Geothermal and radiant

[danreed76]

Getting ready to finally dig the foundation for our new house  8) and finishing up the plans for the stuff that can't be effectively retrofitted later.  One of the things we want to do is install radiant heat in the basement and first floor, but we're also considering geothermal.  I've drawn up the system for the radiant, planning on using a water to water heat pump.  Is there any reason I can't use the same system (with the appropriate valving) to shift it over to cooling, feeding water cooled fan coil units?

The house is going to be very well insulated, and I'm also considering adding a large water tank to the system for storing hot (or cold) water to minimize the run cycles and get the most "full load" run time on the unit.  So... is it doable?  Most HVAC guys seem to want to sell me on 2 forced air packages (split units), and abandoning the radiant.

[beenthere]

dan
Am I reading that right, that you are asking about running cold (cool) water through the radiant heat pipes?

Am thinking if so, that you may end up with sweaty and slippery floors when moisture condenses there. ??

[OneWithWood]

I am thinking the same as Beenthere on the condesation part.

[danreed76]

Thanks for the questions.
I guess I should have been clearer with the description.  In the summer time, the water would shift to running through fan coil units (small air handlers)in each zone for air conditioning.  For sure in our part of the country we couldn't use the radiant piping for cooling.  I think the dew point in the summertime can be over 90 degrees F.

I put a schematic together, I just need to get it from .dwg into a format I can post.

Dan

[Holmes]

 I believe what you are asking is correct you can use the same system  You must make certain your fan coil units are designed to do the job with water at 55* temp, no way near as cold as an AC system coolant. I do not do AC work but I was on a job a few years ago that had h2o cooling. It did not work and after 3 years they took the system out and put in mini split ac units.

[maurice-r]

Let me say up front that I am not an hvac service tech (even tho I hold a licence in this city) (to explain, I work on refrigeration) nor do I do geo.  I AM a homeowner who has been studying up on what to do for our house. 

I've been seeing some recent articles in trade magazines about radiant cooling.  Been seeing a lot on geo for quite a long time.  I don't have all the reference links, but each of these publications are free to people in the trades and each has thier magazine on their website for archiving.  This is not an endorsement to actually buy anything from them.  www.contractormag.com  www.phcnews.com  www.pmmag.com   Also look up John Siegenthaler, P.E.  He has an excellent textbook and a website, and writes for PM magazine.

I also had concerns about dewpoints and cooling.  From the reading I see, it is possible to use the same radiant loops in floors, cielings, and/or walls to cool with as long as the controls can calculate dewpoints.  I've also read that at times one may also need more cooling than the "dewpoint controlled" radiant can do.

Ys, I've read lots of cooling involving geo and fan coil units.

You might look at insulating UNDER your basement floor.  (And walls, in winter that is a lot of heating going to the subsoil.)  I've read on sprayfoam.com forums that when it is dug, a sprayfoam contractor can put down closed cell foam then you can pour concrete on it (obviously, you want the radiant tubing IN the concrete).

And to touch on another idea, I saw in the Solar Decathalon (contest sponsored by Feds with universities competing for best use of solar) that one team used liquid dessicant dehumidification then dried the dessicant using solar!  THAT might be the answer to radiant cooling dewpoint problem. 

Long post, because I want to encourage you!

[Kansas]

Take a good look at the tax aspect of it. I got a nice tax credit when I put in geothermal 3 years ago. I don't know if that, or any other, is available. Nor do I know what all it goes to, if there is. There were tax credits on the windows too. If you are spraying foam insulation on basement walls and such, I don't know. If you have a good tax accountant, you might ask. It might influence your decisions.

[Al_Smith]

A little late on this but a thought to ponder .Some of the old geo thermal units ,Tetco for example used a large A coil with just cold water for cooling and they worked just fine if  you have a source of cold water such as a well or a very deep pond .They didn't however circulate water under the floor but rather used conventional air handling  units .Because the air passed over a basically cold coil they would dehumidify .

Fact being I work in a rather large automotive engine plant of over 2 million square feet of which approx 750 thousand square feet is  cooled by a straight water coil geo system so it does work .You have to move a lot of water though if done without refridgeration .There's  charts on it if you do a "google "