roblane321

@JohnMo Thanks John - could you elaborate on your thinking a little for me? e.g. Is that purely down to losses through the floor? In case its relevant : From electrics standpoint the house and annex are currently on the same meter. I work from home full time in main house which has small 2KW PV array (21p FIT) that helps with usage through the summer as does Solar thermal. I wonder if we could get the two buildings on different meters? On the other hand we have room for more PV on the main house and have been considering adding separate system with battery so E7 would work better then if charging the battery overnight through the cold months? Sadly the annex is very heavily shaded so no PV option.

@Temp Finished floor will be 9mm laminate with stone / ceramic in the bathroom / hall. Multiple loops - I see the logic yes - thanks

Perhaps not quite the only question but it gets me started. Have been working on retro fit / converting an old single skin block outbuilding at home (cornwall) having been given PP to turn part of into an Annex. The time arrives to make a final decision about how to provide heating / dhw For context this is a single double bed, bathroom (shower only), entrance hall and kitchen diner for a total of about 50m2 (13 x 4) floor space. We've put on new roof with 100 between rafters and 50mm PIR. Wall insulated inside and out 50mm + 70mm PIR and then timber clad. Original floor slab has (only) 70mm pir on top currently leaving 65mm for further build up (50mm ? screed + 15mm finished floor). Doors, windows and roof lights all 3G. Yes it would no doubt have been better to knock the whole thing down and start again / especially to get more depth of insulation in the floor but that's not where I am now Expectation is permanent single occupancy - a genuine granny.. The plan had always been to go UFH and with my eco futures head on preferably with ASHP despite not being eligible for BUS but the quotes (12k for 5kW ASHP / UFH system to 25 K same inc all the DHW work) have me seriously wondering if I should consider alternatives or just get on with it... We've no mains gas and I'm not interested in oil (main house is oil and at some point we'll try to change from that to get BUS). so what does that leave? Bottled gas with combi boiler for all DHW and UFH? Bottled gas with combi boiler for all DHW and Rads substitute screed for other 40+mm floor PIR for floor? All electric (No UFH except in bathroom substitute screed for other 40+mm floor PIR for floor Stick with ASHP UFH but do as much as I can myself and just get in whatever necessary external skills (Not entirely sure what that would really mean). Stick with ASHP but switch to rads and add another 40mm PIR to floor Ignoring the upfront cost I assume ASHP is the most cost effective from a run state expenditure (~1300 v's ~3K for all electric @ 26p\kwh?) From reading on here for the UFH design seems like it would probably best just to go for a single zone? Any comments / thoughts / alternatives..about things to avoid from design perspective? (and so leading to requesting spec changes in h/w) Ta Heating.pdf