Andehh

Install a slit drain/narrow drain, and tile either side? Bit like what we did with a semi flush patio.

Wow, that post reminded me of times gone by! Yes... That loneliness was so heavy at times. Exactly as you put it. We're approaching 2 years since move in, and 6 months since 'finished', and I still very regularly look back through photos of the harrowing times we went through "alone" a... But boy I have I learnt even the deepest of wounds heal, and it's amazing what you look back on and laugh..... Deeper the shit, the funnier the story you eventually tell.

Looking back, this is one change I would have liked to have explored... Incorporating external blinds into our build. However, as much as I like the idea of them.... The maintenance and risk of something going wrong I think would have meant we would have needed to opt out. There'dhave been a dozen blinds required for us... Each one with so many moving parts, outside, with wind, damp, and change of temperatures.... And any failure requiring such extensive damage to window surrounds, which would never be seemless to replace (if change in mortar colour, tender patch job) etc. You'd need to try and incorporate some form of access hatch IMO. Maybe try and make an aesthetic/styling thing to disguise the access hatch? You've gotta really really want them to roll those dice!

Yep, we hardwired all our blinds... No regrets! Just need to tidy it up a bit.... 2 core all that was required. Even if rechargeable is easier having several blinds would quickly be annoying!

Low carbon argument also stretches to building it to last, and preventing a need to repair and replace!!.. The most sustainable wall, is one that lasts a very very long time.

As said above, I would guess that cold air is blowing down the gaps/tunnels moving the warmth out. Trying to go around the edge of the room and use expanding foam to deal the end of each of those tunnels would be a good first step to try I think!

Clean as deep as you can with builders wipes, let it dry then Ct1 or equivalent, slightly warmed and pushed in deep! Smooth to finish.

That looks suspicious to me,

We have similar, but only realised it part way through fitting. So we've got a property we worked hard on getting a reasonable air tightness....then stuck a great big Stovax dual sided stove in it with the air inlet kit creating a 4" direct feed sat underneath it. Live and learn The stoves worth it though, even if we live with a knock to the air tightness, and despite wibbling about it for ages... I have NEVER noticed a draft around it, even on windy days. And with our total energy bills averaging out at about £150/month for a very large and sprawling bungalow, with very heavy usage and a large background drain, (server, CCTV, full networking setup, dehumidify in garage etc) ... I'm delighted all round!

Have you looked at YouTube for possible solutions for leak tracking like this? Otherwise a very hot day, try and let everything warm up, then cold cold water and a thermal camera?? Random idea!

I'm not ashamed to say I watched that twice, that shits cool.

Yeah, it isn't foolproof and has caught me out as well before! Have a look at a few YouTube videos before you use it.

So they have a cap they installed 3m deep, somehow by digging and literally putting a 700mm slab on top of it? Then an additional one done at surface level... Or do they back full in top of it? Very interesting!

Got the MVHR in boost atm to refresh the air inside as I get into bed, prob about 10% as effective as our actual AC units. If you want swift and effective cooling, you can't beat a proper AC Unit. Duct it through the window and accept it isn't perfect, but it is effective.

Was it driven or used as a driveway before the concrete at all?