Newbie with a weird heating pier idea

[alchemy]

First time poster here, but I'm a frequent on the HAMB. Finally going to build my new shop and I am researching a weird idea a local guy used in his. He says he hardly ever needs to run his furnace in his large Morton building, and we are in the middle of Iowa.

He told me he had his concrete man dig several 3 or 4 foot piers evenly spaced around the garage floor, and filled these with concrete when pouring the floor. Sure it costs quite a bit more, but if I pay the gas company less, it may be worth it.

I am building a 30 by 40 garage with an upstairs loft, 2 by 6 construction fully insulated. Probably have forced air heat in the lower level and none upstairs.

Has anybody else heard of this method? What is it called? Can you direct me to a source of guidelines for sizing my piers? How many, how big around, how deep? Any need for foam board under the rest of the slab?

 

[joe_padavano]

Is this supposed to be some sort of geothermal system? How deep are the piers? I would think that copper or some similar conductive material would work a lot better than concrete.

 

[alchemy]

Yes, a geothermal heat sink. I don't remember the depth of the piers, and the guy who told me about it has moved out of town.

He explained it as the piers pulling the heat from the ground, in the same fashion as a regular geothermal system would with the liquid being pumped around.

 

[pseudorealityx]

He probably moved to some beachfront property in Iowa....

 

[kmacht]

My deck on the back of my house has about a dozen piers 4' deep into the ground. Surprisingly my deck isn't any warmer and the snow doesn't melt any faster around the piers than it does on the ground around them.

I think someone was pulling your leg on this one.

Keith

 

[rsanter]

Once you get around 5 ft below ground the ground temp becomes very stable. Thie would work or help in theory but if they are only 3-4 ft deep I am suspicious as you would need a sufficient surface area for the concrete to adsorb the heat or cool and be able to transfer it to the slab.
I did hear of a system where a guy put a bunch of HDPE tubing in the ground 6 or so feet down and then covered it up and built the building on top of it. They put pex tubing in the slab and use a small pump to move the fluid through the system to try to maintain an even temp in the slab. This is far more likely to work than the other

Bob

 

[jonzer12]

IMHO its all bull, the amount of surface area, deep in the ground below the frost line where it counts is minimal. On top of that you would now have a large amount of concrete completely un insulated from the ground. Take that savings from all that wasted concrete and spend it on insulation. Remember going thermal involves a large area, even if you could magically get a heat pump effect of those "piers" you would exhaust the energy stored there in short order.

 

[djb2]

How much more thermally conductive is the concrete than the soil under the slab? Probably not much.

You are better off insulating the foundation perimeter with foam.

 

[stingry]

How much more thermally conductive is the concrete than the soil under the slab? Probably not much.
Dry sand, considerably less, wet high organic matter soil, more. But basically about the same so I can't see how you gain much by having the piers!!

You are better off insulating the foundation perimeter with foam.

Yes! spend the money on insulation, both around the perimeter and in the walls and ceiling. To the OP, my shop is located in western Nebraska so the climate is probably comparable, except for the humidity. I have R50 ceilings and R25 walls with 2" EPS slab perimeter insulation. Last winter the soil just under the slab stayed a constant 47 degrees. Basically the air temp stayed at about that, warming in the day from the sunshine and cooling off a little at night. It never froze inside. The coldest it got was 37 degrees when the outside temp dropped to -20 degrees.

Cheers
Steve

 

[James-W]

I don't see how what you describe could possibly work to heat your garage. There is no doubt that geothermal works, but the initial cost to get it installed and working is quite high. Personally, I don't think geothermal for individual homeowners is a practical way to heat a home or garage because the payback time (difficult to determine accurately due to many factors) is such a long time, although I am sure other members here would disagree with me on that.

Anyway, not to be a "Doubting Thomas" and rain on your parade, but I just don't think doing what you described is going to do much of anything in-so-far as heating your garage in the Winter is concerned. In my opinion you would be spending a substantial amount of money on something that will do very little, if it does anything at all, towards heating your garage. I think you would be much better off long term with more/better insulation and a super high efficiency natural gas heater.