JohnMo

Count to 2, have a cuppa or go to pub while other person continues drilling the other 19 holes. Then if surface mounted the plasterer say what numbty put all this pipes here

Still have the same amount of manifold outlets, without the faff of punching loads of holes through between floors. Two holes job done. If you 21 pipes between the upper and lower floor you already have way too much complexity. So saying 21 pipes between floors is not complex, seems a stretch

Just choose a wireless thermostat that switches between cool and heat easily - I say wireless then you can move it to where it gives the best representative house temperature. But the Panasonic controller has one built-in (pretty sure), just use this. It should do cool and heat out the box.

I would simplify. Why not do 2 up and 2 downstairs (1 each hot and cold). Then a single 15mm between each manifold. To make it simple, we do one 15mm to each wet room from each manifold, then branch from there in the wet room.

We used an external permissive to start stop the ASHP. So similar to what you propose. For me knowing what's going on is important, so I have used a wiring centre for the UFH, this is equipped with room sensors, not thermostats. The signal from the wiring centre goes directly to ASHP, not to UFH actuators etc. The whole system can also be moved between heat and cool via a volt free signal. So open circuit is heating mode closed is cooling mode. ASHP using the same signal, so use a single switch to move both the UFH wiring centre and ASHP between the two modes. We have in effect two heated areas the house and summer house. After quite a bit of experimentation figured I could run as a single zone and either the summer house or the house could call for heat, and both got heated together. The house floor acting as a buffer. Running for an hour or so to heat up the summer house has zero effect the house. Have run pure WC and if you can do that, I would, but we have found using the wiring centre and it's sensors, giving the heat pump permission to run, meant we ran better and could keep away from min modulation longer and regularly get CoP of 5+. I would try to run as a single zone, decrease the upstairs output with reduced loop flow where needed. You are going to running very low temps, our curve starts at 26 degs at 10 Deg oat and goes to a massive 28 at -5 degs. So likely hood of overheating is zero. I would make sure price wise you are not being screwed over So MCS uplift and plenty with a profit to make

I needed to top up the system and decided it was too much faff keeping to VDI2035 specs. So dosed with Adey MC1+ inhibitor and biocide.

But for 90% of housing stock they will not be drilling into walls to find out how construction was done or any improvements completed in x years. You may be lucky and they will poke their head into loft, if it has a suitable ladder. They will make a huge bunch of assumptions. Funny old thing just like MCS assessments for heat pumps. We have to most of that now in Scotland, as we need an as designed EPC prior to Warrant issue. Getting those details for existing housing - 90% of the public would not reply, as it's all stuff for someone else to understand.

Neither did we

More complex but will still be sh!te in.... Same monkeys will just use a different computer program.

We used proctor Roofshield, it 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.