JohnMo

The bend supports are just that, depending on what pipe you are using it may be helpful to use them. With something like Pert-al-Pert, which forms its own bend they may not be needed. If you want to add something, some flexible electric conduit could sleeve the pipes, 20mm conduit should be ok.

So where does it say that in black and white?

Plus structural engineer says NO. Interesting product, but if the structural engineer isn't onboard, how do you have a structural design certificate, that worth even the paper its written on? Have a structural engineer says YES, fill your boots, so to speak

No one could answer your questions without more information. Ideally your wall build-up drawings are needed, but you sound like you don't have the drawings down to a detailed enough spec, to even consider buying let alone building yet.

Would suspect it's down to the wall to window ratio and that will vary by room and by house. Example Our living room has nearly 30m2 of glazing and about 10m2 of external wall in total. So going for high performance 3G wins the day, every day. For clarity our living room has more heat loss than the rest of the house in total. So we upgraded to to 3G. I's all a balancing act something's make sense in one build and no sense in another. Generalising is choice decision.

So elaborate! Not exactly correct - the heating demand rate if 10W per m² max demand is a good indicator that us incorrect. That number being chosen for a specific reason - a heating element in the MVHR (flowing at passivhaus flow rates) can supply that heat without getting a burning dust smell from the ventilation air. A passivhaus still needs heat not much, but some, you don't need a huge gas or oil boiler though.

In Scotland mechanical ventilation become mandatory when airtightness gets better than 5m3/m2. So with a decent airtightness I would worry (like the other half) about piss poor ventilation. For the sake of a small cost in running install dMEV fans or a MEV system

So how does that work, if they are helping balance demand are they sucking energy out of the battery or is just by being installed its assumed that house demand will be next to zero in peak times? Without PV you generally as a residential customer, get nil for exports, unless on a one-off scheme for say a Tesla battery

£35 x 12 x 10 is £4200 so doesn't much in the scheme of things Web site says "Midway through the contract, you’ll have a choice: either continue with the monthly payments or pay a settlement fee based on the contract’s remaining value at that point" so it may be an expensive option? Only thoughts are - do they have the ability to suck your battery dry, at any time they want, so they get paid for export and you pay to charge the battery? Things that sound too good to true, normally are

Why? Our 6kW inverter runs both, obviously you can't run all the induction hob rings at once. Or just go GivEnergy AIO AC coupled, none of this EPS nonsense, it all works as normal in a power cut, that is the whole house electric carries on as normal, as well as the PV. So no change over switches needed the Gateway just does it all automatically. So much so you generally know nothing about power cuts that occur.

This is interesting, I recently switched from ASHP heating DHW to direct immersion, have I noticed a step change in running costs? - no. Our heat pump is fair distance from cylinder (a good 20 to 25m), it reports a CoP of over 3, but reality of kW of heat actually delivered to cylinder and the efficiency of a heating element in the water, means electric costs isn't much different, between heat pump and immersion. Immersion slightly more expensive, but not really noticeable. The other thing is PV, we get clipping (reduced output, even in February) of generation based on export limits, so using more electricity at midday is better than loosing it via clipping. Which with 3kW immersion is easy to manage with a simple timer. Cylinders there could be £6-700 difference in price between a direct and heat pump indirect cylinder - that buys a lot of electricity. On good tariff that's about 1.5 years of free DHW just on cylinder price.

A direct invented cylinder is about the 1/3 the price of an indirect cylinder. Time of use tariffs make it a viable option. Plus you could use a smaller cylinder charged to a higher temperature if you needed more capacity. So 300L v 400L. Not many years ago our 5 bed house had a 120L cylinder - how things change

But your cylinder average temperature most will not. My cylinder has the thermostat 1/3 up and it can read 7 degs, after a large draw off, but the water coming out of the cylinder is close to 50. So mean temp is quite a bit hotter.

We have a 6m overhang, but its the westerly afternoon sun in spring and autumn that gets in, can get really hot. Today sun all day solar gain from a low sun, so a benefit. So a cylinder with 3m2 coil as used by heat pumps, used with a gas boiler are great, either low flow temp or super fast reheat. Or you could do a cylinder heated by a heat pump, as in an all in one unit

In heat mode you get hot and stay hot until you open the windows. Your heat pump can only do heating or cooling, not both at the same time. You don't want to heat at night and cool in the afternoon, that's an expensive folly. Heat and cool is a seasonal thing not a day to day thing. You need separate thermostats for cooling, if the ones you have cannot be selected to cooling. You change the ASHP and the thermostats seasonally all to together. Any more helpful?

Our new build was completed with gas boiler, soon after moving in solar gains were painful. Bought a cheap ASHP to allow cooling via UFH. A year later the gas was disconnected, and ASHP used for heat and cool. Was cheaper then gas, no gas standing charges for one, using a time of use tariff, some solar and battery, makes ASHP as cheap as chips to use. I would drop down to 200mm centres and run from a single manifold (our floor area is 192m2 and we have 7 loops on 300mm centres). Run direct from a good boiler, so no pumps or mixers. UFH design, you need it room balanced by design, as far as possible, so room loops need to output room heat loss and each room receive its heat loss via the UFH. This makes balancing easy, I have all loops fully open at the flow meters and let the ASHP decide the flow it wants or needs. So operation can be two ways, WC or simply a fixed flow temp and a thermostat to limit, a single thermostat will do or a few, but don't bother with manifold actuators, so one thermostat needs heat all loops come on. Get an under floor wiring centres with some bells and whistles, so the room thermostats are actually temperature sensors and the can doo heat and cool, for when you install the heat pump. Boiler get a system boiler, not heat only one. Run PDHW (priority domestic hot water), this drive two temperatures from the boiler, one for heating the other for DHW heating. Get a heat pump cylinder, nothing else. Reheat times super quick and best boiler efficiency.

Think you should of asked the questions before you parted with the money. You really need an UFH controller that can heat or cool, this would reverse the logic of the thermostats. And reverse when the call call for heat or cool happens. Your heat pump should be switched between heat/cool, this can either be from the controller or a zero volt input is typical. Your whole system would have been simpler, no actuators, one proper thermostat or use the controller only as the better option. Condensation risk is managed by setting the correct flow temperature so 16-17 degs for floor. Floor sensors are way too late.

Maybe by area or post code?

For the cost of letting a company get on with it, there isn't much money to save by DIY, a lot of risk of fuc*ing up and getting an utter mess that isn't level, isn't flat etc. The other thing is the effort needed, self leveling or otherwise, to think to can do it yourself is a dream, it's a team effort, controlling people that haven't done many times before - life is too short. Couple of points here If the EPS is that fragile, the EPS design is not correct, if you need shuttering the EPS design isn't correct. You have already stated your no expert, so not sure your experience or lack of, is an added value here. Let the experts do the job, they are cheap for experts, build the walls yourself and save real money.

1st March export rates reduce to 12p/kWh, from 15p. So may need to flip to a different tariff for summer, such as Intelligent Octopus Flux

One day grants will go, they then become slightly better trained (or some will become) plumbers, looking for work like everyone else.

Well aren't you the negative one

So you can't use it then, you can ask the reason, but doesn't really change anything. What the fascination of SCC?

Possibly, but you need to go to your structural engineer to ensure it is of a suitable structural strength.

Go and read the bus grant rules for home owner and installer, then you will know what is or isn't acceptable first hand. Better than reading a load of second hand information - that could be 3rd or 4th hand. Always read source information for yourself.