Hi Folks, I'm building a solar assisted house in CT and would like to hear suggestions for heating. The house is 2 story with a walkout basement. R19 walls, R30 sloped ceiling and R38 flat ceiling. Each floor is 720sf. The basement, currently unfinished has R10 insulation and 2 circuits of 1/2" pex about 280' each. The main floor and upper floor have Myson flat panel radiators sized for 16,000 btu at 140 degree water. The lines are 1/2" pex home run to a manifold for each floor. The goal was for the sun to heat the main level during the day, when the sun goes down close the window quilts and have the heat system kick on to keep the heat at about 64 degrees then setback the thermostat at night to about 60. When morning comes have the heat kick on for a couple of hours until the sun gets going. The main floor his pretty wide open and I have a small woodstove for those really cold days. The utility area is pretty tight being located under the basement stairs. I was planing on using propane with a direct vent option.  I would like to add a solar dhw to the mix in a few years. I received a quote  of $7200 for hooking up a mid efficiency  propane boiler. It seemed like alot for what I was getting and what I need.   Would a standard 50 gallon hot water heater or a demand hot water heater be able to meet both my heat and dhw needs today if it was setup with dhw priority and a heat exchanger for the space heating.  And.... if that makes any sense does anyone have any experience with the Navien heating box or their condencing demand water heater? Any help would be appreciated. Thanks Kurt      

Have you looked at even air to air heat pumps? It would be a lot less expensive then Propane, where are you located?

Hi Brock,  The house is located in Connecticut. I've already got the pex in the basement slab and the radiators are installed in the upper two floors so at this point I am locked into a hydronic system.  Thanks Kurt

You can still get an air to water heat pump, they work to about 10F and even at 35F outside are still pretty effecient, about 300%.

ModCon boiler with indirect fired water heater. You really can't afford anything else.

Hi Badger, Thanks for the reply.  Wouldn't something like a Bradford White Combi2 water heater work for my situation. It's not as efficient as a mod con, but I do plan on adding a solar preheat tank to the equation in a year or two.  With that setup wouldn't I get the benefit of the solar preheat for both domestic and space heating. Would the added cost of a modcon for heat and hot water (initial cost, annual service, service life} offset the costs associated with the Combi2  (lower efficiency, shorter service life). Any idea of what kind of service life you can expect from a combi2? Thanks for the help  Kurt    Happy 4th everyone

In your clime expect solar to pull 25% of your domestic hot water load. That's it. No heating, not even on a good day. I spec. quite a few CombiCor's but they are mostly for basement radiant and DHW combinations. For serious business (homes over 1500 sq.ft. generally) a ModCon with indirect makes sense: 20 year life span, regular maintenance (by-annual) and 25%+ fuel saving over a conventional boiler or water heaters such as the Combi-Cor.

To put it simply: the Combi-Cor will have a 300°F stack and the ModCon boiler around 100°F. This is real green man.

Aermec Heat Pump, air to water