A geothermal system will be at least 300% efficient when heating the water for your radiant system. Any thing else you do will be less than 90% efficient. It might take you 7 years or so to recoup your costs, but geo will always cost less to operate than anything else.

I was just about to post a very similar question involving remarkably similar variables. I am building a 2100 sq ft SIPS home in the mountains of Colorado . I have spent the last few days searching through these forums in a attempt to figure out the most cost and energy efficient way to heat the home (we don't need any A/C at 9000 ft!). At first I was convinced that radiant floor was the way to go, due to comfort and efficiency.. Then I started to learn that SIPS are so well sealed and insulated, that forced air can heat the house just as efficiently and will cost much less to install. It then might be better to take that savings and put it towards triple pain windows and a geothermal system. Also, SIPS are so tight that the house would require duct work for an HRV system anyway. In addition, geo in a tight SIPS house might cost less because the system can be smaller. I then got concerned about comfort of radiant vs. forced air, and learned that a geo system is more comfortable than a traditional gas furnace because there is no combustion, and greater amounts of warm air is consistently being circulated throughout the house.

That being said, I actually don't have any real experience in regards to any of this. This is just information I've gathered reading through these forms. However, I don't feel like the issue has been properly addressed when you factor in the tightness and insulation of a SIPS house. Can someone with experience please comment? I'm not sure exactly where Dave3 lives in CO, but keep in mind that I live at 9000 ft and winters are very long and very cold.

I would agree with  1) and 2) above.  There is a combo heat pump available that will heat both air and water.  This works well if you have a few areas where you really want a warm floor .

Markdrucker,

With geothermal in a tight home in a cold region, you may need a humidifier unless you enjoy heated air with a relative humidity of 35%.

A well insulated , tightly constructed home will decrease the heat loss there by decreasing the size and cost of the geo system required to heat it . shouldnt effect your ROI that much . Second point on the ac. the air conditioning eff of geo systems is great but compared to other high end air to air systems , the savings are not huge. In heating domonate regions the time to recoupe your investment is much less then in cooling domonante areas . And for the 1 week a year you might want it youll be the most popular guy on the street. sorry about all the misspellings my spell check isnt working

Just my opionon

I think there's a fallacy of thinking out there that radiant is any more efficient than forced air. It just isn't so. Especially with geo.

With the cost of pumping the water, and piping loss on the heat load, there is no way that radiant is any more efficient than forced air. Instead, forced air is more efficient.

On the comfort side of radiant... My dad finished his house about 2 years ago now. He built it from footing to roof with ICFs. It is a TIGHT, 5,200 sq. ft. house. It requires 4 tons of geo for radiant heating, forced air cooling, and priority domestic hot water heating, all from the same unit. He didn't see as big of a problem with it when he did it, but he put in a 5 ton EarthLinked DX system. Anyway, the house is tight.

Right now, he uses his forced air system for the house. It's WAY more comfortable and efficient than the stupid radiant floor. We've been RPA certified, trained, etc. with radiant floor systems, and have installed many.

We installed his radiant thinking that you just can't beat the comfort, and that it would be more efficient. HA! What a joke. Maybe that's the case in a draftier house, but not in his. The biggest problem is that the system over-shoots what's needed when family is there, or when the oven has been used. Radiant can't act fast enough to mitigate the problem. The forced air from the geo is so much more comfortable because it can be set at 'auto-change over'. He can set the temp. and leave it alone. If it needs cooling, it'll cool. If it needs heat, it heats.

On the efficiency... He has his system sub-metered so that we can show people how efficient the system is. His COP for radiant averages at about 3.8. For forced air, it averages 4.7. There's just no comparison. It costs money to run those pumps.

nyway... both of you, Dave3 and MarkDrucker, would be best off with geo in the long run--and I'd definitely recommend forced air over radiant, if comfort and efficiency are your issues. (cost should be, too)

A side note... he has no HRV, either. The attic is icynene foam insulated, and there has been NO problem without an HRV in our arid, HOT, COLD climate in Northeastern Utah (keyword, arid).