yes 'flufster', that is exactly what i was trying do, i was wondering how economic you make the system and it seemed a waste of 'warm' water on the return from the rads. i have read a lot of the heave hoing over which boiler is best, but am considering the veissmann 200 w2bc, it the bunf it says it can run 2 mixed circuits one un mixed (ie 2 ufh zones and rads) and i assume the dhw, i was wondering if you were well informed about this particular boiler, if this then negates the need for all the same manifolds and motorised valves you would normally expect to see in a ufh system, as it is all controlled by the boiler? i was also considering laying ufh heating pipes on the out door terrace under slate tiles as a solar heater, as it is france doesn't get too cold in the winter and the garden is full south in a walled garden, to preheat water, but was wondering the value of any solar system on a combi boiler?