I am building a ICF house about 4500 sq ft this consists of 2300 sq ft living space with a 2200 sq ft unfinished basement (we plan to finish most of basement and use in the future). The house is located in KY our summers are hot and humid winters can get pretty cold too. I already have pex in slab for radiant heat. Now I need advice on the rest of the heating and air. I only have access to electricity and will be putting a 500 gallon Proprane tank at site too. Thanks in advance for any helpful advice. Wayne

Every good heating solution begins with a heat load calculation. The fact that you have ICF walls means that you have somewhat better-than-code walls, but it doesn't tell you what the heating & cooling loads are going to be. The U-factors and total area of the windows, the air tightness of the house, the R-values of the attic are all large factors in a heat load calculation.

Windows, particularly WEST facing window area can dominate the cooling load numbers. Putting ducts & air handlers in the attic instead of conditioned space can add a lot too, and with that many potential leak points in the ceiling, often drives air leakage rates way up (both winter & summer.)

Hopefully you put at least R10 foam under the slab, and the loops of PEX don't exceed 300' in length(?).

If you do the rest of the place to code-min, using a crummy rule of thumb approach your heat load is going to be something like 10 BTU per square foot of fully conditioned above-grade living space or about 23,000 BTU/hr, but it could vary from that by quite a bit (in either direction) based on the particulars. Whatever it turns out to be, it's probably lower than the output of almost all propane boilers and propane hot air furnaces, but it IS within the range of air source heat pumps, which would be much cheaper to run than a propane-burner anyway. The heat load of a 2200' ICF basement with an insulated slab is going to be under 10,000 BTU/hr, probably even under 5000 BTU/hr , unless it's a walk-out with a lot of sliding glass door or something. A hydronic loop off any tank-type hot water heater (with an isolating heat exchanger) would be sufficient for running the radiant floor.

Using a similarly crummy & faulty rule of thumb, the cooling load of the 2300' upstairs is going to come in at 2-2.5 tons, unless you put the ducts & air handler in the attic above the insulation and outside the pressure boundary of the house, which adds at least a ton. But with a lot of west-facing glass it could add another ton of cooling.

Bottom line, getting to the right solution that delivers the best comfort requires an actual heat load calculation. Better yet, model the thing using a pretty good freebie tool such as BeOpt, which will allow you to play "what if..." games with the specifics of window types & R-values etc. as you go.

If it isn't already too late, using an extra tall "energy heel truss" for the roof or a double-chorded truss would allow you to put the IRC 2012 code-min R49 in the attic, and still have sufficient room for a service chase below the insulation to accommodate ducts & air handlers, power & plumbing etc above the finish ceiling. Otherwise, it's often possible to bring the air handler & ducts inside the pressure & thermal boundary of the house with interior soffits, etc. In a house with a basement, putting that all in the basement makes the most sense, even though the AC guys all seem to think hot attics are the perfect location for the cooling mechanicals.

In KY (US climate zone 4A), it's possible to build a fairly high-performance house if starting with an ICF shell.  See the row for zone 4 in Table 2 p.10 of this document. Note, all R-value are "whole-assembly" values, after factoring in the thermal bridging of any roof/truss framing, etc.   Starting with a 2.5" + 2.5" EPS ICF you're already at about R22, ~10% shy of their recommended R25, but an ICF has sufficient dynamic thermal benefits from the thermal mass of the concrete to more than compensate. And you're already above the R20 recommendation for basement walls.  If you use the other values for roof, slab, windows, etc, you'll be in VERY good shape from a heat load point of view. But what that heat load is still has to be calculated to get it right.  Oversizing the heating/cooling equipment takes a toll on comfort, efficiency and equipment longevity, so it's worth running the numbers rather than relying on dumb rules of thumb and upsizing "just to be sure".

Thanks for the response. I plan on using heat pump with propane back up heat. Also the radiant heat loops are all equal length and if I remember correct about 250-280 feet but for sure less than 300. I did insulate under slab as well. I used Nudura ICF forms from ground to roof line. So far I have done all the work myself with help when necessary. I plan to have all duct work in the open web floor trusses. I have no west facing windows due to garage being on that side of house. Again thanks for all the information.

