Is it possible, or efficient, to put a flat coil system (or DX system) inside of the footprint of a building?

I have a warehouse roughly 60x100' in RI. The building is basically on the lot lines on all sides, but there is a 7' deep basement, unfinished and unneeded space that I am planning to have backfilled and poured with concrete slab to up the weight rating of the 1st floor. Is this an application where geothermal might work, put in place prior to backfilling at 5' - 7' depth? Is it impractical to place systems inside the foundation? I found one post on here that mentioned that loops should not be to close to the foundation to avoid freezing it, but it seems that I might have ample space to place a system while staying a reasonable distance from the foundation. Since its not filled yet, insulating the foundation from the inside could also be an option.

This is certainly an interesting proposition. I do not think the 60x100 footprint is big enough to suport the load above in a horizontal application, but the thought of inside the perimeter dx or even loops down through the floor and back filled later is certainly worth exploring with some local geo talent. Keep us posted.
Eric

I think putting loops under a building foundation is very different from putting them within the foundation.
How do we get the existing basement walls to let surrounding heat migrate to the ground loops, faster than existing floor gives up heat to the newly back filled basement that loops have cooled?
Some municipalities will let you dig a heating/irrigation well and discharge into a storm sewer.
Good Luck,
Joe

Could be a good idea. DX may be easiest. Vertical boreholes would likely be required.

How would you get a drill rig in there?

If you can't it may still be possible with a drill rig that can tilt its boom off axis and be 'extended' into the basement through a large enough opening through the foundation, such as a garage door. Then all the boreholes could be drilled in a radial, (30°) off-axis pattern.

In-floor radiant may be the most efficient way to heat the basement since you're planning to pour a slab.


SR

My 2 cents. I recall a thread that mentioned ground heaving during freezing. Without formal written assurance from an expert that this couldn't happen (or wouldn't cause problems if it did happen), I wouldn't even consider doing this.

My 2 cents. I recall a thread that mentioned ground heaving during freezing. Without formal written assurance from an expert that this couldn't happen (or wouldn't cause problems if it did happen), I wouldn't even consider doing this.

I live & work in Montreal Canada as an accredited geothermal installer & designer. Our winter design temperature is -7°F. This is a common practice and in a properly designed and installed system should not cause any problem.

SR

Posted By fsq4cw on 11 Jun 2010 12:52 AM

I live & work in Montreal Canada as an accredited geothermal installer & designer. Our winter design temperature is -7°F. This is a common practice and in a properly designed and installed system should not cause any problem.

SR

Would you tell us about the precautions that are taken?  Is there a guarantee regarding structural damage?  Please enlighten us.  Thanks 

Edit: First let me make sure I understand the OP correctly.  When you say "...put in place prior to backfilling..." I assume you mean horizontal loops that are laid out on the floor, and then backfilled over it?  If so SR, is this a common practice?  I have read that vertical loops can be done under a structure.

That's just it OP is talking about horizontals within the foundation. Verticals have been done under a building (outside the foundation) without impact (I'm aware of).
j

Would you tell us about the precautions that are taken?  Is there a guarantee regarding structural damage?

As mentioned previously, the system has to be properly designed and installed. That means accurate load calcs done using recognized methods or software, a ground heat exchanger of sufficient size, depth, spacing, insulating, and proper grouting methods to ensure the ground will not freeze - even if it runs continuously.

If you want ironclad written guarantees, no problem, just pony up with a cheque for in-situ ground conductivity testing and engineering studies signed off on and stamped by a PE; if not, simple, don’t do it and install something else.

Regarding horizontal ground loops within the foundation, I doubt there is sufficient space (in this case) to make this practical which is why I suggested DX with 30° off-axis radial drilling - if even that’s possible.

SR

I think some basic construction parameters would rule out laying tubing on the floor as you would eventually draw the frost line under the buildings foundation .. as far as drilled dx go for it, just insulate the 1st  12 to 15' as you normally would and grout ...   We always insulate pipe within 12 to 15' of foundation as we are in n IL and i have repaired frozen water mains below 5'. Not to say if you were on bedrock or had water running thru the foundation it wouldn't work but u would have some details to work thru..

Very interesting idea, and problem to solve, and, don't know anything about this! Two questions and one comment come to mind: (1) Untimately the ground source energy is comming from the sun, and your field is 100% under roof. Is this significant? (2) Drilling horizontal, or 30 deg down... does this take you across the bounderies of your property? Don't know who would care, but I'm sure somebody does, and, this is pemissable without a variance, permission from a neighbor and ammendment to the neighbors deed, etc. Something! The freezing issue is a significant consideration, which can be dealt with by design considerations and safety controls to never let it freeze. This of course, limits capacity in heating mode, but I believe this would be required.