I see radiant floor heat seems to be popular, and I like the idea of warm floors in the winter, (I'll lay on the floor rather than a couch when watching TV). I hear that you can cool as well as heat with geothermal. I'm not a big fan of AC. I'll run my window AC 5-10 nights/year– only when it's sooo humid I can't sleep. It would be nice to flip a switch and cool the house on those nights. The cooling systems I've seen for geothermal use hot air to heat and the same ducts to cool in the summer. Can you use geothermal to cool with the in-floor PEX tubing? Would that make the floors cold in summer? Are there condensation problems if you do? Is one more efficient than the other?

Hi, we are in NC are y ou from the far noth. We just completed a geothermal DX system in our 100+ year-old home. Geothermal is efficient for both heating and cooling. It is quiet and all the equipment can be placed inside (basement, crawl, attic) out of the weather extending the life of your eq uipment. A system can be designed to help with humidity.

Our system uses copper tubing filled with a refrigerant that goes into the ground on a diagonal about 75 ft x2 per ton. No wa ter p ipe problems. You can run the DX to heat at night and to cool for the day. I think you can get just a heat system. I am confused do you want to use your radiant heating for cooling. A friend just installed a geothermal system (water) with radiant floor piping. and duct for AC He loves it. PEX is used.Your floors should be a fine temp to lay on.

Joe Parsons VAp of sales can be reached via the website. He is excellent.

Just let me know if I can email you any info on the advantages of DX
http://www.oikos.com/esb/53/hydroniccool.html might help
They might try to sell you something, but it is a start.

If no expert gets back to you, Go to earthlinked.com. and ask about using the pex for both.

Coco

Radiant heat works well...radiant cooling not so well. No dehumidification with radiant cooling. Yes condensation on the floor is one of the drawbacks.

OK, so it seems the way to go is radiant floor heat in the winter, open the windows in the summer, possibly a whole house fan. Then if I find I need AC I can install one of those units that sit outside and a tube runs through the wall to a vent/control panel on the wall for the bedroom.

Or if I think central air is the way to go, that can run off the geothermal as well.

There are heat pumps that will make hot water for radiant and do forced air heating and cooling as well.

In theory yes, but you have to remember that Heat goes up and Cold goes down. Thus radiant floors are good for heating, but not for cooling. Perhaps Radiant ceilings? Interesting idea. This still wouldn't solve the condensation problems. your better off just sticking with duct work for cooling.
 

Heat does not go up and cool does not go down.

Heat transfers in ANY direction, or radiant heat wouldn't exist. Hot air rises, and cold air falls. Hot water rises, and cool water falls. A hot fire can be felt to the side of it via its radiant heat characteristics. You can broil meat in your oven, from above, because of the radiant heat from the burner.

The natural body climate wants the feet warm and the head cool. Thus it becomes more comfortable to heat the feet and cool the head. Radiant floor heat heats the feet and objects. This is part of what makes it so comfortable.

One option I would suggest is the radiant ceiling from bekausa.com. They use a capillary tube system in the ceiling. It both heats and cools. Then you don't have to worry about floor coverings, beefing up the floor to hold the weight of concrete or gypcrete, and you get cooling out of it that's comfortable, too.

A radiant chilled floor is uncomfortable. My dad has run his that way in the past, and we don't like it.

Dewayne is right. There are heat pumps that heat water for hydronic heating, and they heat and cool air, too. EarthLinked's system can be set up this way using their SW model unit.

One thing, as I've noted in other threads, is that forced air geothermal, when designed properly, will be VERY comfortable. It's also not near as expensive as a radiant floor or ceiling. Because of geothermal's lower supply heating temps, the air will more evenly mix and distribute in the home. Just make sure your installer sizes, designs, and installs the duct work correctly, and you can't go wrong. Radiant floors cost more to install AND to operate than forced air systems. Anyway... Keep us posted.

Hi tuffluckdriller, Excellent post, but I'm confused as to why you believe that radiant floor cost more to operate? Could you explain this in a little more detail? Thanks, Eric D

Radiant floor, with geothermal, costs more to operate because of the lower COPs when heating water, and the cost of running the pumps for the floor.

Some claim that the fan in a forced air system uses just as much power as the pumps in a radiant system, but that's not what we've seen in the field. Both my dad and uncle have radiant systems and forced air. They both have sub meters on their heat pumps to see the cost of operation. My uncle checks his daily. With forced air, he's approx. 40% more efficient than with the radiant.

