Nickfromwales

Use plywood cut down into a strip instead of natural timber. That won't split when you drive 2 screws in in very close proximity.

Still bewildered as to why anyone would remove all the service space within the posi-joists, but it's down to what each person sees is of value to them I suppose. Why showing no solar on the front roof? Architectural typo? With a swimming pool I'd be grabbing every ounce of 'free' energy tbh. Are you insulating outside the concrete core of the substructure and then again internally where the pool is?

All ICF systems hold the concrete core at 'arms length' with it being locked into the centre / core. "Thermal mass", as it has been nicknamed, would then exist in the floor and internal volume vs the fundamental walls themselves. It doesn't really matter tbh as all of the popular build systems typically end up clad internally in plasterboard, which actually has a very high 'heat capacity'. Thermal mass is this heat capacity, eg a surface or materials ability to absorb, retain, and transmit heat energy to assist in maintaining an equal / ambient temperature balance. I'd choose ICF over a TF with a PIR core any day as it offers a lot more decrement delay, but the hands-down winner ( IMHO ) is a cellulose blown frame. After being in so many of these in varying states, eg from start of build through to occupation, that's what I would choose for my own house ( when I finally finish doing this for 3rd party's and do my own build that is ). An ICF system could only really offer up its "thermal mass" if the concrete core was uninsulated internally and you wet ( plaster ) coated that for your finish, so this subject is utterly irrelevant afaic.

Bonjour, as we say in Wales. Welcome aboard. You'll be a welcome feather in the BH cap

Hi. If you want an optimum design for off-griddyness then I would suggest a dual cylinder arrangement. A 500L TS ( thermal store ) with 2x 3kW immersions, and a 300L UVC ( unvented hot water cylinder ) also with 2 immersions, with the TS preheating the cold feed to the UVC. This will massively increase your potential to store energy as heat, plus the TS can be depleted ( for heating ) without sapping all of your DHW for bathing. All excess electrical energy into the UVC first, then cascading to the TS. Batteries and PV can dump into either on demand, whichever needs a nudge. Another advantage is, if you have a diesel genny which is water-cooled you can divert the heated water from that into a low mounted coil in the TS to absorb every ounce of energy you create, wherever it gets created. When you have the least solar revenue it will be the winter, and you'll be needing heating, plus the batteries will need topping up via the genny, so, one problem gets solved and the bi-product ( wasted heat from the genny running ) helps to solve another by using even low grade heat at start up to the high grade heat after it's been running for a while. Zero is wasted. What are you doing in terms of heat emitter? Concrete slab with UFH to be used as a further energy store?

Anti-scald mitigation is a core safety remit, and BRegs requirement, so how do you tick that box with <46oC at the bath when turned to max hot temp?

Reference above to a conclusion drawn……was irrelevant as that chap was NOT off grid. Anyhoo.

ICF floors need a massive amount of support during, and a couple of weeks after the pour. Do you plan 1st floor UFH?

You buy a 22mm one and then replace the metric olive with a 3/4” olive @Russell griffiths would have known that if he wasn’t busy touching fish inappropriately. Or, just one of these ; https://www.screwfix.com/p/flomasta-compression-equal-couplers-22mm-2-pack/66818?_requestid=344691 with one of the olives changed out for one of these; https://www.bes.co.uk/3-4in-compression-olive-copper-21062/

Insulation is wise, wherever it goes. If EWI is laborious, adding the 30mm as I suggest is very simple and does not create any more detailing / work internally. Yes, you'll lose a fraction of internal room volume, but I would be confident this would be a cheaper and simpler route.

Just put 30mm of PIR internally on top of the studs, foamed to the factory-fitted PIR to prevent air gaps between the two layers, and use acoustic "sound barrier" plasterboard internally on all the external walls. That will stop the cold bridging from the studs, eg the connection from the outside layer of OSB to the room interior, and take you where you need to be. You'll need to live 2 more lifetimes to reap the benefit of adding EWI to this detail, so time to worry about something else now

Deffo, and will give a more spacious feeling to the room vs the solid panel imho.

IWI ( internal wall insulation ) is a great idea, and a vast improvement on the previous post!! 🙄 @Richvet, any update?

If anhydrite screed has been used, NOTHING will stick to it until the laitance has been mechanically "scrubbed" from the surface. At that point you will see the shiny semi-gloss finish reduced to a surface that looks a little like a pumice stone. That opens 'pores' in the screed which then allow such primers / adhesives / SLC's to be absorbed / key into the surface.........and then you're in business.

