JohnMo

If you do proper Weather Compensation the circulation pump is always on (no thermostat) and with UFH the floor surface temperature is pretty close to room temp. So if floor temp on any given day is 22 and the room 21, heat is given to the room, however if the room gets solar gain and goes up to 23, there is a negative dT and the floor actively takes heat away. This heat is seen in the return temp back to the ashp and the heat pump modulates its output down. WC does that as a matter of course also - circ pump is always on, if you want. The upper grey line on the below chart is circulation pump flow rate. Attached a 10 to 13 deg day, 24 hr snap shot, the highlighted area is DHW heating. Zero control except target flow temp, and compressor start and stop hysteresis. Circulation pump is on, it just changes speed as required. Space heat CoP is 6.2 running at around 10 degs. Whats not to like. As it gets colder the cycles become longer, even on a day where heating wasn't absolutely required, no cycle times were less than 20 minutes on.

Same theory applies keep the heat low in bedrooms, don't put radiator on or leave them on low, keep doors closed. Works ok in our house. If you want even temps leave the door open. If you want it really cool (needs to be cool outside) close your bedroom door and open a window.

Lost interest in reading the report when it quoted saving over a £1000 because you have solar. Most your energy costs occur when solar output is rubbish.

Correct, but does form hydrogen so you get small bubbles of hydrogen form. That's the only reason you do it. It also prevents the ham fisted screed operator getting screed under the insulation.

On a single zone it shouldn't be an issue as there will always be (or it's all off) flow through the UFH and radiators, so you cannot get reverse flow.

Gaps make the insulation a waste of time, bit like a cup with a hole in it. You will be amazed, you have to knock the insulation in place because you have made it a tight fit, next time you look you will see gaps. Taping is belts and braces, if screed does get under the poly sheet and into a gap the whole floor insulation can lift. End result, screed under insulation.

Aren't there rules about party walls and noise mitigation that requires a load of insulation adding to your side of the cinder blocks? Don't you have plans? Wouldn't you need planning for a loft conversion and to add a dormer?

You don't mention heat pump size? How long are the primary pipes to the diverter? How far to your cylinder from diverter, what size pipes? If you are starting a scratch install of a heat pump, you really need to doing at as low a pressure drop as possible. 22mm primary pipes - do you have a buffer? You need to give us a lot more details.

More insulation the better. Go PIR for all of it at 150mm. So Celotex or similar. Tape all joints, foam all gaps, add a 25mm minimum upstand all round. Prior to screed a thin polythene membrane on top to keep the cement in the screed away from the aluminium on the insulation.

Just to provide a bit more detail -MEV and dMEV require trickle vents to be open or self modulating to provide sufficient cross flow ventilation. Testing was completed by BRE and many councils and shows without the trickle vents open unhealthy CO2 concentrations will existing bedrooms etc. This may not be the case with intermittent fans.

UVC will provide a shower experience way better than a normal combi boiler. I have had both in the same house. Water gets to the shower quicker from opening the tap, flow rate is higher. If you have a storage combi boiler the experience is similar. You do not need a pump. An UVC should be delivering water at 3bar. A vented cylinder will be around 0.5bar depends entirely on height of the overhead tank, that's why they need a pump for a decent shower experience.

Air tightness is all about details. Builders will do what is asked if them in general. If airtight details are not specified, you will not get them. This includes how window and doors are installed and then sealed in place. Are joints between sip of panels taped etc... Be careful with aluminium windows make sure you get the UW value from the supplier. Some are absolutely rubbish. Scottish building reg mandate MVHR is airtightness is 3 or better, MEV or dMEV for above 3 to 5, what ever you want after that because it's drafty. There have been studies that looked at it also they concluded similar. I binned all my references when I changed my phone

Not best location, keep inside the heated envelope. You also need good access to service. It's pretty much mandatory to sound insulate all internal walls. Mine is mounted on a stud wall in a cupboard between two bedrooms. Did two layers of 18mm marine ply to mount it on. You cannot hear it at all. It's not an ideal location next to bedrooms, MVHR is only one noise source. Your architect should be discussing with you and it should be clearly stated on the house specification and drawing. If you are not going airtight better than 3. Don't waste a load of money on MVHR, do MEV or dMEV with demand activation controls. MVHR requires airtightness or it's just another draft, that costs quite a bit to run, for a negative impact on heating costs - not a positive one. As mentioned all this should be sorted at and defined as part of the design stage. Adding and changing stuff, without a sound strategy, is a good way to waste lots of money later.

I would keep it simple, just run 28mm Hep2O, then without working anything out it will be fine. You also have to allow for the pressure drop through the UFH system as well.

No If you are doing 14 l/min and the limit is close to 32 l/min, you have no issues. m/S is velocity l/min is a volume flow - so very different units.

It's about not depressurisation of the house and carbon monoxide spilling in to the house. It a health and safety issue. An unbalanced MVHR system is just a consequence and really doesn't matter. Not really about what I liked, it's about what you like and suits your home, just make sure primary and secondary are supplied via the inlet duct. Many makes and models don't. I went HETAS, registered for ease of compliance. They also sweep the flue and service annually to keep the right side of my home insurance.

Flexible 110mm duct isn't too bad, still big but better. I just did a shallow U shape, so I can vertical up the walls and a 90 Deg elbow to take me through the wall.

Wasn't convinced the commercial twin pipe was that good, that's why I did my own, each pipe in its own 110mm duct with 25mm wall thickness insulation all around. Also penny's in the pound cost wise. So only has approx 15mm insulation horizontally. Although there is quite a bit vertical, think the losses would just go sideways.

I am using 22mm plastic pipe from my UFH manifold (location of the diverter valve) to cylinder via CCT and additional pump. The pump on the ASHP delivers 1.5m³/HR doing hot water. From measuring flow temp temps, even with CCT pump at full speed I cannot get the same volume through the 22mm, as the ASHP delivers via 28mm. 28mm is circa 16 to 18m each way, the 22mm is about 10m each way. Just use 28mm like a sensible person would. Your pumping losses are going to more than your heat losses.

Page 86 of the attached manual, top of second column of text. Hep2o_Parts_Users_Guide_Australia_2018.pdf

That is more than my whole DIY retrofit cost.

Read up on Buildhub, not the best reputation. I really would do a heat pump cylinder 3m² coil or bigger. CoP of 3.5 should be a regular. Pre plumbed is a waste of money. Do it your self, get a Panasonic monobloc. Slimline cylinder. No need to solder, use either Hep2O barrier pipe or copper or a mix. Use Tectite push fit fittings for the copper and Hep2O for plastic and copper to plastic. Do all as a single zone, no buffer needed. So heat pump to diverter valve. Diverter to top of cylinder or heating system, the two returns tee together back to heat pump. Power to heat pump wiring between ASHP and controller.

Nothing has zero tolerance. Building regs has a minimum and maximum height those are the tolerances. So no less than or no more than. Unless a client supplied drawing states something about a tolerance between fittings heights in different room?

Slight correction - it's not an unvented cylinder as such, as it contains heating water and uses a coil to produce hot domestic water. It is more closely related to a thermal store. So does not need to comply with G3 regulations, where as an UVC has to comply with G3. Also the OSO cylinders although good, don't have the biggest coil, which put me off. Also the increased price for vacuum insulation is very high.

Like it - a man with a proper plan.