F night but bounced back up when the temp raised above zero.

Very impressive !

 

[backintheday]

I just re-read this thread and need to add another comment.

Radiant heat (in floor), regardless of the heat source, is not always the best solution. Radiant heat does not handled big swings in temperature well. You don't want to turn the heat down much at night because it will take too long to recover. Also, opening a door (especially a large door), will cool the air quickly and even though the floor will be warm, it will take some time for the air temp to recover.

Ceiling fans will help distribute/mix the hot and cold air.


Keep doing your research ! Geothermal heat pumps, although expensive to install, are the most cost effective way to heat and cool especially when electricity is pretty much you only choice.

Last, plan on a generator or design a system that uses anti-freeze (NOT ethylene glycol) . If the power goes out for 24 hours and you don't have a backup everything will freeze solid.

All good points. I plan on having a wood stove for the big temperature swings plus I do a lot of metal work so I will have ventilation going. And yes I will have several ceiling fans going as well. I'm almost positive I'm going with geothermal. As things progress I'll keep ya'll informed.

Thanks again

 

[Caterpillar Cowboy]

I'm gonna tag this to see how this goes. This is my first form about geothermal heating read in a garage/shop type setting and I've already learned a ton. Not sure where you're from backintheday, but here in a couple of years I hope to put up a garage with an attatched house either in Lincoln or Sublette county. Looking at something sizable to fit a shop and apartment in, and don't want to get bankrupted trying to keep the place warm.

This geothermal heat sounds like the way to go, but as you know our weather around these parts can change an engineer's opinion of 'Normal' in a hurry!