JohnMo

We used proctor Roofshield, it's vapour and air open.

The system just uses people that are happy to cut and paste - sh!te in st!te out. Many assumptions made, but you pay maybe a £100 or less for the EPC - but to do the EPC correctly would take tens of hours. What can we expect? Just treat as a tick in a box and move on would be my advice. Keep your electric bills for a future buyer - way more important than EPC.

Have tried it not ice cold - yucky

Good - go with 150mm. But stuck with 100 and 50mm. 150mm are a pain to install well. Stick with PIR at that depth. You 50% more depth of polystyrene boards for the same U value as PIR. A blunt saw is good for cutting PIR. Foam in any gaps. Stagger joints between layers

Both will be equally slow, which is the whole idea of UFH. Unlikely to be any cold spots - but a floor well put together isn't hot either. Many because most if not all the time it's actually cooler than your body so will never feel hot. I assume you have thought about and installed plenty of insulation under the UFH pipes?

Me I have no glycol, it was removed. So just the two chemicals mentioned above and 2x anti freeze valves (required for ASHP warranty). Quick bit of research The Sweet Spot for bio film formation is 20 to 40 degC: Most common bacteria (including pathogens like Pseudomonas or Salmonella) thrive and rapidly create dense, stable biofilms in this moderate to warm temperature range. Optimal growth generally peaks around 37 degs. Extreme Cold (< 15 degC): At lower temperatures, microbial metabolism slows down. Biofilm formation takes much longer (often weeks instead of days), though the resulting biofilms can be highly resilient and adhere strongly.

If you already have the UFH why are you going MCS route. A direct cylinder excludes you - regs state the DHW has to be heated via the heat pump to get the grant. Upstairs emmitors are not needed as long as the UFH gives enough heat to the house. This is a confusing statement - who said you weren't eligible? Your heat pump needs around 20L per kW at min modulation. So should only need about 40 to 50L in your system. Running a single zone that should be easy to achieve without the volumiser. Not a fan of the MCS fan, many people seem to get royally ripped off. I am using a Haier R290 4kW heat pump (but fiddly setting up for best efficiency) but runs great, £2400 including vat from Wolsey plump centre. Pipes through wall direct to UFH manifold is a simple install add a couple of antifreeze valves and isolation valves plumbing all done (expansion valve and pressure relief in ASHP), comes with the correct strainer to add to the return line.

I would be very careful having a ducted ventilation system (MVHR) up and running with dust making works ongoing. You would be amazed at the amount of fine dust that will start coat the internal of the ducts.

So if cooling or low temp UFH the majority of the water stays in the UFH while you do DHW. A heat pump either does DHW or CH not both together. At the end of the DHW heating cycle you get a slug of hot water mixing with CH water, which is diluted very quickly when mixed with the UFH water and or fan coils. So the DHW demand, does little or nothing advantageous to preventing bio growth. Best case you will heat the DHW circuit up to about 55 degs, but temperature is not held long enough to pasteurise the water, so really had little or no effect. It may even increase the bio growth by pushing water temp to a more ideal temperature. For the sake of £30 I add biocide, it's cheap insurance, from issues later.

I bought a Aldi impact driver, figured I would only use intermittently, was a billy bargain price, with 2x battery and charger. Has performed very well and got used way more than I expected. Is quite capable of driving 10mm x 140mm coach screws, without any complaints.

Biocide, if a low temperature system add biocide, if used for cooling add biocide. Use same make as the inhibitor so biocide and inhibit from same ame manufacturer), so there are no compatibility issues. I used, Adey MC10+ Rapide Underfloor & Central Heating System Biocide, plus Adey MC1+ Central Heating Inhibitor.

There are specifically tools for the job. This basically a slide hammer and pincers in one. https://amzn.eu/d/0jgJMtLC

Depending on batten sizing and if ring groove nails used - you may do more harm than good. Could you simply add more battens? It may be faster, less stressful and less rework.

Think the reality is most modern heat pumps don't vibrate. I have Flexi hoses, but more to allow small movement due to wind etc. but possibly not needed. It also give some assurance no noise is transmitted. Bit like buffers and glycol, none of that needed either, install antifreeze valve that reference water temperature (not air temp) your all set. All old rules from single speed compressors and fans.

