We are building a ICF home that is 2649 sq.ft. on the main level with a daylight basement for a total of 5298 sq. ft. (3800 sq. ft. approx. conditioned).  Is it necessary, as we are being instructed, to put in 2 heat pumps to "balance" the HVAC.  It seems like it would be overkill and erase the energy effeciency we wanted in building with ICF's.  The basement is below grade on 2 1/2 sides with only 3 single windows and one door.  5 ton total has been suggested but it seems too much.  I am planning to use hvac calc when I settle the issue of 1 or 2 systems.  Any thoughts would be greatly appreciated.

Well, believe it or not, we don't have blueprints for this house so I don't have them to send to energywise. we took a plan layout and let amvic modify for the walls and what we simply did was to add the dimensions of the block to the outside footprint and adjusted the windows and doors accordingly. Has worked out beautifully. This is the third OB we have done. We have ran into zero problems, just a LOT of work and research.

Actually, I would think that the drawings done by Amvic, and a few other pieces of information should be enough to get a decent HVAC calculation. And I agree that one unit should be be more than adequate for your home.

I ran the HVACcalc 4.0 and got an answer of 2 1/2 tons but am a little leary of the small size. I will check with EWS and see if they can work with what I have. Thanks.

I am building a similar ICF home in west central Arkansas, but somewhat smaller. 8" and 6" ICF walls from footings to roof. ~R49 blown cellulose in attic. Brick exterior. Lots of shade in summer and no glass on west side. Main floor 2100 sq ft, with 1650 sq ft H&C in the walkout basement. Back of house and walkout basement face due south. I have more glass in the basement, 2 x 3'x5' windows plus 1 x 3'x6' window plus one 6' wide glass patio door.

I used the HVAC sizing software for ICF homes and came up with just a little over 2 tons load. I am planning on installing a single 3 ton dual speed geothermal heat pump system. I will have the system zoned separately for the main floor and basement. The unit will be located in the basement mechanical room. I am having open web floor trusses installed between the floors. This will contain my HVAC duct work for the main floor. I intend to use the entire open area between the floors as the plenum for the air distribution to the basement. The zoning for the basement will just consist of one large motorized damper on the main supply plenum dumping conditioned air into the space between the floors along with a motorized return damper in the basement near floor level.

Another thing I am installing is an air circulation fan of ~600 cfm that will take a suction at the peak of my main floor vaulted ceiling in the winter and at floor level in the summer and discharge into the basement air plenum between the floors. I plan to control this fan with a thermostat in the basement.

I am also keeping my options open for installing a dehumidifier or small mini-split heat pump in the basement in the future if needed (floor drains installed for condensate and wall penetrations where needed for HVAC lines).

You have a lot of good ideas. I wish we had open floor trusses. It sounds like yours will work fine. We are also supplying the main floor ducts in the space between floor joists. I like the idea of splitting the floors with a damper. I am trying to see if we can do that also. I appreciate the extra ideas. Good luck.

By the way, this is the HVAC sizing software that I used to size my system:

HVAC Sizing for Concrete Homes


You might want to run a load calc using this software and compare it to what you got using the other program. 

I think this may be the ideal situation for some mini split heat pumps. Ay of the major brands would work well mitsubishi, daikin, fujitsu, etc. You'd be amazed at how much you can downsize your system and with the new invertor technology, these systems are VERY energy efficient. In my humble opinion, this type of system is the perfect marriage with an ICF home.

I recently had our hvac guy give me the tonage for a 2500 square foot icf house and his j calc was 1.7 ton. Yes thats no typo. You could get a 3 ton system, have more than enough with 2 ton LESS that a traditional hvac system, NO ductwork, and a more energy efficient system. Now they have more sttractive cosmetic registers than the wall mount so it's easier for some people to use. Plus the installation usually takes less than 1 day.

http://www.daikin.com/global_ac/products/residential/index.html

http://www.mrslim.com/Products/Category.asp?ProductCategoryID=24

are to examples. I'm not associated with either of them. There is a reason that the rest of the wordl uses these systems and have for decades.

While Mini's are great for "spot" air conditioning , I would never recommend for a total home HVAC system in the US, they cost more, don't have good air distribution and look too unconventional affecting re-sale

While Mini's are great for "spot" air conditioning , I would never recommend for a total home HVAC system in the US, they cost more, don't have good air distribution and look too unconventional affecting re-sale



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You are incorrect on ALL counts. They do not cost more, they usually cost LESS. Even if the product costs exactly the same per ton, there is no ductwork to purchase and install thus saving the product and labor cost AND they are usually 30-40% more efficient to operate. Also, if you look at the links I posted, you will see that the traditional euro style wall mount systme is only one option. They now have "wall cassettes" that look just like a regular "American" register so the cosmetics is not an issue. 95% of AC untis sold in Asia are mini splits and 60% in Europe and Canada are and they have been in use for decades. They work great, last just as long as our traditional hvacs, cost less to run, CAN cost less to buy (at least not anymore), easier to install, and cosmetic is not an issue any longer. They also offer the homeowner the option of having each room be it's own zone. Since each register or unit in the house is essentially it's own zone, I can set it to freezing and my wife can set it to "florida" and we can be 1 room apart. Figure in the cost of that kind of zoning with a traditional hvac and the cost just skyrocketed IF it can even be done. Mini splits are the ICF's of the hvac world, the problem is that we are just now figuring this out.

Because of the energy efficiency of ICF construction this may not always be achievable. The smallest capacity indoor wall unit could very well be greater than the heating/cooling load of a small room. The economics become questionable if you need a bunch of small capacity units vs. fewer larger units. There are some ducted indoor units that can be installed to serve more than one room.

When I did my house I ended up using a single 36,000 Btuh indoor unit because I couldn't match smaller unit sizes to the heating/cooling loads of various groups of rooms. I installed the Daikin VRV-S 3 ton system.

dc your reply didn't show up. :)

Damn forum msg editing s/w. Jack around with the quote box and text doesn't stick unless you type it in on the tab page and try to throw in a smiley face.

So far it has been working great. One thing I'm impressed by is how it extracts heat (in AC mode) only as fast as it's building up in the house. The other evening the condenser fans were turning pretty slow and the air coming off the coils was barely warm. The outdoor temp was about the same as the indoor temp so heat was building up slow in the house.

I'm not sure about overall system efficiency. My power bill is higher than I expected so I'm considering installing a WELserver temp and power monitoring system. I expect I'll find I'm using a lot of energy heating DHW, a lot more than I thought I would.

Humidity is an issue only sometimes here in SW Idaho - it gets almost too dry!

I used a 9000 Btuh wall indoor unit in the garage. In the house I used a 3 ton ceiling duct mounted air handler installed in the crawl space. I have short duct runs going three directions to help direct the air flow, but basically the air is just dumped into the crawl space. I use the crawl space for the supply plenum.

Haven't relied on the Daikin through a winter season yet. Last winter while we were still building I used a temporary electric furnace and then the pellet stove for heat most of the time. Ran the Daikin some early in the spring and then all the time after we moved in in April.

DHW = domestic hot water

So far in AC mode the system cycles one time per day. The indoor unit fan runs constantly. The outdoor unit generally kicks on about mid day and stays running until late in the evening. Since it's a variable speed compressor and fan it runs only as fast as necessary to extract the heat from the house.

thanks! good feedback.