Nickfromwales

Would have been a copy / cut / paste document tbh.

Drill, hoover etc, and then fill the holes with CT1. Insert the plugs and push them home with the screw, then remove screw. Apply CT1 to wall channel, apply CT1 to where the channel will hit the tray, and then screw it on and wipe clean. All needs to be done in one sitting so you're 'wet CT1 hitting wet CT1' etc.

Yup. Excess will take the path of least resistance, so out of your front door and straight in through next doors.

So, is this a retro-fit? It’s a bit tricky to keep up with everything / everyone here tbh so remind me please.

Often wise, indeed, but also often restrictive, impractical and expensive. These are homes, to be lived in, vs some folk who seem to be enslaved to them to the point where I ask myself why they’ve designed it that way. The next rung down the ladder from PH certified is still an exceptionally good result, but, ( IMHO ), far more practical for ‘life’. PH lifestyle would probably better suit someone retired who could accept a 24/7/365 functionality. I’ve worked on PH+ levels of dwellings, and above, and these still needed ‘comfort considerations’ beyond what has been “suggested”. I’ve argued this out with ‘specialists’ and 9 out of 10 backed down when they had to put it into writing, and a lot of those have been successful by being behind the inherent ( assumed ) grandeur of a large, swanky, enterprise, and often that comes with a Stella price tag where clients feel comfortable because it’s “reassuringly expensive”. The industry is still in its infancy afaic, and PH / low energy / eco friendly etc gets thrown about by people who don’t fully grasp what these terms should actually translate into.

Done it plenty of times, just needs to be spotlessly clean and I rough it up with Emery cloth too. You don’t use glue for this, but instead use the proper ‘gap-filling cement’. Totally different beast.

More like for the 15 and 30 degree, plus “adjustable” bends Above ground fittings only typically come in 135 degree ( aka ‘45’s ) which is a PITA.

Sikaflex doesn’t clean off very well with baby wipes, but CT1 does. You just have to use them once or twice and discard, don’t try and get any ‘mileage’ out of them.

Yup. Do all of the drilling, and hoover out the dust, BEFORE you seal the tray. Otherwise all your hard work gets a nice coat of grit / dust over it and then you swear a LOT and go buy another 700 baby wipes.

I use it all the time on my projects, particularly the fittings, as there are many more variations available in the UG ( under ground ) range.

That post deserves a reply where I haven't drunk 4 Brewdog Punk IPA's, so bear with. It's not my fault, they made it very drinkable.

Yes, odd indeed. I don't really see this being viable in a residential setting, but maybe more for an industrial-look dwelling, actually it would be ideal. Condensation would be my worry, as heat rises to where these reside, and the two would ( surely ) be scrapping it out constantly? It denotes 21oC temp on "surfaces" but fails to point out that your head is also going to be one of those surfaces.

On what type of subfloor? If this is a passive / insulated ( well-insulated ) raft, then it would never be "cold" ergo you'd never need the upper 'mat' to be more than 50-100W mw2 tbh as it would have just so little to actually do. This is said whilst assuming that if the UTH ( under tile heating ) was needed, then it would be a winter period where the UFH ( regardless of type ) would at least be loitering around and effectively warming the slab to an acceptable ambient. Electric UFH in slab with a proper ( thicker dia ) "in-screed" heater wire will heat perfectly well, with zero hot-spots. It'll be installed low enough in the slab to not be able to be 'a thing'. I've done enough to know. First random kit I found for an example I am 1000% on board with your plan, and have done wet UFH + Willis heaters for a number of clients which worked very well indeed and was KISS all the way, but the wire is KISS+, with absolutely zero maintenance. The ONLY thing I don't like is the possibility of it breaking down, which, unfortunately heater wires do, frequently. Wet UFH is a lifetime system guaranteed, as in if it's leak-free from day one, it'll be a safe bet that it will be likewise 30 years or more onwards. So, your estimate of £350 for all that area to be populated with a robust electric UFH in-screed wire is nonsense, sorry, so not a realistic budget at all. That makes wet UFH more viable AFAIC, so I'd do the maths again, properly, and reconsider. You can use a basic or complex resistive heating source vs an ASHP if you wish, but I'd just need SOOOO much convincing no to treat myself to a cool slab in summer that I doubt anyone could ever sway me. Very well insulated and very airtight dwellings are just almost incomprehensively comfortable to be in, it's just mind-boggling. Just a pinch of heat in the slab, and a few bits of strategic comfort heating here and there is all you will ever need.

It's commercial only, is it not?