True, but Ideal don't do cooling, so that was eliminated. Vaillant, just too expensive, but they do seem to perform well in real life. Mitsubishi never really liked and most don't cool. There are a few other British made heat pumps, but none of them do cooling or are stupidly expensive. My driver for a heat pump was cooling, heating is a bonus.

Due to instability caused by heat pump hunting, I had to make some slight changes. Using the thermostat for heat pump permissive, the hysterisis was widened to 0.3 degs, the WC curve was changed also, 26 flow at 10 degs and 29 at -5. This seems to give a good balance house temperature and running stability leading to great CoP. Have run cooling also, have set target flow temperature to be 14.5, this was giving a CoP of around 7 in the warm spell a few weeks ago and zero condensation. Overall with cold spell over the last week, we got an average CoP of 5.4.

Actual rules say calibrated and certified equipment. But I used the same person that did the air test as he did MVHR commissioning also. But everything else was self designed and installed. Pretty easy once you get your head around it.

I did look harder and dismissed G4 for both supply and extract as that is not the normal offering, for a new unit, it's the supply filter that bumps up the cost. But OP wants to go MVHR route anyway. But here is a proper study completed a while ago, worth a read for anyone interested. Atamate_SDAR+Paper+2019+(1).pdf

Your preferred Brink MVHR, filters from a quick look are £70+, depending on area you live, that could be twice a year expense. So may only take the time it takes to make a cuppa, but it becomes an expensive cuppa. Had a dMEV fan running in a summer house a couple of years, nothing has been done, nothing has been needed, could replace the whole fan nearly twice for the cost of your filters. MVHR isn't the only solution, and not always the correct or only solution.

Absolutely nothing wrong with a dMEV system, what maintenance, there is none? The trickle vents are controlled by a membrane that contracts or expands to variable moisture levels, zero inputs from anything else. The fans are commercial available bathroom fans. Greenwood make a nice one, but many others available. Way less maintenance than MVHR. Zero faculties needed, fit it walk away. That cannot be said or MVHR as you need to change filters etc. Same as any other house, I have owned around 10 houses, no one has ever told me anything about maintenance ever. But as said above dMEV, what maintenance?

Ours is nearly 200m² on a single floor. If you are looking at anything near that cost I won't thinking again. If our target airtightness had not demanded it (Scottish building regs) I would have gone dMEV or MEV. Very little in it, heat loss wise. dMEV demand based system Wet rooms, Greenwood CV2 one in each room including kitchen. Or central MEV with humidity activated terminals and constant pressure fan in MEV unit. Automatically and smartly do boost it needed, run at a very low flow all the time. From eBay look at around £40 each, for Greenwood CV2 fans, almost silent, draw almost no electricity, zero maintenance. No trickle vents in wet rooms. Dry rooms, trickle vents that is humidity activated (can include acoustic damping if you need) around £60 to £120 each. Can be through wall or in window. How it works, day time, bedrooms not used, trickle vents almost fully closed. Downstairs rooms have people so the vents start to open in response to rising humidity, fans draw the air across the room, through corridors and out the house. At night the effect swop, now bedroom trickle vents open and downs close. No-one in house, all trickle vents go to min opening. As with MVHR you have internal doors under cut around 6 to 10mm

My first quote 6 years ago was £10k - bonkers. Ended up DIY and spend around £2k

So not much then! Don't they also build things twice, first time as a proof of concept. Then there are all the other parts of the plant all nice thick concrete.

That's a long design life for industrial equipment. Nuclear design life's for equipment is generally way shorter than the same piece of equipment in general industry and it's maintained multiple more times frequently. Think the issue with nuclear plant design is the reaction containment and it's certification. The balance of plant i.e. Pressure vessels, steam turbines, water pumps, piping etc will be overhauled and recertified many time in 30 years plus, with the pressure containing parts regularly recertified, following inspecting for cracks, material loss and wear etc.

Suppose depends if you call it PV or black glass fence panels. And how you interpret permitted development rules on area for a ground array, is it ground area or panel area. 16m x 35mm isn't much ground area. Do it in bifacial panels, so it looks pretty (black glass) both sides rather than black glass one side and white plastic the other.