JohnMo

The most space-saving method is to buy a variant of the Zehnder Comfoair that has one internally. In warmer parts of the UK it's often omitted - the unit will then regulate the airflow (or even cut it off) if necessary, which can be OK for short periods. We never bothered and we get -9 for days on end. Not sure preheat is really needed in the UK. The units just slow down the incoming air, which isn't a big deal, when its that cold your house air humidity drops like a stone. Fitting seals to the cupboard door will probably enough for airborne noise, if the door is fairly solid. Vibration could be another problem, depending on what you're fitting it to (floor / wall / material, etc). We have a unit in our hall between two bedroom, mounted on wooden stud walls that are lined with two layers of 18mm ply. Hear when you open the cupboard doors but only then. No worries the MVHR filter deal with this. Not really understanding your sketches? Need some more detail

First before you do anything else analyse what actually happening with the heat pump. Are you getting long run time consistently (more than about 15 mins) or are you getting some rapid on off cycles. or something different? I would look to rationalise the number and size of zones to just a couple. The issue you will have are Heat pumps need flow rate Any heat source needs somewhere to dump the heat generated. Think the current setup is good for neither. You currently have so many zones, that when only one or two are calling heat they are all quite small capacity. If you are happy with current bills and house comfort just repair what you have. If you would like to reduce bills also, I would look to engineer the LLH out of the system, by getting rid of most the thermostats, running a more open system (ideally one zone, maybe 2)

Why, if you building a lean to against the house, yes, but a water proof garage no. Our timber frame rests directly on the garage floors, if it sloped so would every wall etc. nothing would be square. Had lots of garages and never had one sloping. In fact build severe vehicles on garage floors, if they sloped that would be a nightmare.

I would decide what you are doing exactly, then update the current plans and resubmit as an amendment. Then get your building warrant after that is approved. Get your architect sorted, you will also need a structural engineer for structural certificate, if you are changing the structural design and as designed SAP report for the new warranty. Take the opportunity to add an ASHP to the plans, and insulate to death and sort your airtightness details.

Had a look to see what I bought, it didn't say assume non bacterial. Air being supplied is being filtered, so not sure is much of an issue. Extract normally isn't, but we use terminal filters to catch the rubbish being sucked out the room, so don't see where the issue would be there either. Not sure how long an anti bacterial coating would last before it was depleted.

Flat and above ground small concrete ramp up. Never slope a garage floor.

And replacement of bio diverse forest with mono crops, and the huge impact on wildlife and species diversity.

What everyone misses is the electric cost associated with a boiler. So the pumps and controllers etc. they use the electric as a heat pump. Those costs are included in a heat pump SCoP but missed conveniently from a boiler. We can regularly be using 40 to 60W Our heat pump generally gets a CoP when heating of around 4 to 6, this diminishes with standby in mild weather to closer to 3.5 to 4. But as it gets colder daily CoP gets better due to less standby costs. Interesting is a poorly insulated building with a low design temperature will always beat a well insulated house with like for flow design flow temp, because with a well insulated house your standby and DHW generally are higher than running the heating. A hybrid heat wins the day most times. Leave heating system as is, basic heat pump generally about 4kW will do most properties. Heat pump can generally supply enough heat through that system cheaper or as cheap as gas, down to 4 to 5 degs. But with none of the emissions issues. After that you start to get frosty of the condenser and a hit on CoP with the heat pump, so switch over to gas at that point. Very low capital costs, £1500 to £2000 plus a days work. 3 houses for the same as a one house grant.

Tap to the house was almost closed also

If putting water in you need anti freeze, otherwise you may end up splitting pipes if they freeze. The alternative is just air. I used Glycol/water in mine, once pressurised, I left it like that until I connected it to my boiler.

I flushed and filled via a flush and fill valve. Like this https://www.bes.co.uk/22-mm-3-4in-solar-drain-flush-valve-20994/ Used the inlet and outlet to throttle down the flow and have a sub 0.5 bar system pressure while flushing. Initial flush was done on a higher rate, maybe 5 to 6 l/min via a 100m garden hose. But mostly to replace the glycol etc. When I was happy everything was clean, I needed to reduce flow down to about 1 l/min or less to get low conductivity reading, for this a switched on the heating circulation pump and manipulated all three valve on the flushing valve unit, to set up a slip stream through the de-ioniser filter and let it run for about 8 hrs one day and same again a couple of days later.

I recently did a study on HVO (hydrotreated Vegetable oil), not bio diesel, which is full of nasty chemicals, and bad in lots of ways. HVO sounds great on paper, until you start looking a little deeper. So used as a green alternative to diesel, in use almost identical to diesel. Effectively used cooking fats etc. treated by heating and filtering. Tail pipe emissions almost identical to diesel, same soots, same everything.

How is it plumbed in and wired in - sorry not enough info to work with. Photos are always good.

If it's a separate planning permission, to the house not sure you can apply.

Think you can specify either.

Is 250mm the total wall thickness? If so you are only talking adding 50mm? If you are blowing in insulation think towards EPS beads, these will be tolerant of wet getting in the cavity and self drain it away. They will also move easily to fill the whole space.

Spending several £100 thousand building a house, and you would actually want someone else body waste gong through you cellar or even under your house, when it is all finished. Perhaps you need to step back and have a think about it.

That LLH looks nothing like anything Clum sell. Sorry that's bonkers, how can you have 19 room spaces in a 5 bed house? Do some room have more than one thermostat? I would be better looking to simplify the whole system. Are your running costs ok or a big?

Many variables to take into account. Start at 25 flow at 20 outside, then look at your heat loss report and design report, set the other end of the curve to your design outside temp and design flow temp. If house is too warm after 24 hrs reduce the cold end of curve, if to cold increase. Do 1 Deg at a time to see how it changes things.

Our Greenwood CV2GIP, is in our garden room, also, it was also £60 on eBay. It is set on min speed, and completely inaudible. We originally had another make and it was quite noisy. Only thing I have done is take the front cover off to see if it was still running - which it was.

£400 for trickle vents, not anyone sane would accept that.

The fan can go through any outside wall or through ceiling and out the eaves. Ideally as far away from door as possible. You do not have a ventilator or trickle vents in wet rooms. Same with wall ventilator. Trickle vents or wall ventilator do exactly the same thing. Manual trickle vents are not the same, the home owner will just close them and 6 months later say they are drafty and say oh, look I have mould no idea why. There are many makes, some with noise reducing measures etc. Whole thing that makes the system work is cross ventilation. If the double glazing unit is misting between the glazing it's broken. If it's just misty on the inside after a night's sleep, the ventilation is really poor.

So really need install details Radiators or UFH No. of thermostats Buffer or no buffer Design flow temp Make model of heat pump (sounds huge). Heat loss calculations. How is it currently set to run, bouncing of thermostat(s) at a set flow temp or weather compensation? Etc...

Lucky you only have one set of curves, our Atag boiler, had one set of curves if you used their controller, very similar to Viessmann. If you didn't use the controller the boiler had a different set of curves you could use which are numbered differently and start at different temps, ranging from 20 degs to 26 degs flow temp at 20 deg OAT.

Because in years time the drain may be blocked? And how do you then clear it?