JohnMo

2 approaches really to install and control. Lots of zones and buffer, or 1 zone then no need for buffer. In all cases you really need to run on weather compensation to get the best efficiency. The approach taken depends a lot on how you live in the 24/7, or out at work for 12 hrs. If the later radiators may be better than UFH due to response time. Basically you need low flow temps to heating and for DHW a cylinder with a big heating coil (3m2). UFH design is another topic really. Download the Grant manual, that will tell you exactly how it will be installed. Pipe sizes depend on circulation rate required, for the ASHP, pipe lengths and bends and the resulting pressure drop. It's sized to suit each install (or should be).

I look at CO2, which basically manitory in Scotland unless your house is declared to leak like sieve, for the master bedroom. I installed a duplicate in the lounge also. They are mains wired, gives instantaneous CO2 ppm, average over 8 hrs, 24 hrs and peak over 24 hrs. Mine is made by Deta.

Buy self drilling screws?

Max size in what respect? Can be as big as want, doesn't mean it complies with any planning rules.

For best price search the internet and chat to local suppliers. Price vary almost daily. Mine came from insulation hub and it came on lorry direct from the factory. I think I had about 400m2 of 100mm. Priced recently for another project and they weren't the cheapest, but as said prices vary. 100mm isn't much below UFH!

I've never found a good sander, always seem pretty rubbish. I find a good scraper is way better, then just use the sander for finishing off.

Vastly under estimated time required every time. Never order enough materials, so alway one or two more trip to get parts. But always finish the jobs eventually.

How are you running the heat pump For UFH what is your flow temp and heating regime. How many zone and how are operating? Same for DHW ?

Willis - Have a look on eBay, you can just buy the casing, so you can fit any elements you want.

All you need is a Willis heater. It's an immersion designed to add on to cylinders that don't have immersion, ties into the inlet and outlet piping. Have search on Google (or other search engine)

I'll start off Durisol Advantages 1. Easy to DIY, just read the installer manual and/or go on the course. I did mine at the height of COVID, so no training available. No issues I just read the manual. If you one of those that knows better than reading a manual, the product is not for you. 2. Pretty good U value out of the box 0.14, for the 365mm thick block. 3. No special tools or props, or support system required, except adjustable props at the opening (ease and cheap hire locally) 4. Vapour open breathable walls, remains so with a cement/lime parge coat, while becoming airtight. 5. Little or no thermal bridges 6. Can build in just about any weather and pour concrete at just about UK temperature - well in the minus temperatures. 7. Didn't that much rebar, when compared to other systems. Disadvantages 1. Not air tight so a large coat or similar required internally. 2. Blocks are not fully square due the the tapers in the moulds. Once you realise it's easy to make allowances. 3. Only 6 rows of blocks high between concrete pours Some say during the build the house will get flooded as the they are open to water entry - our build started November and windows weren't in until April, we had no issue with water getting in after the roof was on. We also had 2 walls open and not covered externally for approx 2 years with no issue.

Yes at each corner, above and to side of each opening and in middle of rear wall. Your structural engineer needs to design the rebar. Every build is different. Loads of rebar in foundation also.

The pump in the heat pump will do that, when you plumb the buffer as a 2 port. Having two pumps in the primary circuit you actually start getting into hydraulic issues, as the pump in the heat pump wants to modulate to manage Diff Temp, the other pump makes the control of the two pumps very erratic. If you have pumps on the UFH manifolds these will pull water through the mixing valve, the hydraulic sepereration is then across the mixing valve. The biggest difference between a 4 port buffer and 2 port is the hydraulic sepereration. A 4 port gives you a primary circuit - ASHP to buffer and secondary - buffer to rest of heating system. You need a pump in each circuit. Piping as a 2 port does not give hydraulic sepereration the buffer just becomes heating volume. The ASHP to heating system is all primary circuit. I just have my whole UFH system either on or off, no actuators on the manifold. A single thermostat which, either has the ASHP on or off. All run off the circulation pump in the heat pump, also have no buffer.

A mist coat is watered down emulsion. Take emulsion add 20% water mix well, paint/roll as you normally would. Next coat full strength emulsion.