Radiant does have its place for comfort, but it does not operate more efficiently with geothermal. Check the COP with any water to water, or DX to water heat pump vs. the same model/size with the same loop for forced air COPs.

I'm not sure wqhat kind of pumps you're running in those radiant installations, but a well-designed radiant system shouldn't need more than 90-100W worth of circualtor pumps to run a good sized house. If you design the system with pumping requirements in mind you can drive it even lower - check out some of John Siegenthaler's recent articles. Now the circulators for the hydronic side of the heat pump are a different matter - if your heat exchangers are undersized like mine are you do need a hefty pump - Mine are a bit over 300W on the hydronic side. That's a manufacturer dependent thing, though - many hydronic heat pumps only need a fraction of this. Either way, that's got to be a lot less than a 3/4 ot 1hp blower motor.

As for lower COPs for hydronic heat pumps, I'll concede that you're probably correct that most radiant geothermal installations operate at relatively low COPs. However, this is generally not due to any inherent disadvantage of hydronics, but non-optimal controls and radiant design. At 120F water temp, most heat pumps probably have a COP around 3-3.5 depending on loop temp. From what I've seen, many installers just set the aquastat on the buffer tank to 115 or 120F and leave it, so this is what these installations run at all season. The proper way to do it is to control the water temperature with an outdoor reset control so that it is always at the bare minimum required to heat the house. If the house needs 120F water at a design temp of zero, when it is 35F outside, it will only need 95F water. At 95F output temperature, the COP will be more in the 4.5-5 range. If your system takes advantage of this the seasonal COP will be closer to 4 than 3.

Obviously the other big thing is to design your radiant system to run at a very low water temperature. This isn't always possible in retrofit situations, but in new construction it should be relatively easy to keep water temps close to 100F at design temp. If you can do this and couple it with reset control, the resulting system will beat the pants off just about any forced air system for efficiency.

So to summarize, the average forced air installation may be more efficient than the average hydronic installation, but if you optimize both, I think radiant wins, or at the very least ties.

 

John Siegenthaler is one we've followed faithfully, too. His articles have been pretty good, until he brought up the point that a propane boiler is more efficient than geothermal. What!?!?!

Anyway, I agree with the outdoor reset control on a radiant system, to a certain point. Radiant floors are almost too slow to react to temperature changes when you're only dealing with a 95-110 deg. supply range, anyway.

At a max. temp of 100 deg., a geothermal water heating unit will have a higher COP than with 120 deg., too. However, even at the 100 deg. mark, the COPs are significantly lower than forced air.

One thing that's underlying in my bias against radiant floor systems, too, is the installed price anyway. Too many times people want a bid for radiant floor with geothermal. Most of them want cooling, too, and that's just doubling the system. They end up with 2 heating systems in the house. The price to install the doubled system is enormously more than just one of the two.

What seems to happen, then, is a sticker shock. People can't believe we have the nerve to present them with such a high price. How dare we do that. They don't care that it's 2 systems. They don't care that it takes more design, layout, install time... they just want the radiant floor at a normal forced air price. When they see the high price, they automatically blame the geothermal system for being the culprit. Too many times it seems that they won't even give geothermal a chance after that. They've lived in their houses with crappy duct and furnace design that has left them cold/drafty/uncomfortable, and they're convinced that the only solution is a radiant floor. However, they don't want to pay for it.

Then, look at that huge amount more for the radiant vs. just forced air. For what benefit? To be less efficient; less reactive; less comfortable in spring and fall (during the transition times); have that warm floor in the cold winter (which isn't necessarily bad, it just has a high price for the benefit); even temps in the home...

I have to reiterate that a properly designed duct system, especially with geothermal, is wonderfully comfortable. There will be no drafts, no noise, and even temperatures in the home. Anyway, I don't mean to be in a debate on this, it's just my opinion that radiant has duped a lot of people that it's more efficient than forced air, and we've seen otherwise.

I'll agree with Cyngeo that a properly designed radiant system, both in terms of pumping loss and water temps, should have efficiency competitive with forced air. From what I hear and read, radiant often allows same comfort at significantly lower thermostat settings, thereby reducing building load and operating cost even if COP is similar.

