Geo Loop under House?

singh

had directed me to this company in Colorado.

The three ton system is under house.
Alot of care however is still needed to install these loops.


http://www.geothermal-dd.com/gdd/Projects.html





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singh

Does any one have a comment , about earth sheltered type home being dug into side of hill. Since a lot of excavation going on, maybe option of installing horizontal ground loops under heavy insulated slab. Foundation 140' long 40' wide.
Radiant tubing in slab.

Me thinks , soil will always stay warm and wont freeze up, but at the same time pull heat away radiant.




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[Deleted User]

horizontal ground loops?

for geo heat pump?

A.J.

ground loops

If I remember my class on loop design you could have frost problems if you don't keep it far enough away and don't have a proper sized loop. You are also for argument sake not going to be able to get at it after the house is up.Sound to risky for me.

BC_3

Not a good idea...

Even though it is called "geothermal", virtually all the heat coming from the ground is actually a combination of solar and heat storage(depending how much AC you run), especially on a horizontal loop - only a few percent of the heat actually comes from heat flow from the deep earth. Unless your AC load is very large, you NEED that sunlight and rainwater to recharge the field.

Also when the ground freezes in the winter it is liable to cause issues with the foundation (frost heaves)!

[Deleted User]

What about the caisson...

I'm going to have to drill a whole bunch of holes for my new mountain retirement home (Hydronica) and am seriously considering dropping some 3/4" PEX into the bore hole to take advantage of the earths heat.

Unless of course, someone (geotechnical engineer or structural engineer) talks me out of it...


ME

[Deleted User]

Hydronica?

love the name, but from the little research that i've done, and being on site during the renovation of a, money's not an issue mansion, and it's 7 wells for their geo, it takes some math and a lot of pipe or wells to match the heat pumps

Tom Hopkins

Yes, it's possible

We did a design, being built now, for a Library building with a large underground parkade. Lots of free excavation and we pinned slinky coils to the sidewalls of the 20 foot excavation as well as a whole series of flat slinkies under the parkade slab on grade. The trick is doing a balanced load on the field so you don't need to drive it down to freezing temps for heating mode, nor do you reject a lot of heat into it during cooling mode, and possibly heat up the parkade by late summer.

One has to be very careful about specific local conditions. In our case we had wet subgrade soil, and a building heating and cooling load profile that was fairly balanced. Supplemental heating from a local district energy loop as well as 120 sq.M of solar heating panels on the roof provide the base heating loads and ventilation load during the winter (even with a couple DOAS HRV's on the roof). We are also running a higher flow/lower delta T in the geo-exchange loops to minimize the peak cooling season heat rise in the ground loops. We are also using a number of in-ground tempertaure sensors to monitor the ground temperatures over the seasons to make sure that the system stays within specifications.

A ground coupled house with a well insulated exposed envelope, and good windows with very small heating and cooling loads can easily be served by flat slinky geo-exchange loops run under the excavated areas of the house as long as the soil conditions are known (soil conductivity checked), and the slinky coils are insulated away from the house and direct contact with the soil is maintained (no putting the slinkies in drainage gravel sub-grade layers!).

The key is minimizing the house loads, running the geo field for higher flows to get smaller delta T, and carefully balancing the load into the geo field. If the house envelope is done right, the biggest load becomes domestic hot water heating, for which you'll need supplemental heating anyway to get the 140F temps for that. Most water to water heat pumps with a geo-exchange system are hard pressed to provide 120F heated water efficiently over normal operating ranges. A storage tank and buffer tank will likely be needed to prevent short cycling of the heat pump during light load conditions.

Tom Hopkins

Caissons

Thats a system that has been used in Europe and now in Canada - check out "Enercret" at these weblinks:

http://www.geothermie.at/page/index2.html

http://www.construction.com/NewsCenter/Headlines/ENR/20031013e.asp

http://www.geothermie.at/image/deutsch/download/english/beschreibungen/enercret_thermo_active_foundations_system_description.pdf

GMcD

Care and Attention

The real issues are to reduce the heating (and cooling) loads down as far as possible - which reduces the amount of geo-exchange one needs. And then design the geo-exchange loops and balance the energy load with the house heating/cooling loads so you DON"T need to drive the ground source loop temps down very much in heating mode, nor push too much heat into the ground during cooling mode. In a heating dominated climate, that's the challenge- many folks drive the geo loops down to freezing temps to extract heat delta-T from the ground, but how well that performs is all subject to the soil conditions, depth of bury, and other details that rules of thumbs and "standard approaches" don't allow for.