When I was stationed in Hawaii, I lived in military housing. They had the AC heat exchanger and the water heater tied in together somehow. The heat from the AC somehow helped heat the water in the water heater or it was hooked up directly. Like supply line in to the AC heat exchange and then to the water and out to the rest of the house for usage.

What I would like to know is there some company that does this and their web site. I planning to build a house and want to make it as green as possible.

From my understanding talking with the plumbers this system is very cost effect and saved a lot.

Where will you build the new house? Some high end furnaces have some sophisticated heat exchangers with their exhaust gases. If you want to save money and fuel with your hot water you might start reading about tankless water heaters or point of use heaters. Rheem Tankless Water Heaters (http://www.rheemtankless.com/content/)

When I was stationed in Hawaii, I lived in military housing. They had the AC heat exchanger and the water heater tied in together somehow. The heat from the AC somehow helped heat the water in the water heater or it was hooked up directly. Like supply line in to the AC heat exchange and then to the water and out to the rest of the house for usage.

What I would like to know is there some company that does this and their web site. I planning to build a house and want to make it as green as possible.

From my understanding talking with the plumbers this system is very cost effect and saved a lot.
I'm planning to build in the area of Iowa City, Iowa. I was under the impression that tankless water heaters were not cost effective to use. Since it takes a lot of power to heat the water when using.

Not so, they use less fuel since they only turn on when there is a demand. If you use not hot water all day you still heater 40+ gallons to 120 all day. A tankless would use zero fuel in this situation. A lot depends on your usage. They come in natural gas, propane and electric running anywhere from $700 on up. I just got an extra $300 from Uncle Sam for an energy credit on the purchase. Not enough sun in Iowa to talk about solar but some folks use insulated solar panels to preheat the 50 degree water coming in from your supply.