I am planning out a ICF house and can't decide what the best water heater is.  I am planning on putting a geo thermal heatpump in and was originally planning on heating the water via this but now am worried that due super insulation qualities of ICF the heatpump won't run enough.   I won't have gas at the new place so I am now thinking a solar hotwater heater might be better. 

regardless of how you pre-heat your water I would use a whole house tankless water heater. Even though gas operated ones perform better, the electric ones are good too.

Chargerag,

I'm a little curious on the size of home you are looking to build. I may be ridiculed by some (wouldn't be the first time), but if you are looking to build with ICF does it make much economic sense to install a geo thermal heatpump too? Most of the architects and engineers I have worked with do not think so unless you are building a really large home. I would instead invest the money in an energy efficient heat pump and energy efficient windows, especially if your house can take advantage of passive solar.

With regards to the water heater, I just switched mine out and I seriously looked at the electric tankless heaters. They require 220 v (I didn't want to do all the rewiring) and I have heard that they are not as dependable or as efficient as gas, so I stayed away from it. I think it would come down to a personal choice and it would depend a little on how much you look to use hot water...do you have a family of 4 or 2? Depending on how much you will require the use of hot water, the cost differences between systems could be marginal. Why can't you have a propane tank installed outside the house?

renangle

I completely agree with the first paragraph.  Unless it is a VERY large home or money is no object, doing ICF and geothermal is overkill.  Don't get me wrong it would be a great setup, but the payback on the geo investment would be decades in my humble opinion.  I was looking at doing that very thing, but I will instead be getting good windows and as efficient a heat pump as I can get.

With regard to water heaters, if you are going tankless I would avoid the electric like the plaugue.  They are energy hogs.  I would go gas, but my first choice would be something like a marathon water heater.  They are very energy efficient (5 days after losing power you still have 100 degree water) and they offer a 45 year "bumper to bumper" warranty.  They are electric but VERY energy efficient and no rods inside either.  Again in my opinion, they are youre best option besides tankless gas, and in some ways better than.

But I'm sure others will have another opinion.  Fell free to PM me with any questions of if you would like more info, I'll do what I can to help.

Hi,

I am from Europe and here we have a lot of brick and mortar houses. Cost of heating water is quite small and not so important compared to cost of heating. (Even with higher energy costs here.)

General rule is, if you have heating pump, use it for water too. Any HP will have no trouble providing you with hot water.

When saying geothermal heat pump, do you meand ground sourced (e.g. 2 feet deep cable in the ground, using sun energy stored in the ground ) or you mean 100 feet deep vertical mine, using geothermal energy.

In Europe we have a lot of ground-source heat pump and they are efficient also for better insulated homes (read: ICF). The cost of heat pumps decrease with size, so better insulation commands lower installement price.

The key point to determine wheather to use air sourced or ground sourced heat pump are winter temperatures. Bellow around 0 degrees Celsius, air sourced heat pumps are not efficient.

Efficieny of (any) heat pump depends on heating temperature, so HP works much better with ground radiant heating.

At current energy prices (even European) it is difficult to make 100 feet deep vertical mine type of HP economically viable.

This is from WikiPedia:

"A [b]geothermal heat pump[/b] (also called [b]GeoExchange, earth-coupled, ground source or water-source heat pump[/b] ^[1]) system is a heating and/or cooling system that uses the earth´s ability to store heat in the shallow ground or water thermal masses.

Geothermal heat pumps are known also as "GeoExchange" systems because is a term created by an industry association^[2] and "ground source heat pumps", to clearly distinguish the technology from air source heat pumps. It is important to understand that ground source heat pumps draws energy from shallow ground. The energy originates from the sun: none of the energy originates from the centre of the Earth, in spite of the name "geothermal heat pump". Genuine geothermal energy from the centre of Earth is available only in places where volcanic activity comes close to the surface."

just because there is big difference in price and not so big difference in efficiency... :)

cost of ground sourced HP in Europe is about 1-2K bigger than air sourced HP

chargerag, where are you located? heating zone - cooling zone???

