JohnMo

Your architect should have to deal with sort of thing on a daily basis. Ours had a go to man, your should have the same.

Let's start with basics. Have you done a detailed heat loss calculations? What are your U values for floor, walls, roof and windows? We have a 6m high lounge and all other rooms go up to about 3.5m, we don't struggle to heat the house, with UFH. A heat pump heating system is fine as long as you design for low temperature heating.

By EWI do really mean external roof insulation? Or something else. Are you building a hybrid roof? If so have you done an interstitial condensation calculation? If you panel over the whole lot, then add additional wood below. All would be secure, knowing everything is held in place correctly and you will end up with the same effect. I think if your not careful something could land on your head in 10 years time.

Good observations. There will more issues now electric vehicles are becoming main stream. Most repairers not being suitably qualified to touch the high voltage side of things. The mainstream workshop not having a scrubbie where to start. The same is mostly true with heat pumps and more generally for any low temperature heating system, especially when also coupled with a low heating demand house. Everything they have been told for years, is now not really suitable or not going to work efficiently.

The design for gas boiler is usually for a high temperature system. You can design it for a low temperature system (as ours is), but this totally confuses the normal plumper. But a low temp system is the same design broadly, the delta T can be the same for both a gas boiler or heat pump. Our boiler at 25 to 30 degree flow temps does so with a 4 degree delta T. Our heat load is low so the pipe sizes can be normal sizes. Most gas boilers in a low energy house will need a buffer to operate without short cycling, not just heat pumps. The trouble is to rejig the existing fleet of gas or oil boilers to run low temperatures; to get condensing mode all the time, a lot of homes would have plumbing of too small a diameter to get the mass flow through the system, at the required temperature. Plus they would need new radiators, new controller and a good possibility those with system boilers couldn't do low temperature for heating and high temps for DHW heating. So isn't a easy fix. Hybrid systems do work, but reducing heat demand is the real fix all.

Was looking to go fast track G99 route, with zero export inverter.

I only have 3.1 kW installed, but have a garage begging for some to be installed on it. Prices are too high at the moment due to a high demand and demand v supply issue.

Couple of issues I see first off. The 3 zones, will play havoc with either a gas boiler or heat pump. As your heat demand on any one zone will be really low, a big buffer will be required for either system. Our heat demand is similar to yours (slightly higher), the min turndown on our boiler is 6kW, with a max demand of around 3kW (no sun, -5 degC). We installed a 180l buffer. We went with gas, as at the time I couldn't make the numbers work for an ASHP, with gas on the doorstep. Still can't really. We have a combi boiler, that can accept pre heated water. In the summer excess PV is diverted to the immersion in buffer, to heat it up, a DHW coil in the buffer heats water up on its way to the combi. A solar diverter valve is used, if above 45 degrees, water goes direct to the tap, if below 45 the water goes to the combi for further heating. Works well, our gas bill for the last couple of months has been mostly the standing charge. Couple of different ways you can run your heating, dump heat into the floor for about 6 hours, the heat will then trickle out over the next 18 hours, then repeat. Or very low flow temp constantly. The call on gas or electric is your to make, any system can work well, as long as thought goes into the design of a low temperature heating system. Then the system is pretty much future proof for any boiler design.

So you could use something like. These are 25mm deep. 16+12.5, gives 27.7 height, if you are using 15mm plasterboard then 31mm height. https://www.toolstation.com/enlite-slim-fit-round-low-profile-led-downlight/p56573?store=LJ&utm_source=googleshopping&utm_medium=feed&utm_campaign=googleshoppingfeed&mkwid=_dm&pcrid=&pkw=&pmt=&gclid=Cj0KCQjw_7KXBhCoARIsAPdPTfh3zjexFfspXlESIQ7o08bNkmHonb00JmuXlD4QTK_uFsPn5L0xW5caAsd4EALw_wcB&gclsrc=aw.ds

You get down-lights that are about 15mm tall. A service batten 50mm tall will be enough space for the little control box.

my floor build-up is slightly different from yours - concrete, insulation, concrete, rather than insulation then concrete. But I ran all the cold water to the different rooms, from a manifold below the insulation. Water is always cool, great for drinking. Building regs say the pipes have to be removable so I used pert-al-pert in conduit. So far no issues.

Not sure about that, MCS best practice guide consists of about 25 pages of technical bits and 40 odd pages of contractual stuff.

It's worth a look https://www.heatgeek.com/find-a-heat-geek/

I think if you wet it first with water, things stick much better. Recently stuck stone slip to aerated blocks, it only worked if I wet the blocks. Think they suck the moisture from the cement be too quickly, so it doesn't dry correctly, so the same would be true of plaster.

Think the problems may stem from a lot of monkey see monkey do, the trainer is giving a set syllabus and may not be that well versed in thermodynamics, have little or no understanding of when zoning is or isn't appropriate or the reason why. Or for that matter how to get a good CoP from a HP. Trouble is you can get away with a mediocre gas boiler installation and no one knows any different as gas is cheap. A mediocre HP install can have a bad CoP, electricity is expensive, so end with a big bill each month.

You need reduce your pressure drops to/ from the outside world, so the size will depend on the length, number of bends and flow rate. As you say for now 200mm would be ok. I inserted plastic tube through the ICF, leaving an overhang either side of the wall and foamed into place and when I did the concrete pour the concrete just formed around it.

I think the quality of general training on heat pumps for plumbers is almost non existent. Heat geek, do specialist training and have a database of people that have passed their training (as opposed to just attended). So may be worth a look. The basis of any good heating system starts with a heat loss calculation. You say you have paid for a design and supply, so assume you have the heat pump? Is this for a new or existing property?

Forgot to add a note about my system, your combi has to be able to accept pre heated water at around 43degs. Most modulating boilers will, but some don't. So you need to check, not always that easy to find the info.

But if the comment is applied to post above mine, where the inlet of the MVHR is to blocked, so it becomes a recirculation system, it is no longer MVHR and due to the flow rates a rubbish Aircon unit. So not fit for purpose. In a residential setting I have never seen Aircon that replenishes the air, just moved it through a heat exchanger with a fan unit.

Level in expansion tank would only drop if the central heating system is full of air. Inadequate ventilation would be my guess, high humidity area around tank, has he checked the eaves vents are not blocked with insulation? Feed pipe to F&E is supposed to be a vertical pipe, so will always transfer some heat. You can install a cylinder in a loft, but heat losses in winter would be quite high and all wasted.

I would agree an hourly rate for changes ahead of signing any agreement. Things like double plasterboard should be decided well ahead of a build starting. My view is once build has started the only changes are when there has been a real mess made of a design aspect, so the there is a material clash and something cannot be constructed. Thermal insulation sound transmission should be fixed and not changed at the design stage.

Just had a look, daily costs of around 40p mentioned, which is high. Carbon filter flowed by ION exchange resin and then a post filter. I am using a BWT AC002200 Combi Care Polyphosphate Scale Inhibitor. About £30 per year for a new cartridge. just installed it upstream of the boiler.

The PIR I got came direct from the factory, manufactured two days before. All the Rockwool came from a builders merchant just down the road, for a third the price of me going to builders merchant direct.

I got all my insulation from insulation hub, mostly with free delivery to Elgin. 145 sheets of 100mm PIR, for £3500 two years ago, just looked the same stuff is £5500. That's a lot more expensive.

I got both my units off eBay. A HRV10M and a 1.75, for £570 for both units. Both new and unused.