Okeb

Good to see we got to the same calculation (3400kWh vs 3432kWh). £270 a year yes, but with the radiator it is around £106-140 a year, so the difference is lets say £150, but better comfort I assume, so might still worth it. The white bits in the image are the insulation I guess, it's broken in pieces, but visible on some part of the floor closer to the wall, also closer to the bottom of the picture, pieces fall into the void also. I upload the full image, what shows a bit more. Unfortunately no access to the void, and you are right, the air bricks are likely vents for the void (as per this video: https://youtu.be/nuqlgDe33Gc?si=wfu0XLxeBOkZR0rq&t=22 ) Adding insulation to the floor, lets forget that it adds height, but a 100mm PIR would reduce heat loss by about £140 per year, but material cost is £1200 plus put it down, so it would take like at least 10-15 years to break even. And the vacuum insulation panels cost is just out of question. Will look into low temp heating with rads and consider my options, even boiler change or other improvements, but I am not fully disqualifying the UFH. Roof already has 200mm+ insulation.

You are right, image is cropped, but on the full one I referenced to a wall socket size and the total floor thickness is around 200mm But the void is air, and air is good insulator? It is under the floor with no visible air opening, unless brick air vents provide that, what I do not know. Thanks Gus, that is what I found, 0.25 W/m^2K So a bit of calculation, if I understand it. -100m^2 ground floor with the above U value -lets assume when heating needed it is average 4 degrees outside, room set to 21 degrees -Heating period of the year lets say 220 days 1, Radiators Thermostat at 21deg, close to floor is around 19 deg. Heat loss per year: 100 * 0.25 * (19-4) * 24 * 220 / 1000 = 1980 kWh 2, Underfloor I assume higher heat loss because we do heat close to the floor, what is warmer as well than the room Thermostat at 21 deg, what can be the temperature used? Maybe 30? (not directly the water temperature I assume) Heat loss: 100 * 0.25 * (30-4) *24 *220 / 1000 = 3432 kWh The difference is 1452 kWh, what is for a 8p/kWh rate on gas with efficiency of ~90% would cost £129. Is this how it is calculated? So I will be worse by £129 each year, but on the contrary comfort can be better, and maybe run at lower temp so it might be slightly lower?

Is there a way to know construction? Do they drill and check? The house ground floor is level with the ground. the only ventilation I could see to the void below the beams are the vent bricks. But I am not sure they are connected to the void below. So if the void below the floor is not open void, then it is a on it's own insulating as a trapped air, isn't it?

Thanks for your advise. The boiler is mentioned above. It has a manual knob to set the temperature, so don't think it can be connected to opentherm. https://www.mainheating.co.uk/main-products/gas-boilers/main-eco-compact-heat In one of the room downstairs I removed the carpet and the underlay, and checked with a thermal camera after a colder night (maybe 6-8deg), and in general the floor temperature was similar to the walls and did not see cold spots, only a small bit around the window. Room did not feel cold. That is is why I think it is "well" insulated, but I do understand that I can drain money to heat the void.

Hi, I read the forum extensively, and see that the general suggestion is not to have many zones (if at all), however there are many here also with off the shelf designs with multiple zones and they are also happy with it. In addition, I could not find much answer if my boiler would be good enough for an efficient system, so I am looking for some advise. Bought a house recently in the middle UK. 5 bedroom, detached, ground floor and first floor, built in 2009. I plan underfloor water based heating on the ground floor, but so far I only got generic system quote (without plan) from Wunda. Currently there are radiators everywhere, and in general they heat up nicely, so don't think I have much issue with heat loss, but I do not know exactly the heat loss. Floorplan is attached. -Floor: as I know it is beam and block, the closest I could get is an old photo from one of the neighbour who dug it up for extension, it is insulated as I know. Top of the floor is concrete with some self levelling and probably damp proof layer (photos attached) -have wooden windows, double glazed -planned floor type: kitchen/diner/utility and toilet would be tiles, everywhere else laminate -current boiler: Mains Eco Compact, heat only 24kW, manual know to set temperature, so cannot do weather compensation. I think it is on an S plan -heating, hot water: un-vented hot water tank (210l), upstairs radiators on a dedicated loop with a thermostat, downstairs radiators on a dedicated loop with a thermostat, and the hot water tank has it's own valve. One motor. All are at the hot water tank, upstairs. The plan is to retrofit a 20mm EPS system with 16mm pipes. EPS boards would be directly glued to the floor (kitchen, utility has tiles now, they will be removed, everywhere else we have carpet and the image attached shows what is under the carpet). Have a quote for materials from Wunda around £3.6k, this includes 5 zones, with 5x thermostat and floor temperature probes for laminate. -tiles directly on top of the boards -laminate with an underlay directly on top of the boards Does all this sounds ok? Is it ok not to screed it over (that would add considerable cost). What about the zoning? Most of the time the door between kitchen and sitting room is open, as well as the door between kitchen and hallway, and most of the time the sitting room and hallway. I would not mind have all on only one zone, or two, maybe the Lounge on a separate zone as that will be my workplace and I would enjoy 1-2 degree less heat. If no zoning, how the system will make sure that the laminate do not go above 27 degrees C? What about the boiler? Overall I think it is overkill for heating, but that's what I have. Is it worth to consider ASHP? Or a more modern weather compensated boiler? Or just leave all as is, and use the rads and don't install UFH? My partner would enjoy warm feet though... thanks for any comment!