JohnMo

We have a smart electric meter - keep being asked for meter reading or get estimated bills, there a complete waste of time.

Recirculation for me. No they don't all have carbon on filters, some do come with, others its an option. There are two types of carbon filter, use and bin or regenerative. Mvhr will do a good job of smells and steam, just put on boost. I don't bother with the extractor if it's just steam, if frying or very smelly I use the extractor and mvhr on boost.

Not mad. If you can get the best insulation you can, get much better than building standards. You would end up with house that cost next to nothing to heat. I found with both companies if you go too custom, the price goes up dramatically. Using their standard designs, with optional best insulation, would give you the least stress. Knowing what you want is key, get a list together of wants, early, prior to tender. Wide door, level threshold at all entry exit points, all showers with completely level entries, all ensuite accessible etc. Don't get carried away with room sizes, go around show houses, see what suits you, measure up

Emmisivity without an air gap is next to nothing. So the foil would act as a conductor anyway.

If you want UFH you need a well insulated slab. A U value of about 0.15 or better would be your target. That would require a minimum of 150mm PIR. Without that you will be pushing too much heat downwards and it will be expense to run. To make running costs of an ASHP viable, the house needs to be well insulated. An ASHP will convert 1 unit of electricity to 3 of heat, but that unit of electricity cost 5 times that of gas. I would do the following Insulation aim for u values of 0.15 or better everywhere. Airtightness Electric or dual water/ electric towel rails, in bathrooms to allow towel drying in summer. Possibly electric UFH in bathrooms, so it is quick to respond and you heat only when needed. Revisit gas move costs, do you need to move meter or just reroute pipes? Look in to MEV with heat pump (link below) or similar. This may have advantages if your house is not airtight. The balance of the heating with IR Radiators, or A2A heat pump. https://kers.co.uk/kers-mev-landing

I did mine very early in the build process and used fibre reinforced C34 concrete.

Aluminum reacts with the alkalis (OH) found in portland cement concrete. When these two chemicals are combined, the reaction produces hydrogen gas. ... corroding the aluminium foil, but mostly causes bubbles in the cement

Have got a gas combi boiler. The thermal store DHW coil is in use all the time and has a temperature control valve prior to combi boiler. In winter I get slightly preheated water in to the combi, to up performance, to as good or better than summer performance. In summer, PV should heat water in thermal store. This removes or reduces the need for gas for DHW production. If the water flowing through the DHW coil is at or above the combi boiler DHW setpoint it flow straight through the boiler without additional heat being added. Boiler is designed to take preheated water.

My build was always going to have a cylinder, to use excess PV instead of export in the summer. So no loss of space in my case. But would not suit all builds.

Using thermal store as buffer, heating it to 40 degs, no issues with short cycling. Houses stays +/- 0.5 degs from thermostat setpoint. So happy enough.

Heating costs should be really low, what ever option you choose. Not sure an electric boiler and wet rads would be on my list. Disadvantages, expensive to run, plumbing. Need to offset capital cost over running cost. I/R Panel heater? Easy to install, thin, quick to operate / heat you. Or A2A Remember you will need ventilation, MVHR, dMEV, or normal extract fans.

"I would not be allowed to remove any of the supplied controls. I can bypass or suplement with as many "toys" as I like BUT if I stop waking up in the morning then the installed system has to be useable." But that's the point, the supplied control made the system work badly. Huge temperature over/under swing. Timers would have to set 12 hours offset from time I wanted things to happen. I have single thermostat in the hall (always on), which calls for heat, or shuts off heat. Bedroom thermostats to make temp lower than the rest of the house, set at 17/18, it works great, they are not allowed call for heat. Set at 19.5, I get a plus or minus 0.5 degree swing, whatever is happening outside. I have no need to mess with the mvhr settings, it just runs at a set speed 24/7, except when boost is on.

Calculate the the surface area of the building exposed to out air temp. If you take the average delta between inside and outside. Write it down. Take your gas consumption, you will need to remove a proportion for DHW heating based on number of people in house etc. Look up for details, but I think it could be about 4kW for 2.4 person house per day. Write it down. Divide the gas consumption kWh, number days then by 24. This give you a number kW you consume to heat house approx. Now divide the exposed area by kW. This will kW per M2., Divide by 1000 to give W/m2. Divide W/m2 by the delta T. This will give you and average U value (but will include ventilation losses, which should be quite small with MVHR). A U value is W/m2.K K is Kelvin. Kelvin is deg C plus 273. But as you would add 273 to internal and external temp, taking the number s as presented would be ok. If you get below 0.15 your ok, if above 0.2, take another look at the numbers especially the domestic hot water use.

Not sure if I right, but I put in a 1000mm square shower tray 20mm high., There a 10mm lip once tiled on floor. But the only shower door you can get (or could find) are fitted with an upstanding strip under the actual door about 50mm high. But is there wording in the regulations about providing a space for... accessibility shower or bath.

We used a normal manifold, spaced UFH pipes at 300mm centres and have the temperature for hot flow at 35 degrees. Easy - way less pipe in floor, comfortable, bog standard bits.

Have you looked at dMEV, easy to install, silent and runs all the time. Just need window vents open or specific wall vent to give good, draft free, cross flow ventilation, you could also include the kitchen in the scheme. No heat recovery though. Or dMVHR, with heat recovery worth reading up about.

We've had really good trades people. We took a punt on the first ones in, they did a great job. We asked the workers in house at the time to recommend different trades that were good to work with, went with recommendations of the trades people in for subsequent trades, without fault they have all been great.

I just used my thumb to push the staples in

You can't staple to EPS, hence EPS at the bottom. If you are splitting use 50mm PIR minimum. Otherwise your staples will pull out.

200mm of PIR would give you a u value of 0.1 or less. If you are using PIR, you can staple UFH piping directly to it. But if using a concrete screed, you need to include a thin plastic DPM above the aluminium on the PIR insulation, to stop a chemical reaction. Finish what ever depth above insulation with a screed of you choice.

say 4 degrees delta T below 30 degs (second post down)

From what I've seen it just ups or lowers flow to keep it the correct delta T

Mines at 300mm spacing, over 190m2. Lounge has two loops, the other rooms a single loop. Total 404m of floor tubing. Low energy house though. No issues, UFH flow temp at 35 degs. But closer spacing, can run cooler.

Neither are massively efficient, some websites say the vogue is now discontinued? Why ask for an A+ rated boiler for example an Atag iS is the same price as the lower cost one.

CO2, has record 24 hr average, current, peak in last 24 hrs