The answer to your question is YES!

I would encourage you to do the radiant in-floor for heating as this will be the most comfortable form of heating and will add the greatest resale value to your home as well as having some of the lowest operating costs which will pay off, particularly if you plan to stay in this home.

Triple function would be the way to go, forced air heating & cooling, full function (hot) water for radiant in-floor and domestic hot water. Virtually nothing else will be as efficient,versitile and flexible.

SR

Thank fwq4cw,
Another question if you don't mind. I realize that radiant floor heating is more comfortable, but is there a big energy saving with it over forced air?
I'm thinking there would be especially if the radiant tubing was in concrete as that would act as a large thermal mass holding in the heat for longer times.

Re: zick

The short answer to your question is yes; for several reasons. Water is a more efficient medium for heat transfer than air. More over, with hydronic radiant in-floor heating, water only has to be heated to a temperature in the low 80 degrees as opposed to air which would have to be heated to the high 90's at least.

Other factors would be the temperature differential between leaving and returning water temperature would be lower than that of supply and return air. So less energy would be required to heat the water than heating the air.

Radiant in-floor heating just has to heat the first few feet of air from the floor up for people and pets to be comfortable. Forced air would have to heat the entire volume of the room. Radiant also heats the entire floor surface whereas forced air heats by heating the room perimeter. Something else to consider is that because lower temperatures are required for comfort with radiant in-floor hydronic heating, there is a lower temperature differential between the air that rises to the ceiling and that of the colder air outside resulting in a lower rate of heat loss. All this coupled with the high efficiency of geothermal make this technology a winner.

One last thing, if you have a swimming pool, it is possible to use the hot water heating capacity of the HP that would heat your floors in the winter, to instead heat your pool in the summer.

One system, consolidated mechanical room, low maintenance, longest life-cycle, multiple uses, ultra high efficiency, enhanced resale value, eco-friendly - a total winner!

IMPO

SR

Re: zick

I realize I didn't answer all of your question.

A concrete floor does make for a highly efficient thermal storage mass when radiant in-floor heating is used. This thermal storage effect also makes for a quick recovery when something like a garage door is opened.

However, when a fast increase in room temperature is required when the floor is not yet warm, a triple function geothermal heat pump can provide that function with force air heating until the thermal mass of the floor catches up.

SR

I'm not an HVAC expert by far, but I've been looking into a forced air geothermal system as well. While I agree that in a slab radiant can be more efficient, this efficiency decreases when floor coverings are added. Some circumvent this problem by adding wall/baseboard radiators. Since a good portion of my house will be either carpeted or have wood floors and I want cooling as well, requiring ducting to be installed anyway, I think forced air would work better. As far as producing enough heat, the system will pump out cooler air than a typical furnace-based system, but the system would cycle longer. If the system is sized properly, there should be no problem keeping up with the heating. On two story homes, I believe it is more common to use forced air with geothermal anyway, so itÂs not like this is an untested setup.

As a caveat to my post above, I should mention that if I were building a 1 floor slab I would have the radiant installed if I could afford it. In my area, itÂs almost expected these days, and itÂs really not something IÂd want to retrofit.

Thanks guys, that helps a lot!

I would conjecture that 80%+ of the heat pumps in this country are forced air, have one myself, geothermal now 15 years old.

Another point is don't buy into something is more efficient because the Delta T (temperature rise) across the heat exchanger is smaller, e.g., the floor/water argument. Warmth in the room is dependent on the number of BTUs delivered, and the real question is "what are you paying per BTU" delivered.

Remember too, heating oil was looking at $4 a gallon about a year ago, it will come back. Electricity, e.g., a heat pump (geothermal not the only choice - the new air-to-air work at very low outside temperatures) cost has increased at a far slower rate than has heating oil. In fact at $2 a gallon and 85% heating efficiency oil heat, my electric geothermal cost less to heat my home with electricity at 15 cents per KWH. That's about what I paid this year, last year when oil was higher I was paying more like 12 cents a KWH...i.e., saved a couple grand $$ over oil heat.

I installed a WaterFurnace Synergy 3 a few years ago and have been very pleased with it. It was not very much more than a traditional HVAC system (without radiant) and the energy savings has more than paid that back in 3 years. However, I did decide to go with Radiant Heat, which as you noticed, adds considerably to the cost of a heating system. Let me tell you this -- SHOP SHOP SHOP. I got three bids around the same amount (way too high and my general contractor kept telling me that was going to be the price). I finally got one about 20% lower, then one from a guy about an hour away for HALF the price. I interviewed him (a small firm, just two brothers and a couple part-timers) and he was very knowledgeble with excellent references. I now have my radiant floors at half the original bids and I am VERY happy with them. Keep at it.

I cannot get my Geo slab up to temp on cold days I have a ten ton system running a 7800 square foot shop it has two very large doors on either side faceing East and west the floor was very well insulated and tuck taped with the exception of the two doors which total 65 feet of cement exposed
to outside when its -20c they never get it hot in the shop the lines are spaced 9 inches apart it works good when its -15 or less could this be from the exposed cement? The heatpumps are tranquility27 nextenergy units and they are tied to a 80gallon buffer tank