Iceverge

Change that to medium blocks inside and outside and you get to 0.18. That's a nice calculator actually by Knauf. It is fairly optimistic with the values it's allowing for the airspace behind the plasterboard though but it'll get you through regs which I'm getting the impression is the aim. Hemelite blocks are a small bit cheaper too. Superglass is a bit cheaper again than Knauf. £51.37 inc VAT per m2 for the blocks and insulation.

I looked at earth tunnels when we built but came to the same conclusion as @Gone West. Minimal energy gain with the drawbacks of mould growth in the pipe and high install costs. As usual sitting down with a calculator and a biro very quickly dispells incompletely though out ideas. Passive stack was another. There's only 3 practical options really. 1.Trickle vents and extractor fans if you don't care about indoor air quality, noise, thermal comfort or energy use. 2. Humidity sensitive mechanical extract. Upgrade to humidity sensitive vents if possible. Good IAQ. Some energy loss. Minimal maintenance costs but some cold spots in the house. 3. MVHR. Excellent IAQ, minimal energy loss, best thermal comfort, no cold spots or noise. Higher maintenance costs may not be offset by lower ventilation losses.

But is very poor for airtightness. PIR boards are routinely installed terribly with lots of thermal bypass. There's plenty of threads on here to look at. For the same U value ........ a Wet plaster + double dense block + mineral wool batts will far outperform a Thermalite, PIR, Dot and Dab Wonderwall (don't sue me Oasis) As to the "lost" floor area just push the walls out by the same mm.

Pics please!

Regarding insulating insulated sheets aren't tremendously expensive. Even a minimal 25mm or so of Insulation would be worth it. If you really can't afford it or just want to stop condensation drips I would layer a run of chicken mesh over the purlines to support roofing felt and then use standard sheeting. There's a roof very almost level done on a stable here and it has never dipped.

Yikes...... Sounds like a recipe for a forever roof.Not in a good way unfortunately. What you have at the moment can be tackled systematically and safely. If you layer up new roof on old asbestos noone will want to come within a mile of it . If you take appropriate precautions you can remove the Asbestos yourself and get it disposed correctly. If you're able to take the time and care it'll save a lot vs a contractor.

That drawing seems to carry some magical thinking in a few areas . I'm really not certain what went on in this area. It doesn't fill me with confidence that your designers details were up to scratch. Do you have any specification as to what the builders were working to? Any pictures during construction? What is your specific objection to the work? Aesthetics or is it unsafe or leaking? What may help is if you have any wider drawings of the same area. Particularly sections.

There's a mistake here. I think I should have said 200mm cavity in the second example.

How "good" does this need to be? I'd be surprised if you couldn't wiggle something up into place. 50mm would be enough bearing. Maybe use 2 plys of longer bendier timber like 150*25 instead of a single 150*50. You could "truss" the roof by adding vertical support to the existing joists from the rafters.

Economic fabric first probably wouldn't be very nice to live in. It would only include the smallest windows necessary for fire escape purposes and they would be the lowest legally acceptable spec. For comfort I would always upgrade to thermally good windows before going behind Bregs insuation.

Good quality 3g white/white uPvc. Anything more expensive is just buying an Audi instead of a Skoda in my view. More $$$ without any more performance but at least the neighbours will be envious.

Standard dense blocks 7.5N is the norm in Ireland. Thermalites really add almost no insulation compared to making the cavity just a few mm wider. They're lighter to lift but crack easier and don't take wet plaster as well. Swings and roundabouts. 100mm dense blocks 175mm cavity batt 36 100mm Thermalite (0.18) will get you to 0.18W/m²K. Blocks and insulation~£65.14/m² If you used 100mm dense block 175mm cavity batt 36 100mm dense block ~£48.12 per m² You'd be at 0.174W/m²K

Yes sorry I was speaking in a general sence. Talk to the SE on this case. From further research and it might have some favourable qualities for a raft foundation. Flows well around complex reinforcement. Less heavy work with rakes and boots ducting the pour would mean less chance of damaging the UFH pipes.

Double the price. Intolerant of any small gaps in the shuttering. Can't pour it on slopes. That's my understanding of the down sides. Everything else seems better.

They do an option for Softwood stick builds too. Something like an 8*2 won't actually carry much more heat than an I joist. Espically if you add a cross battened insulated internal service cavity. Run it through uBakus to compare. Agreed fire is a concern. Would something like cereal fiber cement be an option? An layer of Rockwool Frontrock outside the OSB sheathing would protect from a fire in the cavity.