I stumbled onto the forum last week, and have been lurking ever since.  It is a fantastic resoruce, and I have gotten soemwhat up to speed on geothermal in record time.  This is my first post.

I will be starting construction of my 2500 sq ft house this Spring.  I live in central New Hampshire.  Prior to giving serious consideration to geothermal, I was exploring the feasibility of an indoor wood gasification boiler as a way to avoid the pitfalls of fossil fuel systems.  Becasue it is a boiler, I was all set with using hydronic radiant floors throught my house, including a loop for the garage to keep it at about 50 deg and radiant in the walkout basement slab.  Because of the expense, I was going to pass on central AC, and probably use a couple of window units.

Now that I am exploring the possibility of using geothermal, my certainty of going with hydronic floor radiant is quite shaky.  If money were no object (and it definitely is a consideration...just doing geothermal is stretching me WAY past the point of comfort), I would probably do some kind of split system.  But unless I hear differently, that seems like a very costly option.

If one were to completely discount cooling, how well does geothermal meld with radiant?  For example, the mix of a boiler with radiant is perfect.  Is there anything inherent in the heat pump process that makes it more or less efficient to heat a liquid, as opposed to air?

Then if one were to assume a radiant set up, how would cooling be done?  Could the same heat pump generate hot liquid and cool air?  Aside from the duct work, what would be required?

My house design is very open concept, and the summers up here are not THAT harsh.  As far as the AC component, I cannot imagine I will need extensive duct work throughout the entire house.  Perhaps some miniducts here and there would be enough to take the edge off.

I would greatly appreciate your thoughts and opinions on my situation.  Thank you very much. 

If I understand this correctly, there is no inherent higher cost of pairing geothermal with radiant.  The additional costs I have heard of come from, in essence, building two delivery systems; in-floor hydronic and air ducts for the AC.  Is this right?  Or is there an additional cost to having a heat pump that can output hot water and cool air?

Are there heat pumps that are water to water, AND water to air?  How would this be accomplished?

Thanks agains for your help.

Hot Water Combination
Forced air and hot water heating units from 1.5 to 6 tons.
These units are ideally suited for heating all or part of your structure with radiant floors and heating portions with forced air (if you choose), and cooling the entire structure with DX forced air. Unlike some combination equipment on the market, this unit has been around long enough to have the "bugs" worked out. The Hydron Combination is probably the best designed and most reliable equipment of its kind.

Nick,

If I have it right from one of your earlier post, cost was a major concern and maybe a deal breaker to go or not to geothermal.  If this is still the case, in my opinion, going with a water to air system or maybe a DX to air would most likely cost you the least to get into geothermal apposed to having to use a more conventional heating/cooling system.  The main problem when it comes to cost, the hydronic system will add up quickly with the pumps, lines, buffer tank and valving, compared to air system, which you would need for cooling even with hydronics.

If you go with water to air, you could still put tubing in the floors for future upgrade to a hydronic system.

The bottom line in my opinion, you would be better off going for the lowest cost up front geothermal system compared to going to a more conventional heating system.  With the savings you will get, put money away to upgrade to hydronics in the future.

Regards,