Been adding UnderFloor Heating to my own house and it's running provisionally. Controls yet to be wired. Can't think of ideal system but this is the best I can think of myself: Since the UFH is auxiliary to a radiator (theoretically not enough output from UFH to hold its own in cold weather), I decided to try plumbing the manifold (with pump, mixing valve assembly etc) with flow and returns from the heating circuit and room temperature control using the same stat that runs the central heating. Timber floors and spreader plates, so response time isn't too bad. Existing room stat is in the room heated by UFH - house is open plan and most of the heat goes upstairs anyway, but bedrooms do not overheat as they are controlled by TRVs and doors kept shut. Basically, the UFH will come on when everything else is on. The radiator will provide the main heat, and then the UFH will help keep the room and floor warm. In warmer weather, the radiator can be shut off using the manual control valve. I know it's usually advised to have the UFH on its own zone, but my thought is that all that will happen is that my old cast-iron-heat-exhanger-non-condensing boiler will cycle continually and reduce the system efficiency significantly (that would be an 8.5kW boiler running at 1.2kW demand... ) and heat losses from pipework would effectively heat the whole house to some degree anyway (centre terrace - so not a huge heat requirement) . The radiators in other rooms currently in use are just two - my bedroom (in practice, the TRV normally closes fully) and the bathroom (600Wish, but usually half-warm due to TRV). Also, days like today the windows can be open most of the day and it seems wrong to have heating on with open windows. Last three days heating has been on for an hour or two each evening and then I switch it off and sit by the fire instead. Does my reasoning about the UFH make sense to anyone else, given that I'll be the one using it? I know I'm weird, but I wanted a reality check when it came to system design.