JohnMo

Info on cylinder heating from A2A https://youtu.be/9domQlKtbBQ?si=qnuT_Y9UgAR-zfUs

You can (you need to do some searching) get heat exchanger modules for A2A that allows you heat a water cylinder. Have a read on this thread https://forums.moneysavingexpert.com/discussion/6414827/moving-from-nsh-to-a2a-heat-pumps

But tight enough to warrant MVHR is another question. Think BR is pushing you to have an airtightness of 8m3/m2 to scape a BR pass. You really need to be a third of value to warrant MVHR. Which unless you build with that in mind will be difficult. You would be better planning for MEV or dMEV, but with humidity activated trickle vents and humidity demand fan speed. Are you talking about a heat pump cylinder or just an immersion cylinder?

Are you planning on being very airtight?

This (above) would indicate you have no flow and almost no heat. Are these reading still true when flowing?

The wall can be built up to 2.5 metres (ten courses) in height before the first concrete pour. This bit has changed since our build, it was 6 rows when we built. I would ignore and do 6 rows at a time. It way more manageable and less likely to go wrong.

Thing I missed, when it's wet and there is a freeze overnight, the floor takes days to defrost, especially if you are well insulated and no side thermal bridging.

You need priory demand hot water (PDHW). Read your manual it may be equipped with most of what you need or some options may need adding. Search for PDHW on Google and have a read up. Avoid S and Y plan. Or a simple add on kit. https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://www.ephcontrols.com/section/pdhw/&ved=2ahUKEwikra_CwYuKAxVtWEEAHZmoAr4QFnoECEEQAQ&usg=AOvVaw1ZNV4XzRVOTkPHFUHziTIr You can also DIY it, with a resistor and a relay also. Basically you fool the boiler into thinking it's running weather compensation and break the signal (with relay) and the boiler moves to normal mode to heat cylinder.

Concrete, not really screed. We did a quite high slump so it could be pumped. You need to have all drainage pipes positioned for toilets, sinks, showered etc. I used waste bits of 100mm thick PIR as formers to exclude concrete where I was uncertain, back filled later as needed. You need any block work in place up to finished ground floor level. You need to pre-position UFH manifold. All pipes need to be protected from freezing if the container water. So either air test or water/antifreeze solution. Do not let UFH pipes goes under walls, as you are likely to someone put a hole in the pipe. So photo, all the wall sections are removable and we're moved during the job. Have shown, UFH manifold, main electrical cabinet and floor formers to exclude concrete. We used a pump to get concrete from A to B.

That's a lot of heat your adding via a2a. Think (know) you need to do a heat loss calculation. Your biggest issue will be a sensible amount of modulation. Are you planning a multi outlet with one outdoor unit? Why not just UFH and an a2w hp?

Good observation if building a block of flats. But really that the same thing on a 1 or 2 storey building. Different fire spread mechanisms at play, due the heights being different.

What are the red flow meters showing on the UFH?

You have written the steps you did in the first post. The main thing you have done I assume you took a note of the setting before you started fiddling? Confirm. Can you set them back to where they started? Can you set the flow rates to each loop to 2.5L/min? Is one or more loops achieving flow? Are all or none achieving flow? Those not achieving flow are likely to have air trapped and they need bleeding. While doing this monitor the kW on the heat meter (Sonometer) and report. The heat meter will also tell you flow rate, and temperatures, just press the black button and it will scroll they different readings

Converse to the above, my pipes are not insulated in the room and I have no condensation drain. But I flow at UFH (cooling) flow temps, over a long period - so above dew point. Certainly not as effective as really cool flow temps, but acceptable

Ideal answer is yes, then you can flow any temperature you want, without concern. If you are also flowing through UFH loops, you can get away without. All really depends on flow temp. Risk free answer is you need drains

We have a steel frame at the front of the house buts mostly to hold the glazing, and a big roof overhang - original design was all wood, but was way to chunky. There is no other steel in the house. Our living room is just over 6m wide and about 6m tall. Big glulam beam, posi rafters at 600mm centres. Part way through construction

Have you been through all the documents they have on the website. There's a tonne of information including archive stuff. If you can find one registry, would think they wouldn't go to the effort and changing it between different models. But since tweaking down the flow rates after official commissioning, I haven't touched the MVHR except filter changes and a bit of cleaning. It doesn't boost anymore, humidity just doesn't rise enough. I would really leave it alone as you end up spending way to much time fiddling for zero real benefits. I found a mold indicator in home assistant, so set it up the other day. Almost zero chance of mold. Steady house temp, 3G glazing and MVHR set to just below passivhaus rates (based on area).

I did look at those, when I was planning, then decided not to put heating and ventilation in the same package, so kept ventilation and heating as completely separate. I think they can end up as normal ventilation with heat pump off and additional boost ventilation when the heat pump needs more energy. So robbing house air (with attached energy) to satisfy heating demands - so robbing heat to provide heat

What happens when the heat pump is idle, assume the ventilation stops? Or would you have MVHR/MEV and the outlet air feeding the exhaust air hp?

If you know the space a closer takes up. But as mentioned get them to measure, you are also making them take responsibility and take the risk. No idea of the window quality or cost, but generally not cheap. If they can't or will not measure, go elsewhere.

A sketch may help, to visualise more clearly.

Yes. This is it going on You can see the brushes we used to apply in this photo

That is how I did mine, think I use 3 soft building sand, 1 cement and some lime. Mixed with water to double cream thickness. Then used a soft broom. Brushed in until I could see no more holes visible. Mine was on wood Crete, so way more difficult than blocks. I also used a hybrid sealant around the gaps between wall and wood as belts and braces.

If you draw out, what you mean, that would be great. The wood and PIR packing is just acting as packing, doing very little insulation. Your yellow beam horizontal parts will be the same temperature as outside and they are bypassing all insulation.

Not really difficult - say you supply 50 l/min at one point, where does it go? It has to go to extract points, so if you have follow the air route. Ideally it will travel across rooms halls etc. Read up on coanda terminals, these will push air across the ceiling in a chosen direction, extract ones will suck it from a direction of your choosing also.