I'm torn with the amount of equipment that is available to heat this massive structure and which direction to go. Geo exchange heat pump, the new Pheonix Evolution looks simple, a boiler, tankless water heater? It's endless and I would love to hear your ideas of the best system to install. I only want to do this once. Maybe I should explain a little more about my system.... The ICF house is 3 levels. The 1st floor has 8 inch ICF walls 14 feet tall of which 1/2 of the wall surface area is burried in the dirt. The 2n'd floor has 8 inch walls 12 feet of which 1/3r'd of the wall surface area is burried and the rest of the ICF walls system is 6 inch concrete walls on up to the 3rd floor top plate. The entire roof/attic has 14 inch thick R48 sprayed foam open cell insulation. So the entire structure is closed. The first floor (bottom) is a 5 inch concrete slab with 2.5 inches of EPS under it. To be used as a workshop but able to be turned into a mother in law down the road. This has 4 loops of Radiant tube spaced 8 inch O.C in. (RH manifold 1) The 2’nd floor has 2 bedrooms that sit over top of the first floor (has joist heating 3 loops (RH Manifold 2) and the rest of the entire floor is a 5 inch concrete slab with 8 loops of (RH Manifold 3). Same set up, 5 inches of concrete with 2.5 inches of eps under it. The 3rd floor is all joists that has radiant tube installed with heat plates in the joist bays. 6 loops on (RH Manifold 4) and 3 loops on (RH Manifold 5) On the 2nd floor, I have a machine room that houses all the equipment. The 2nd floor will have a pellet stove that can be used for quick heat pickup that points towards the stairwell so heat can rise into the 3rd floor. We have geo exchange piping burried behind the 1st floor walls 14 feet deep on up to about 6 feet beneath the FF of the 2n'd floor. This piping is directly under the 2n'd floor concrete slab. Lain in a slinky pattern, the total of 2 loops each 500 feet are seperated by an ICF wall on each side inside the building under the 2'nd floor slab of the building. Totaling 2000 feet of geo exchange pipe. Another 500 foot loop is installed on the side of the 1st floor walls on the exterior of the building. Hope that makes sense....but let me know if you need more clarification. The geo totals 5 loops. Cooling 1.7 tons is only needed on the 3rd floor so I wanted to install an air to water slim line fan coil since the floor plan is very open. If any cooling is needed on the 2n'd floor, I'd do the same. So lets talk about what I’m looking to obtain. I would like to keep my domestic hot water separate from the radiant heating system. I would like to have the ability to use a tankless water heater as a back up to the geo thermo heat pump should I go this route, and have the ability to add solar hot water collectors and possibly in the future, an exterior boiler. This should handle the heating for this home but the equipment decisions are mind boggling. Our electricity is expensive here so propane is the most efficient heat source and may use the tankless heat source most often. Depends on how well the geo exchange heat pump works though. Other info for conditioned space would be to have an ERV for fresh air (not sure which one) but each bathroom has an exhaust fan. I would like to find a decent user friendly control system for the entire BMS as well but I'm confused here too. All our windows are vinyl Milgard Tuscany with 3 D max coatings with low e. The laod calculations have been completed and I can share them if needed. For the record, I'm not a contractor but a home owner/builder looking for the best direction so I can do the right thing for this house. Any input you have is truely appreciated I'm located in Placerville, CA at about 925 feet elevation in a canyon on the river. Thank you!

what is your load?

I don't understand where your geoexchange loops are installed.

I always prefer to exhaust bathrooms with my ERV. I know there is argument about this, but it's silly. running the ERV for a little longer to get the moisture out is definitely preferable in nearly all cases to losing all recovery on what can easily be 20%-30% of your total recovery ventilation.

Posted By NRT.Rob on 23 Oct 2012 02:32 PM
running the ERV for a little longer to get the moisture out is definitely preferable in nearly all cases to losing all recovery on what can easily be 20%-30% of your total recovery ventilation.

Amen that brother. It all starts with a ACCA Manual 'J' heat load.

Posted By BadgerBoilerMN on 23 Oct 2012 02:52 PM

Posted By NRT.Rob on 23 Oct 2012 02:32 PM
running the ERV for a little longer to get the moisture out is definitely preferable in nearly all cases to losing all recovery on what can easily be 20%-30% of your total recovery ventilation.