It makes perfect sense, it's probably just your not thinking straight because your brain has become a bit 'squishy' from sitting in your house at 23oC A basic PHPP analysis does that, but you can then opt to go for a room-by-room analysis which has proven many PH designers are wrong and has seen me walk away from a few projects where the client has favoured their architects opinion over my experiences / knowledge I fortified by what I generally already know what the PHPP analysis would show ), particularly when I challenge PH designers over room temps at different ends ( South to North ) and the 2oC swings that come with that consideration. One big name ventilation company had no choice other than to ( eventually ) admit that 2 bedrooms upstairs would need 500W electrical post heaters embedded in the ceilings to get those two rooms up to 20oC with no other heating up there, and no UFH downstairs. No two builds are the same, that's a fact, and when someone shows me a true PH design I always look at it and squint a little, as they're just way too optimistic IMHO and are typically formatted on an 'immaculate' scenario with the occupants held hostage within. Your turn

Still a nope, sorry. Defo not the case at all. A good PV diversion controller will dump 100w and upwards into the immersion, so not even 1% indiscriminate. Every single drop of excess is grabbed and pointed at the dump load, so, dumb, it is NOT. Which means for the same size cylinder they will need to run for longer, requiring much longer / sustained periods of 'excess'. A kW is a kW, regardless of how you get there. It may be past my bedtime, but, "WHAT!?". So, solar PV, bought and fitted, it's producing excess energy beyond your consumption, and you'd not use it, WHY? Reducing countrywide consumption by each adopter of PV utilising as close to 100% of it as they can will drive down fossil fuel consumption at grid generation locations. I'm lost here, sorry.

Best time you'll spend, as the floor will only be as good as the deck it sits on.

Normal plywood. Tanking with a liquid tanking solution or membrane ( if you're rich ) in known wet / splash areas is a no-brainer, so sense always prevails. I've used Ditra etc where it's been a dodgy screed ( laid by other and I've not laid it ) and brilliant results. I've only ever used Ditra once over chipboard, and that was in communal flats where the chipboard floors were all non-mechanically fixed ( zero screws whatsoever ) for acoustic control. Every single other job has been plywood, without a second thought.

Good luck monitoring and facilitating that!!! By the time the suns out and the excess is generated, and the HP switches on, and then gets up to premium temp, and is then up and running long enough to be heating DHW effectively, the sun and any "excess" ( aka the requisite surplus thereafter base loads are satisfied ) will have disappeared, and the whole lot will have switched off again. The HP and ancillary equipment will take a battering with this setup. Excess to immersion is the better choice AFAIC, and zero moving parts, zero LAG, and nigh-on 100% proportional ( so anything after 100W gets used by the immersion ) whereas those pockets of excess would NOT provoke the ASHP to fire at all. Add to this the extended longevity of the heatpump from NOT doing such a crazy duty cycle, christ knows how many times a day, and it's just not a great idea IMHO. Nope.👎

I doubt you'll have enough solar during the winter to provide space heating tbh. A2A A/C ( which will heat in winter and provide cooling in summer ) would be my choice. Very cheap to run, and only about £2k to buy for a reputable make, but you can get much cheaper.

£1500 is the price of a decent MVHR unit !? Let alone a whole installed system. The requirement for MVHR is not a choice, it is mandated by the number of air changes per hour demonstrated by your blower test result. Have you had one done?

You'll want 5 screws per chipboard deck, per joist, minimum. If not, add more before ply'ing.

I've NEVER once used backer-board when tiling over timber floors, ever. Never had a single crack / failure / issue and I've been tiling for north of 25 years. Plywood, glued and screwed, is absolutely bombproof AFAIC, and I actually dislike backer board because it doesn't conform to undulations like plywood does. If the sub-floor is "wonky" you also have to set the backer-board down into flexible tile adhesive, and screw it, so I'm not a fan. 6mm ply or even 4mm will suffice, and I only ever use thicker if I'm trying to match adjoining floor thresholds etc.

Email building control and ask for a breakdown of their responsibilities, and also contact the Citizens Advice Bureau as they can offer free impartial, honest ( sometimes brutally honest ) advice to you so that you do not trip yourself up during this process. I doubt they would become pedantic about anything else as that would see them leaping onto their own sword ( as why didn't they identify that during a previous visit ? ). I'd just ask the cowboy builder to supply all the materials for the re-build, and say that's all you want from them and they can leave without any further responsibilities, as, to be frank, this is now just about damage ( cost ) limitation and pretty much nothing else. The builder may already have a CCJ, so won't give two hoots about getting another.

You have WAY too much spare time on your hands! PMSL.