Following out of interest, I take you want to keep your existing inverter or are you planning to replace for a hybrid inverter?

Just shows the benefits of self install, save money in the first place on initial install, then a few years later you are in profit. Even in the north of Scotland. Out of interest had a quick look at my export, since my new meter was installed last year I have exported 131kWh, the previous meter was at about 36kWh. So 170kWh in a couple of years. Generation stands at just about 3000kWh The excessive export is mostly due to the immersion diverter failing. Mine also is a self install so get no export payments. Certainly don't regret the none MCS install.

Water down normal emulsion about 20 to 25% for first coat, same with all plasterboard.

Have you installed the top level UFH piping?

On a smaller buffer, you get plenty of mixing between the flow and return which requires the heat pump to put slightly hotter water to compensate, so there is a cop hit with the four port plumbing. You also need an extra pump on the secondary side. You do not need a bypass with this arrangement as the buffer acts as one. The two port plumbing of buffer, mixing doesn't matter as there is no interaction between flow and return, so you may get better CoP. A bypass valve may be required, depending on how you arrange your zones. You don't need a secondary circulation pump as the circuit is now all primary. The buffer becomes a volumiser. Generally you are going to a lot of pumps running all the time if you are not careful with the design. At the moment you have ashp circ pump, secondary circuit pump, one pump per UFH manifold. On a 6 month heating season, that could be £200 running costs just for the circulation pumps.

So only guessing here. It could be it's learning and (really a bit of question) could it be struggling to reheat the 10 degree drop in one heating attempt? So it's starting to heat earlier. Heating to 55 isn't that good for CoP, a lot on here, heat to about 47-48, the you can set the hysterisis at 2 or 3 and heat pump has way less to do.

The best place to buy is eBay, they come up quite often, usually for a good price. Here is a manual, just replace boiler with electric inline heater. New FlowSmart Inst and serv instructions 2-12.pdf

PIR is a pain to install well, very easy to install badly between joists. So not sure I would go there. We added counter battens to increase depth to 350mm then did full fill with spray foam, Then double taped avcl over the whole lot, and glued to the walls. then 50mm battens and plasterboard. If you don't like that idea, go with something like Frametherm 32 between the joists, the underdraw with PIR etc. Whatever you do make sure water vapour cannot makes its way in there.

A slight left of field suggestion Very small cylinder say 50l. Heat to around 60 degrees via heat pump - cop of 2. Or via immersion and solar. Not a big cylinder with an outside diameter of 450mm dia and 600mm high. A cylinder such as an Alpha Flowsmart 50 has a DHW coil inside and has heating system water inside the cylinder. Have a thermostatic valve on the outlet of the DHW coil and set to about 30 degrees. This would then provide loads of preheated water to an inline electric heater. The lower heating requirements of decreased delta across the inline heater (no longer with an 8 deg inlet temp) will give a considerable flow increase or allow a smaller kW input for the same flow.

Fresh-R is one, but you can do it with a normal MVHR unit also. You could use something like a PIV supply nozzle connected to a standard MVHR as a single supply point. With extracts in wet rooms and where required transfer fans. The other thing to look at is coanda terminals, for supply and extract. They work by the velocity of the air sticking to a surface (ceilings), so you can have a supply one side of a room (even at a doorway or air exit point), air coming out of the nozzle will travel approx 4-6m then come down, travel back across the room, down the corridor to the nearest extract point. The air when it comes down is at room temperature, the air stream is wide so velocity is low, no draft. I have them in lounge and all bedrooms, duct lengths are shorter compared to a normal nozzle.

Really - you have put 2 years into it and now you want to knock it down and build from scratch. By the time you get planning and built another 2 years, if you get contractors in, 3 or more if you do lots yourself. How much heating energy do you think you will save to recover costs. So build cost £2k/m2, 100m2, is £200k to build, save £1k a year on heating (which you won't)- 200 years pay back. Get some decent contractors in and get it done. Money obviously not an issue, or you wouldn't be posting the question. Or is getting a passivhaus badge the important bit?