Chargerag,
I moved in to my ICF house in June, 08. I also have a geo in the basement. I agree with your concerns with the unit not running enough to keep the water hot. It would probably be fine in summer and winter, but in spring and fall here in Kentucky it doesn't run that often. Some days not at all.
My HVAC installer advised me to install two electric water heaters in series. The first one is not powered, but the geo circulates to preheat the water before it goes to the powerd tank. This way, you only heat the water 20-30 degrees instead of 80. Also you have twice the volume so you won't run out.

Renangle has a good point about the payback, but don't forget to take into account the install savings when you buy a lot smaller unit for the ICF house. A couple of other advantages of geo are:
1. The is no condenser outside to make noise while you're trying to enjoy that new patio. It's a package unit thts only a little louder than a refrigerator running.
2. I saw over on the geo furum the other day that there is a $2000 tax credit (not deduction) for installing a new geo. It's part of one of the stimulus packages. Fortunately for me it's retroactive to the first of 2008.

http://www.greenbuildingtalk.com/Forums/tabid/53/forumid/
13/postid/43413/view/topic/Default.aspx 

Witch ever way you go I hope you enjoy the comfort and security of you ICF house.

Greg

Chargerag,

I faced the same question when I started my 2000 SF ICF house project. I was planning on going with a georsource heat pump but my heating and cooling load calculated so low I couldn't justify the cost. I finally settled on, and installed, a Daikin air to air heat pump for my primary heating/cooling system and an AirTap heat pump for DHW. The benefits I get are; a) the Daikin puts out heat with a COP of 3 down to 10F, and, b) the AirTap heats water year round at a COP of 2.4 or better. The Daikin will put out heat down to 0F or colder but I don't know what the tested COP is. My unit was keeping my house heated in December when the outdoor temps dropped down to about 3 to 5F. The water heater is in the garage which is heated by a Daikin wall unit. In the winter the Daikin brings heat from outside into the garage with a COP of 3 or better. The AirTap then injects that heat into the water for domestic use. In the summer, when I want to cool the garage, the AirTap extracts some of that heat and puts it into the DHW thus helping to cool the garage.

Search for Daikin and AirTap in my past posts in this ICF forum, the radiant heating forum, and geothermal forums and you'll find more complete explanations of why I chose those units. My experience in the past few weeks has confirmed that I made a good choice.

I just glanced again at Greg's post above. Regarding noise, the outdoor unit of my Daikin system is next to my patio. It's noisiest in the winter when the fans run full speed in heating mode. You can easily carry on a conversation on the patio at normal voice level while the unit is running. It's unbelievably quiet!

Dmaceld, my father also has Daikin air sourced HP and has installed energy meters to measure COP. When temperature goes bellow 32F, COP goes to toilett. At 0F, COP is more or less 1.

In North America, everyone talks about tankless water heaters as the best solution - in Europe, it's solar-heated water with a large, superinsulated tank...

Two questions. Which model of outdoor unit is your father's? How is he measuring performance? It's a straightforward matter to measure power in, but how does he measure the heat output?

I really do want to know because I would like to be able to objectively assess my system's performance. If it's not as good as stated by Daikin I may not buy another one, and my HVAC contractor nephew may not want to sell them.

Dmaceld,

in order to objectively asses any HP, you have to take a look at meteorological data.

In case of my father, he can compare daily/weekly/monthly consumption of electricity (spent by HP) and compare it to consumption of heating oil in the past. It is not 100% accurate, but it is valid indicator.

We live in small country where on distance of 100 miles you get completely different climate. Therefore I can attest, how different HP perform in different circumstances.

In warm climate, air sourced HP perform great. And Daikin are great heat pumps.

For my father, ground sourced HP would be best, but he did not want to dig out garden. He opted for Daikin Minichiller.

Theory says: if the source temperature is 32F, if you are heating to 131F (no flour heating!), than theoretical COP is 3. (That is valid for all manufacturers.)

The magic question is, how many days do you have with temperatures bellow 32F? If few, your HP will have electric heaters installed, and electricity spent by these electric heaters is small.

If there are many days bellow 32F, you should look at ground sourced HP.

Or do like my father. He bought undersized, cheap HP to be used majority of the year, and oil burner to be used in peak winter.