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So you want a secondary inverter that has its export function disabled. I know that outback power systems products can stack in a master/space configuration, and they don’t export. That doesn’t help you though as you won’t be using their products. What you need is a battery charger, not an inverter. If you’re charging pylontech then look for an off-grid inverter that lacks pv input and talks the same can us as your batteries. Victron multiplus might be a good start.

If you can’t find a plumber to sign off your work (not many will) then you’re left with either the ignore option, or the ‘pay the local bc to inspect’ option.

One anti-freeze valve, on the lowest point, by the heat pump itself. Sell the other one on eBay. Ditch the fill/flush valve, they are chronically restrictive. I bought one then promptly put it in the scrap pile.

Report to gas safe, simple as... The scheme exists for a reason.

Looking at going out to the suppliers for windows and doors for the extension, going for 3g on the windows, but I'm struggling to find a supplier of 3g sliders in uPVC. Nothing massive, the opening in the blockwork is 1830mm. For some reason my supplier doesn't offer them, even though the profile is suitable. Anyone have a recommendation?

I've always been impressed with the offering from Burbage Custom (https://www.modernupvcwindows.co.uk), I'm surprised your experience varied so much from mine. I found the profile from Deceuninck to be decent.

My architect says that RICS are suggesting £3000+/m2 at the moment. No idea what we'll end up at with our rear extension, I've got the builders on time+materials at a reasonable day rate.

Well, hoping that the single story (pitched roof) rear extension that we’re cracking on with will reduce the exposure of the lower level to the sun. The extension is 150 cavity, full fill, thermalite inner skin. It will also have slab cooling. So that leaves the upstairs on the south aspect. New windows and a couple of fan-coil units? I guess it’s one of the downsides to a block/block build with solid internal walls. My timber framed shack in purbeck stays lovely and cool. Although it is freezing in winter.

At the moment there isn’t a plan…. Trickle vents, I guess. It will be a hard sell to go for anything electrically powered. Despite my wife watching an inordinate amount of TV, she hates electrically powered things. ‘Too modern, too complicated’ 🤦‍♂️

I guess we’ll find out when we replace the 2g with 3G on the south facing area of the house.

It turns out we’ve ended up with 240mm of PIR under the slab. That’s a result indeed. 100 and 140 cross laid (the 140 is left over from another job so we’ve only got to run the merchants for some 100mm. 40mm on the sides is the plan, as the pb and skirting will cover it

The open fireplaces are being replaced with a couple of wood burners, probably with external air supply into the floor void (my wife’s winning the stove argument, I’d rather take the chimney down)… would trickle vents still be the best option in this case?

Thanks for the input. Appreciate it.

We don’t have any vents in the house, or trickle vents in the current windows. We have two open fireplaces though…. I was assuming a dMEV in the wall of the extension? Is that not the correct place for it? There is an upstairs bathroom that had a north facing airbrick right through the wall that we plastered over years ago as it was blowing a gale through in the winter.

I put my hand on the inside pane of the downstairs windows yesterday afternoon, they were ‘quite hot’… so I’m assuming the issue is related to the glass as much as the walls. Hence my desire to go for 3G in the extension.

The west wall is the end wall. We’re about to start the ball rolling (slowly) on a double height side extension to replace that single skinned outhouse. But that might be 3yrs away, planning/financing/dno depending.

South facing walls, the whole ‘back ‘ of the house. There are four windows, all 1800x1200 (ish), all 10yr old upvc. downstairs is a kitchen and a sitting room. The front of the house (north facing just has a sitting room downstairs and the hall/stairs). House is painted white, roof is 300mm of insulation (with a bit of it compressed because the loft is boarded around the hatch). Now that it’s had a month of sunshine on it, it seems to be consistently stable at ‘hot’ temperatures internally.

The house in question: 1946 end of terrace, block + block, 50mm filled cavity (chopped and blown fibreglass) South facing, non shaded. The issue is that in summer, the constant solar gain on the southern aspect means that the walls are now a storage heater and it’s pretty nastily hot in there. Luckily I just leave and go to my rural property in Dorset which is sheltered and made of sticks. We’re up to dpc on a rear extension that will remove half of this aspect from the direct sun, moving the solar gain into the extension, which I’m hoping will be manageable through the better standard of construction. But apart from ewi, what are the options for managing the solar gain and subsequent heating of the remaining exposed wall section, the upstairs…. I’m going for 3G on the extension and will be changing the upstairs bedroom windows for 3G too.

dMEV = extract only? so the air comes in from the trickle vents and out through the extractor…

There’s the manual. It has a single call-for-heat dry contact that can go to a programmer, hi-limit stat or just a simple on/of switch. The main controller does everything else

Buy the right unit and the controllers are a piece of piss too…. The carel platform on the CE units really is fantastic in this regard.

Design it yourself, but the unit from Chris at CoolEnergy. Great product, great support. Find a local plumber, they’re easy as piss to install.

Appliancesdirect/aircondirect have completely sold out of the r290 based units until early 2024. Midea have an r290 based unit available in Europe but it isn’t available here. It seems that there is some regulatory issue preventing the mass adoption of r290 in the mini split market, which is a shame. They have been popular in china and India since 2013, according to the articles I’ve read. Anyway…. Still plenty of f-gas based ones available, if you fancy diy’ing…

Agreed, It was the first suggestion that loopcad spat out. I'll go with that then.

Something like this? 1-Drawing.PDF Or like this? 1-Drawing (easy-split).PDF