I'm looking at building a highly insulated new build with several heat sources and several different heating requirements. I'm concerned that what I'm trying to do may be too complicated to effectively implement, or there may be a better way to do things, and I'm looking for feedback.

Heat sources:
Solar thermal
Back up boiler (either mains gas or GSHP)
Wood stove (no back boiler)
Drainwater recovery

Heat sinks:
Underfloor heating
Domestic hot water
Towel rails in bathrooms
Small indoor swimming pool (http://www.endlesspools.co.uk/index.html or equivalent)

I'm thinking of using a large cylinder, with heating coils from the solar and backup boiler, storing the water at a fairly high temperature which I think is fairly normal. (2 coils so far.)

The stove is really for decorative use and the one we're looking at doesn't provide the option of a back boiler. It won't be on all the time but will kick out a fair amount of heat once it's going.

Underfloor heating would be taken from a coil inside the tank and mixed with return water to stop it getting too hot. Again, I think fairly normal. (3 coils so far.)

In theory I think the towel rails could be heated from a separate coil, or from the same coil as the UFH with a mixer set to a different temperature. I hope that the latter is possible to simplify the system. (3 coils so far.)

I'd like the DHW to be supplied from a feed-through coil in the thermal store so that it is still mains pressure. I don't think this is very unusual either. (4 coils so far.)

The pool will be small (about 9m3), indoors, well insulated and will be heated to around 28C. Normally this is done through it's own gas or electric heater, but I'd prefer to tap it into the whole house system to take advantage of solar,
at least in the summer. I'm hoping that this could also be heated from the UFH/towel-rail coil using a heat exchanger. The large thermal mass of the water should mean that this can be lower priority to other heat sinks, and could be controlled to stop heating the pool when it has drained too much heat from the thermal store, even if this means the pool isn't at target temperature. (Still 4 coils so far.)

The final complication is that I'm considering the use of drainwater heat recovery (we mostly take showers) with a system like that offered by http://www.shower-save.com/. The mains cold water goes in one end and the pre-warmed water from this would directly feed the cold tap for the shower and the DHW input to the thermal store. In principle this seems fairly simple, and doesn't complicate the thermal store.

Does this sound like a good way of setting the system up?

Is it going to be difficult to balance all the sources/sinks so that we have something comfortable?

Is there a better way of doing it?

Thanks very much,
Mark.

Were it not for your pool I'd completely agree with Tony, no need for anything other than a woodburner for a well planned new build. But you'll need to heat your pool. Makes sense to integrate pool heating with solar/ UFH / towel rails in that instance. Pool water needs to be heated via a heat exchanger. You've got a coil problem. Go for a vented thermal store instead. You'll need to ensure that the pool doesn't overheat the house in the summer.