SteamyTea

I worked, as a manufacturer, in the health and leisure industry 30 years ago. A few suppliers set up an organisation called the Fitness Industry Association. This was on the face of it to ensure high quality, but in reality it was to hamper some people in the industry from selling. Was totally crooked.

Yes it is. Working out heat losses is not that difficult, but it is very boring. Basically a case of finding out all the wall, floor, window, doors and ceiling/roof thermal properties (the W.m-2.K-1), all the areas, and an assumption of the weather extremes, as well as any temperature differences between rooms. Then the power loss from the air changes has to be added, and adjusted for the MVHR. Then the water usage is added, but you can probably work that out pretty well from current usage. There is a spreadsheet floating about that is pretty accurate. Search for @Jeremy Harris as he created the spreadsheet.

How accurate do you think this is?

Don't let the Architect fob you of with a minimum level. With UFH, because there are two temperature gradients either side of the pipes, the losses to the ground can be quite substantial. You also have to be wary of cold bridging around the periphery of the building.

Welcome. Passivhaus standard is quite complicated and finickety. Getting to the thermal loss standard is not that hard. Just a case of reducing losses and limiting inputs. The easy way to reduce thermal losses is to insulate and try to eliminate uncontrolled air losses. Now you say you want to use the existing slab, how are you going to insulate it so that it is suitable for UFH i.e. 0.15 to 0.2 m of insulation before the pipework and final floor finish. As you will be building under the latest regulations, how are you going to design out overheating (Part O)? Many people like large windows, but they are probably a thing of the past now. But that can save you loads of cash. Do you have enough space for a sewage treatment system? Where are you putting your PV if it is limited to the 9m2 ground mounted limit, why not on your roof? MVHR is, as mentioned, a stand alone system. Forced heating, it is not, though it can be designed to be both. If an Architect says something i.e. systems talking to each other, then start some proper research, there is probably a mate in the background that has a solution, at a much higher price. I can fit my bike in the back of my car, and they are both transport systems. That is where the similarities end. As a general rule, a house is a very basic engineering structure, just complicated by legislation and a disjointed industry. As @ToughButterCup says, break things down into simple questions, then find the solutions. @pocster is a (expletive deleted).

I think there is two issues here: How it work. Making mine work. I am sure your local agricultural college will have an expert on AD, it is becoming all the rage now, even Farming Today (which should really be called Middle of the night farming) was talking about pig poo and stuff this morning.

I have been grappling with this problem for over a decade. Even at our current inflated energy costs, I am still better off just using E7. Yesterday, with just the smaller storage heater on, usual daily use and a go with the washing machine, I only used 9 kWh. Come the summer I will be down to between 3 and 5 kW/day. For me, it is just not worth putting in PV.

Not really, for the reasons that @joth has said. Why there should be a lot of effort to get uncontrolled air leakage reduced.

I was in the dog(house) last night.

As a general point, MVHR, or any extraction system, adds to the ventilation losses. So if a house has an ACH figure of 4, and the MVHR/ESHP changed the air every hour, then the total losses are 5 ACH (or whatever the numbers are). This don't matter much in the summer, but may well affect overall usage in the shoulder periods, like now (end of March).

An oil boiler is either on or off, an ASHP can run for prolonged periods of time. So you may find that your current radiators can deliver the required energy needed, but at a lower flow temperature i.e. 45°C. Just a case of working it out.

I have never run the numbers, but generally, when temperatures are high, so is the RH. Condensing water takes a lot of energy. 2256 kJ/kg. Water between 0⁰ and 100⁰C is around 4.18 kg/kg.⁰C. Quite a difference, even allowing for the relatively small mass of water present in a kg of air.

Yes. as you say, it boils down to the efficiency in the end.

My feeling is separate is better, Space Heating is at different times, at a different temperature and for a different purpose than DWH heating. Bit like buying a RangeRover and hope that it can pull a plough occationally.

Yes. With a bit of imagination they can be effective. If they cost the same as ten years electricity, about $1640 at my current inflated rate, I would consider one. "Rich man sweating in a sauna bath, poor boy scrubbing in a tub" "Me, I stay gritty up to my ears, sitting in a puddle of mud"

All you need. Stick to comedy for the podcasts. https://www.bbc.co.uk/sounds/brand/m000dpqn?partner=uk.co.bbc&origin=share-mobile

I find books better.

Exhaust air heat pump. It is like a normal air to air heat pump, but extracts the air out of the building to heat water. The problem is, the air in the building has to be heated, so can become very expensive if the heating is electrical resistance. Some on here have used them to good effect though, especially if it is integrated with the ventilation system and DHW usage is relatively low, in proportion to the building volume. DHW usage is really a function of occupancy, more people, more hot water used.

Discounting devalues. We don't drop our prices, even at the height of 'influencers' after a free meal. I vote with my feet, if something is not worth the money, I go elsewhere.

That is about 11 kWh. Say timber has an energy content of 4.5 kWh/kg. 2 kg is 9 kWh. I suspect your cylinder was not at 22°C.

Interesting as my mother's meter, with EDF, is blank. It has not been changed, but they know it is faulty. I am leaving it a bit longer so that from my complaint, and arrangement to change it, is over a year old. Thames water do not know where the water meter is as well. Arranged to get that sorted but no one turns up. House is empty now so bills are minimal.

Ah, the unknown that makes Britain the most productive country in the world.

You got further than I did.

Aerogel from wood. https://www.nature.com/articles/s41560-023-01226-7

Tell him if he works hard he can retire at age 64.