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Venturing gently into the Boffins' Corner, I am after some help to try and come up with a heating / water / ventilation system for rentals which will: 1 - Not involve gas (trying to get rid of Annual Checks, and the plain worry of gas appliances going wrong). 2 - Will not slug the EPC figure. I am regulated to be D or better from 2025, and C from 2030, and not to comply will be a criminal offence - though there are exceptions. 3 - Will not be overtly expensive. 4 - WIll be essentially maintenance free, which ideally means minimal self-done maintenance once per year, and professional assistance once every 5 years. This will be a slow-burn, but as a starting case study, I want to work on the real world renovation of the Little Brown Bungalow. This has been easy to renovate so is a good example for a first try - and there another 49 identical properties in the street to do next time. I may get a copy of the Stoma data from my EPC an, but the project characteristics are: a - Floor area is 64sqm. 3 beds, reception, kitchen, bathroom. Suspended wodoen floor over a concrete raft foundation. b - EPC will be 76 or 77 in the C band. Previously was 47E. c - I have addressed all the low hanging fruit and a bit more. Underfloor insulation 100mm rockwool + 25mm PIR. 27mm loft inculation. Good double glazing. Modern boiler (Ideal Vogue) + rads. 50mm cavity wall insulation. Background ventilation is a PIV fan at the far end of the hall, one end and an HR Trickle Fan in the kitchen. d - Attention has been paid to airtightness and detailing. e - The obvious weakness is the 0.55-ish U-value of the walls. f - Realistically energy costs should be around £500 per year give or take, and demand could feasibly be under 10kWh per year - the previous EPC number was 13.4kWh predicted from the EPC. g - As a marker, the all new heating/water system and the ventilation kit added up to £4k installed. EWI would be prohibitive unless substantial grants are available - looking at 25-30 year payback on the £8-9k I was quoted. If I need to I can do more modelling; I think I probably need to do some proper thermal modelling eg the @JSHarris spreadsheet. If there was a way of using them effectively without complications, PV would be a good thought as it would also benefit the EPC (2.5hWp would put it up to nearly the A band). My initial questions: How close is this to being practical as a low cost electric only house? Does the thermal demand need to be mitigated further? How can that be done? Pump LECA or EPS beads into the subfloor, perhaps? What sort of technology mix would be suitable in this rental application? ASHP? Storage Heaters? Sunamp? Economy Seven? MHVR combined with warm air heating? What to do with any solar panel output? Are there any creative possibilities? If we can come up with a good ideas, I would be willing to try it out on another identical bungalow in future if one comes up for sale. Cheers Ferdinand

Has anyone experience or opinions of the type of Underfloor Heating which are put on top of a suspended wooden floor? eg This one from Polypipe says it sits in a 18mm depth, and a "housepack" for a 50 sqm heated area 5 zone area works out at about £2.5k. Though of course it needs insulation below and a floor base above. Are they: 1 - An excellent product. 2 - A good product but with compromises. 3 - The spawn of the devil. This is part of the gas free rental conversation, but I thought a separate thread was merited. For me, thoug this seems pricey, it may be a good way of getting rid of rads altogether, which can then potentially be connected to a wet ASHP. My need is to do it properly, and then more or less leave it alone for 15 years. Also, ufh does have kudos in the rental arena. Any views - especially @Nickfromwales. Cheers Ferdinand