On the flip side, I would also add that a properly designed duct system allows an ECM blower to move design CFM at a wattage well below that suggested by nominal motor horsepower. My nominal 1/2 HP ECM blower on my 3 ton Envision draws between .3 and .7 amps under nearly all conditions, in other words 75-150 watts

Wow, where did you see that comment about propane being more efficient? Siggy has always been a proponent of geo systems as far as I can tell and has a really good overview in his hydronics book.

Are you sure about COPs being lower for hydronic units at 100F? Granted I didn't go through all the manufacturers' specs, but a quick survey indicated that for the most part they were about equal. I believe the ARI standard rating for hydronic units is at 104F entering hydronic temp, which is around 115F leaving temp for most units. COPs seem to be in the 3-3.5 range for this condition for most of the ones I looked at. At 95-100F leaving temp they seemed to be 4-4.5 which is competitive with most forced air units at 32F loop temp, right? The best of the forced air units might be a little better since it seems like the vast majority of development effort goes into this side due to the relative volumes.

Radiant systems do tend to be expensive, and with a geo system will probably never pay off in efficiency. Even with a traditional fossil fuel system the efficiency gains are, as you say, overstated. the most common argument in favor of radiant is that you can keep the house temperature a few degrees cooler and still be comfortable. From my experience this is somewhat true, but I've never seen a good study on the subject with quantitative results. Even if you can keep the house at 66F instead of 70F, it's not that large a gain. I do think radiant can be price competitive when applied to a retrofit situation where there is no existing ductwork and AC is not needed but this is pretty rare.

I think we're going to have to agree to disagree about relative comfort - I suspect it might be a regional thing. I grew up in New England, where forced air systems aren't as dominant and tend to be in low-end homes. I don't think I've ever been in a house with forced air that wasn't drafty, noisy, or both. I know that properly designed forced air systems can be comfortable, especially when coupled with a heat pump; but at least in my area contractors who are able and willing to design a such a system are a rarity. Unfortunately I suspect you and most of the other contractors on this board are on a completely different level than most of the installers around here. Again, this is probably somewhat regional - areas that have more AC use and a longer history with forced air would naturally tend to have more competent contractors and better designed systems.

I think we're both almost on the same page - would you agree that an average forced air geo system is more efficicient (and a lot cheaper) than an average radiant system, while an average radiant system is more comfortable than an average forced air system (I'm talking about a typical builder installed system, not one of yours)? Similarly, a well-designed forced air system can approach a radiant system for comfort while a well-designed radiant system can have similar efficeincy to a forced air system. I personally believe radiant systems have many advantages over forced air. Are they worth the cost premium? I think that's really up to the indvidual.

That's pretty impressive power use - I had no idea the ECM blowers were so good. How many CFM is that moving? I think the words "properly designed system" are key for both forced air and hydronic systems. I see lots of radiant systems with a big circulator pump on each zone that probably use close to 1kW when they're all running when a single 75W circ would more than suffice.

I don't have the spec in front of me, but when the system is in 'fan' mode, lowest speed. I think it moves 600 CFM. It only sees about 0.12" WC at that flow and draws 0.3 amps. Amps ramp up to 0.7 when it is trying to move 750 CFM into a zone with fewer registers than I would have chosen had I been aware of the required airflow. (Waterfurnace docs were a year behind Envision product release)

So far I haven't needed to run the unit in high stage, but testing indicated amps in the low 1.x range moving 1200-1400 CFM into several zones at once.

ECM blowers are a huge advance in technology - I wouldn't buy, sell or willingly deal with a system without one. The three ton air handler in my old house had a conventional 3 tap PSC blower that clamp meter amped out at 5, 7 and 9 amps, respectively, though I suspect those numbers were exaggerated by abysmal power factors.

Where would I find recent articles by John Siegenthaler? I googled him and found his book.

I would definitely agree that the average installations are as you stated, cyngeo. It just seems that the installed price of a well designed forced air system will be lower than even the average radiant system.

Siegenthaler's article seems to me that it was at least a year ago, if not 2 or so. I don't really remember. Perhaps (I apologize if I did) I misspoke. Maybe it was another radiant guru. I am pretty sure it was him, though.

cyngeo
I must say being a New Englander I take some offense to your generalazation about incompotant tin knockers in our region of the country
and the comment about them being in cheap houses , the reality is cheap hack ductwork is in cheap hack houses , and quility ductwork is in quility houses
While this may be true in your region here in CT we have very strict codes on ducting and many quilified fabricators, now I not saying there arent hacks
here but just no more then any other part of the country hell you have to go to school for 2 years full time before you can hang duct legaly here