With 2 ton variable speed compressor & air handler would almost certainly handle the entire heating & cooling load of the above-grade floor. Play around with the different compressor & air handler combinations after pressing the "Heating Capacities" tab on this page:

http://www.tools.carrier.com/greenspeed/

The 99% outside design temperatures in KY run about +10F to +15F, a range at which the 2-ton Greenspeed can still deliver north of 20,000 BTU/hr. With a tight build you probably won't be over that. Assuming a 15% window/floor ratio, that's 345 square feet of window, and even with code-max U0.35 windows the window losses at 70F indoors, 10F outdoors the window losses are only about 7250 BTU/hr, throw in a couple of doors and call it 7500 BTU/hr. The wall losses are probably less than 5K, a 2300'/ R49 attic combined would add up to another 7500 BTU hr and you're up to 20,000 BTU/hr- the rest is air infiltration/ventilation, which can be throttled back during the coldest weather in a tight house if need be. If you want more margin, a modulating 3-tonner isn't an efficiency & comfort disaster, but hold the line there. If going with a simple single-stage unit you may actually need a 3 ton unit to be covered at 15F or lower outdoor temps, and it'll use more power than the modulating units on average.

If it's a fairly open floor plan you can probably cover the entire load with a couple of high-efficiency mini-splits at high efficiency, for less money than a modulating ducted heat pump system. A 1-ton Fujitsu RLS2 or Mitsubishi -FH delivers more than 13,000 BTU/hr @ +10F, but it's sort of like having a wood stove- it heats the room it's in directly, but you need open doors or an open floor plan to distribute that heat into the other rooms. (And higher performance windows in the doored off rooms may be necessary to limit temperature differences.)

http://usa.mylinkdrive.com/uploads/documents/4561/document/MSZ-FH12NA_MUZ-FH12NA_Submittal.pdf

Roy, What part of KY are you building in?

Whitesville Ky which is just outside Owensboro.

Also forgot to mention this is a walkout basement. About 70 feet of basement wall is open(not backfilled against).

This may seem like a dumb question but a guy that is planning to help with trim work mentioned adding a humidifier b/c with gas heat it will dry things out. He likes to do a lot of fancy crown etc... and is afraid wood will dry out causing cracking and caulking to crack leaving his detailed work looking like crap. Based on everything I have read usually with ICF house people are trying to get rid of humidity issues if anything. Any thoughts on this would be greatly appreciated.

Roy, I am originally from Ohio County, about halfway between Owensboro and Bowling Green, KY. With the current weather, I am happy to be in Alabama.

I am actually with in minutes of the ohio county line. I wish I was somewhere warmer for sure. Tonight they say we will be -10 with real feel around -25. Too cold. I wish our new ICF house was finished we would be more comfortable lol. I see you have made a lot of posts. Do you have a ICF house or are you in the business?

Roy, In 2004, I retired from teaching in the School of Architecture at Auburn University. For several years I have specialized in design and construction of homes with materials other than wood such as Insulated Concrete Forms, Structural Insulated Panels, Structural Concrete Insulated Panels, etc.

In new, tight, construction a humidifier would not likely be needed.

Forced air is a factor in older construction often increasing fenestration and consequently heat loads, humidity, etc. But you will have an ERV for IAQ and worry more about too much humidity rather than too little until summer...

Posted By Roy Castlen on 18 Feb 2015 09:43 AM
This may seem like a dumb question but a guy that is planning to help with trim work mentioned adding a humidifier b/c with gas heat it will dry things out. He likes to do a lot of fancy crown etc... and is afraid wood will dry out causing cracking and caulking to crack leaving his detailed work looking like crap. Based on everything I have read usually with ICF house people are trying to get rid of humidity issues if anything. Any thoughts on this would be greatly appreciated.

That concern is ridiculous for any reasonably tight house, and way off base for a brand new ICF house.

Heating systems do not add or remove moisture from the air- ventilation & infiltration do.  It doesn't matter if you're heating with gas, a wood stove or a heat pump- if you build the house to IRC 2012 levels of tightness (< 3 ACH/50) you will have no problem controlling the humidity levels by how much you run the ventilation. In fact, in new construction there is a lot of residual humidity in the wood & concrete, and the first year or so you'll usually have to either ventilate at high rates or run mechanical dehumidifiers (or both) to keep the humidity levels in the 35-40% range in winter.    If you go much higher than 40% you're more likely to run into copius window condensation issues or mold-growth on the cool side of some of the building assemblies that are made of wood. 

In general humidifiers are a solution-problem-  they increase wintertime comfort levels in air-leaky buildings, but they also create moisture problems in the same buildings.  If you build tight you will not have the dry-air comfort problems unless you actively over-ventilate the place. It's good to monitor the humidity levels anyway, even if it's just a few cheap battery operated Acu-Rites.  Anything between 30-50% RH is healthy & comfortable for humans, but in winter it's better for the house if you stay closer to 30% than 50%.  In summer in your climate you will have to run air conditioning or dehumidifiers to keep it down to 50%.  While 60% is still OK from a comfort point of view and is still fine for the house (when it's warm out), anything over 50% allows dust-mite populations to thrive.