Amen that brother. It all starts with a ACCA Manual 'J' heat load.

Heating summary Structure 17327 BTUh Central vent 8695 Equipment load 26022 Sqft area 4809 Sensible cooling equipment load sizing Structure 21396 BTuh Central vent 5640 Equipment sensible load 28929 Right now there is a Climate Master Genesis Series Model GRV/GRH042AF that is specified but I'm concerned that this is not the right unit with the redundancy that we would like to have. On the issue of the ERV, is that sized by sqft? Let me know if you need more load information as I'm uncertain how to read the entire Manual J 8th edition. Cheers!

I'm surprised that a house that well insulated has a heating load of 17327BTU/hr @ +29F (the 99% outside design temp for Placerville: http://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/Outdoor_Design_Conditions_508.pdf ) Most of the load is probably windows (both heating & cooling), but that may already be broken out in the report (doesn't have to be, but usually is.)

This house could be both heated & cooled with cheap ductless mini-split(s) with a seasonal average COP comparable to better-class geothermal in that climate, with much lower system design risk, and dramatically lower up front cost (unless you insist on a head in every room, which some people insist on rather than doing the math.) The very open floor plan makes this even more attractive as an option. Going with high efficiency ductless and spending the difference in upfront cost on (heavily subsidized in CA) photovoltaics could very well be a better ROI than geo. with loads that low you can probably hit Net Zero Energy if you have reasonable roof orientation and shading factors.

With Placerville's dew point averages & climate there's next to nothing gained by going with ERV rather than HRV, and HRV would purge bath/cooking moisture somewhat quicker. Outdoor air there is not too humid in summer, not to dry in winter, mostly "just right", with dew points averaging in mid- 40s in summer, mid-30s in winter. (Pull up temperature & dew point graphs on Weatherspark.com and scale it to cover a full year with the slider at the bottom.)

Whoever started your project with geo created a terrific waste. See Dana1 above.

I am heating a 6,000 sf ICF home in a climate only a little warmer right now than your winters and I am running a single minisplit head to hold 68F. One ductless head keeps all three floors comfortable and it cycles on and off.

@ Rob,
The geo exchange loops are installed behind the 1st floor walls that were back filled. Then the 2nd floor concrete covers up this area. This is directly below the center of the entire structure. 2nd and 3rd floors are the same size.

@Dana1,
Using the placerville graphs doesn't seem like it's correct. The elevation of Pville is about 1800 feet vrs, we are are located deep in the canyon on the river that is at 975 feet above sea level. The weather is super different just about all days. Our property faces directly south and gets quite hotter in the summer and quite warmer in the winter than Pville. At this point in the build, installing ductless mini's is out of the question since we have radiant tubing already installed everywhere. I had meant to say that we wanted to use the HRV. I just got them confused but again, I don't know how to size that.
We only have 3 bathrooms.

With about 3F/1000' adiabatic cooling, your 99% design temp would be about 32F if you're ~1000' below Placerville. Since the sun doesn't shine at night, the fact that the average winter temps are more than 3F warmer than Placerville doesn't change the design temp much- give it another degree, two at most. The dew point information is nearly identical- it's the same air mass. Yes, it does get colder than that, but for only about 1% of the heating season hours.

It's not a big deal- being 3-5F warmer at night than Placerville lowers the design condition heat load numbers by roughly 10%, even if the much warmer days give you a much higher average, with many fewer heating degree-days.

Going with geo just to drive the radiant is still a waste- more money for equal or potentially lower efficiency. The fact that the tubing is in the floor means you can dedicate it to active solar hydronic that is completely separate from the rest rather than spending even MORE money to design & build an either/or system that takes it's heat input from multiple sources. You'd have to price out the relative costs, but the Daikin Altherma air-to-hydronic heat pump (using the same mini-split compressor technology) would also hit in the 4s for heating season COP, and would probably be cheaper than geo. (NRT.Rob can tell you all about it- he's heating his office with one where the design temp is in negative single-digits F.)

There are far fewer design risks to these systems than with geo, and it would SUCK to spend 2-3x the money only to end up with 75% of the efficiency, eh? Yes, geo can hit the 5s for annual COP, but only with world-class designers designing the system. The typical whole system geo efficiency (all pumping power accounted for) is in the mid-3s, mid-4s if it's a better than average design, and in your climate you're pretty much guaranteed to hit mid-3s and up with inverter-drive mini-splits, with very little design work required beyond the room-by-room/zone-by-zone Manual-J to size it right. With open floor plans, high-R, and decent windows one ductless head per floor usually works fine, if you place it right.