Actually, it wouldn't You'd just screw the sister stud to the left or right of each existing one, the same side all the way down the wall, and the OC's will stay the same. As per my earlier post to do just that. This is probably the quickest and more cost effective solution tbh.

To avoid hitting the straps. I always assume it'll be a semi-give-a-feck individual putting these up, so I make an allowance by providing 3rd parties with an 'idiot-proof' solution. For the window reveals you simply install the battens vertically against the straps, eg to the left of the left strap etc, and then just allow the PB to sail over the strap and form the edge. The PB fixed to the window reveal will come out to meet that and a scrim tape and skim ( corner ) bead will finish that off nicely. No need to apply the shaved batten to the strap, as the distance from the vertical batten to the reveal is negligible.

Yup. The solar revolution has begun, sadly. Prices are going up and soon it will get expensive. Problem is, the cheap equipment posse will be matching quotes from the big names and some folk will be sold a dream and get a nightmare.

You cannot do 10mm from the bath feed or you miss the whole point of the 10mm pipe Indeed, do the run to the basins ( hots ) in 10mm ( all of them ) plus the kitchen sink hot too. If you’re worried about flow, hook up a length and test run the kitchen tap before committing. I’d be shocked if you weren’t happy with the 10mm feeds, on the proviso that they all tee off minimum 15mm supply pipe. Done enough of these to speak from experience on live installs, so this is not a fag packet recommendation.

£10k is bloody heavy tbh. 4kWp fully fitted system from my solar guy ( SolarWatt German manufactured ) would be £8.5-9k absolute max if it were a pig of a job. That’s for glass/glass ( Vision 365 ) panels guaranteed for 30 years. Drop £1k to go to the foil backed classic panels with 20 years guarantee. For Chinese names the price should be lower.

https://www.screwfix.com/p/easydrive-bzp-bugle-head-fine-thread-uncollated-drywall-screws-3-5-x-25mm-1000-pack/25899?tc=ET2&ds_kid=92700048793290424&ds_rl=1249413&gclid=CjwKCAjwve2TBhByEiwAaktM1GXOfiYFdSyFp9XFuuRRjsdj-zinQmJEqVH9GYrZ4DeVNjcPCM1cuBoC0eQQAvD_BwE&gclsrc=aw.ds

Service battens affixed to every stud prob easiest. Maybe a sheet of 9mm OSB / ply cut into strips if you don't need to run cables down those walls? That's a proper PITA of a detail which the architect should have designed out IMO. 2x studs could have been sistered together for each rising strap, with the affected stud reduced by 6mm and its sister left flush for boarding. That's OK to do retrospectively tbh, so would be my favoured option here just to bring the wall forward to clear the straps and screws. Maybe consider horizontal 25x50mm battens at 400mm OC? A ball-ache any way you 'cut' it, as the shortest PB screw is 25mm.

Yes but you hadn't reduced the 4:1 figure which I would imagine is optimistic for heating via rads plus UFH, if keeping existing rads. 4 hours on Octopus? What will you do before that kicks in? If the system has already heated up via 'other' the HP will have very little to do, so deffo smaller HP going flat out imo. Noise for the neighbours may be a consideration, if you have any? Can you introduce a sizeable buffer tank? You could use those 4 hours to heat the system plus the volume of water in the buffer, then for the HP to shut off after the 4 hours expires. The heating would then consume the stored energy before needing to draw off oil again. If your home is very well insulated and has such low heat loss characteristics, then it sounds like this would ( could ) be a good option. Any HP will suffer short-cycling if the house performs very well and the heat demand is very low and steady ( eg after it has been initially brought up to 'comfort' temp ).

Do the hot feeds to the wash hand basins in 10mm. I do this on every job where running an HRC to an outlet is on the borderline of being overkill. Plenty of flow rate even with mains which are half of what you have there. Its just one more fitting each end, so an extra £10 per 'leg'. Chicken feed when you pay nearly £3 for a cup of coffee........

Pipeline Centre should carry stock. This is the best option here, but the OP would still have soldered joints to make at each end. @cwr, you could get a 6m length and have a commercial plumber form a mechanical bend at each end if this is really keeping you up at night. You seriously will be fine with a soldered joint. Any good plumber can solder this in their sleep.

Some manufacturers say the first 800mm - 1000mm in copper, in case the boiler overheats and sends super-high temp water out for a few seconds. Plastic pipe and fittings have very low pressure ratings at very high water temps.