resumably already committed to buying. If you're already going for a woood= stove(?) fired thermal store, then this solar extra makes sense. (ALthough = the external heat exchanger approach is a good one too.)
lar capital costs are 50% to achieve space heating, 50% (or more) to add on hot water and a thermal = store. So unless you're opening a Spanish laundry, solar heating is (IMHO) = a great way to space-heat in UK autumn and spring, but an over-expensive wa= y to heat your hot water.
eated floor system for that.
I sort of see the two components here as different: On the one hand, the t= hermal store (driven from=20 the gas boiler) will provide advantages in configuring the DHW for the hous= e (a 6-bed Victorian on 3=20 storeys) as it will give mains pressure HW through an external heat exchang= er without the issues=20 associated with unvented cylinders. From an economic point of view, that= =92s already going to be =91paid=20 for=92 under that agenda (including allowing an en suite to be installed on= the top floor), so anything else=20 I do with it is at marginal cost. On the other hand (time and enthusiasm permitting), it may provide the flex= ibility to go a bit green by=20 playing with the solar side, which appealed to the experimenter in me rathe= r than thinking of it as=20 necessarily cost effective per se (which it would probably never be if I bo= ught a ready made solar=20 system), but the cost wouldn=92t be great if I DIY, which would allow me to= customise the design to=20 exploit the site. Now, as part of other works, over the next year or two I shall be laying a = couple of new floor slabs=20 (conservatory refurb, kitchen extension) =96 in all about 50m2 and (to me a= t least) it makes sense to=20 incorporate UFH into these whilst laying them anyway. Given the different temperature requirements of the UFH, it may be sensible= to consider driving this=20 from the thermal store rather than directly from the boiler. If there was = a significant solar=20 contribution, this would then be exploited by the UHF. If that works out (= as you indicate it=20 might), so much the better, but my initial thinking was that the solar yiel= d wouldn=92t be enough to make=20 a serious impact here. I could, of course, easily be wrong. In a way it d= oesn=92t matter: If solar helps,=20 then fine, if not, I=92m back where I started, running it all from the boil= er. Wood burning isn=92t really on=20 the agenda at present but who knows?=20 At present this is all in the planning stage, and I haven=92t committed to = anything. In the spirit of=20 =91measure twice, cut once=92, I like to think through all the connotations= of future plans while I=92m doing=20 the current jobs (finish living room, refurb d/stairs bog etc) so I have th= e details worked out before I start and avoid stupid/expensive/time consumi= ng mistakes, especially with a whole range of projects=20 to be implemented over the next few years. Of course, this group is invaluable in refining such plans, which have deve= loped pretty significantly=20 from my initial musings in just the few hours since I first posted (!)