This house might do better with a heat pump water heater (HPWH) too, given the price of propane, and the significant cooling season. Heat pump water heaters pull heat from the house and pump it into the water, taking some of the cooling load off. During the heating season that heat has to be made up by the heating system, but if you're using a combination of passive & active solar and mini-splits it'll still be much cheaper than heating water with propane. The down side to HPWH is that the recovery times are slow, and some are pretty noisy (but they're getting better.) Only if you have some monster tub to fill would condensing propane be the better option.

At this point in the build, installing ductless mini's is out of the question since we have radiant tubing already installed everywhere.

You can use an air to water heat pump and still take advantage of the radiant tubing if you feel you need to.

I need to use the geoexchange since it is already in place.
It's easy but again, is my equipment sized correctly? Should I be looking in a different direction namely a boiler systemor a solar hot water tank with a 2nd line set to do the DHW?
Really that's the question......What is the best equipment to do the best job given the scenario?
I'm all ears!

Any thoughts or suggestions on the equipment?

1) Ductless mini splits will give you both heating and cooling for less than installing the geo equipment.
2) Installing a Daikin air-water heat pump will enable you to use the radiant tubing, and you might get some limited cooling from it.
3) Some solar might be feasible utilizing your radiant tubing.


An HRV doesn't require much sizing for most residential construction. 190 cfm works for all but the biggest mcmansions and most models can do about that.

B.b.b. but you don't get it, "I need to use the geoexchange since it is already in place." :-)

The Daikin would have condensation issues on the distribution plumbing if going for chilled-slab cooling at the 28K cooling load, or at even half that, but then so would the geo fan-coil approach.

Ductless heating/cooling + heat pump water heater makes the most sense and would come in under $10KUSD. Using the radiant strictly for hydronic solar or wood-boiler if desired makes more sense than plowing even more money into the geo approach just because the geoexchange is already in place.

My wife and I have horrible allergies and our thought was when we designed the house, we would not use any forced air.
So, if in fact I have to throw a bit more money at this for the right equipment to keep us from having moving air, I'd rather go that route. But, if it's not feasible, I'd like to know that.

Did I mention that the 3rd floor is 2437 square feet? The second floor is the same size as well so we're talking 4874 sqft.
After experiencing how this house performed during this summer (with many open holes, temp doors etc) the only cooling that would be needed would be on the 3rd floor. I'd bet the manual J cooling loads are wrong for this reason but we could use a ductless here. I just was under the impression I could pull the 58 degree temp from the ground with the geo for this floor. Honestly, I think we only have 10 or15 days a year that we need to cool.

With horrible allergies, I would concentrate on air sealing, pressurization, filtration and the materials used.

Minisplits are not so much forced air as they are moving air. Outside air should enter your home via the HRV. It has filters and you can add additional. Moreover, you should look at minisplit cassettes closely as a number of them have substantial filtration within which means your room air will get filtered over and over.

Even if you had radiant, you would have to have an air exchange system to move air.

Posted By jonr on 31 Oct 2012 03:47 PM
With horrible allergies, I would concentrate on air sealing, pressurization, filtration and the materials used.

We have done this as I know it will help in all of those areas. Where we live, it's dusty!

I anticipate the HRV will move enough air and exchange air that is needed for fresh air and dehumidification in the 3 baths and kitchen. The radiant should move with convection as I understand it and keep allergens down but still be able to heat efficiently.
I seem to feel you guys are hell bent on mini splits for my application but I really don't want them nor have I planned areas for fan coils to be located outside the envelope.

For the redundancy, I'm thinking of going with a Pheonix Evolution 80 gallon tank using propane and a climate master TMW 036 using the geoexchange. A reversing valve on this unit for a single cooling coil for a mini spit on the 3rd floor only. Wouldn't this work?
Again, I may be able to store some heat in the ground through the summer and pick it up for the winter as well on the geo side.

Additionally, if we ever offset this house with solar, the climate master could take over realistically. Right?

What about the bedrooms? That is where you need the fresh air supply.

With ICF you can easily hang the outdoor unit on a blank outside wall somewhere.