Redbeard

'Mineral Wool' is usually used as a 'cover-all' term for either Rockwool (or rockwool!) or glass-fibre. I don't like working with either of them so tend to avoid them, but if they don't bother you, use what you can find cheapest. (Note that rockwool is available with a range of lambda values. 0.044W/mK is 'standard'-ish, but I think you can get it down to 0.035 or even lower for rigid or semi-rigid batts (the EWI stuff for example tends to be around 0.034, but you would not use (nor want to pay for) that in your roof void.

If it's 'blown' (the seals on the separator bars between the panes have failed) there will be condensation inside the units, between the panes. If not, they're OK. It is very hard (without a special detector) to establish whether a unit has low emissivity glass to at least one pane, but if you can find the date of the windows you may be able to 'reverse engineer' with ref to the Bldg Regs at the time.

Crudely, as long as you can see through it the insulation value is not that good. A really good triple-glazed window may get you a whole-unit U value (i.e. everything; not just the glazed unit) of as low as 0.7W/m2K. Assuming your cavity has no fill and is 'typical' for 1975 (circa 50mm) you'd get 0.55W/m2K or a little below with blown-in insulation. (I'd recommend graphite expanded polystyrene, not mineral wool). Your area of wall will (unless your house is very atypical) be far greater than your glazed area, so the right order is walls 1st, windows and doors later (unless your roof insulation is the original (?circa 50mm) in which case carefully lay 300mm on top: U value around 0.14-0.15W/m2K, and do that before everything else). What you do with doors and windows also depends on the state of the whole units. If the frames are not original they may have a reasonable standard of draught-stripping, in which case your main 'let-down' is the glazing spec, and when it comes to glazing compared to other fabric elements it's a question of 'less bad' more than 'better' (The 'holes in the fabric' will always fare worse than most other thermal elements even with 'bells and whistles').

How about rigid EWI which you can fix to the concrete and then render over?

The lead under the tiles is (are) the soakers, AFAICS, laid as you'd expect as per the slates (I think). There is then a sort of 'mini-skirt' flashing over the upturned soakers, again, as far as I can see. Although the abutment is different that's how the soakers work on my extension abutting the main house wall with ridge at 90 degrees to the main house wall. My 'cloaking' (over the soaker upstand) is different in that it's a thinned-out layer of EWI, and comes down further, but the principle is the same. The practice is different in that mine does not leak... Looking at it again we used to allow a 150 upstand for soakers and stepped flashings and bottom and top 'aprons'. Do we think rain could be 'bouncing' over the lead-line, soaking into the sand/cement 'fillet' and running down? (Not certain I buy that even though it's my suggestion, but 'discuss'!).

Is the stack within the thickness of the party wall? I can't see a 'chimney breast'. Can we have external pics? How does the purlin socket line up with the edge of the stack, for example? Can we assume it is about on the bottom side of the stack? If so, in the absence of any other 'hypotheses' so far, can I throw in porous stone effectively 'by-passing' the flashings and soakers? Have *you* had the roof re-done or was it like that when you bought the house? Did you have exactly this same problem before you had the pointing, flashings and soakers done? A bit unlikely, but could water be getting (in some volume) *inside* the stack, soaking the wall and transferring through. I assume you had the flaunching done at the same time as the other works?

+1 Can I guess that you have already been quoted an approximate 'price point'?

Phew!

How am I going to listen to The Archers then??!! 😉

What did your plans say about the Warm Roof build-up and about insulation and fire-proofing of the steels? Got any pics so we get more 'context'?

Is the house newly-completed? I knew someone who was very worried about their 'thermally-broken' alu windows in their new-build suffering from considerable condensation. However, once the plasterwork had dried out the condensation stopped occurring. I was not there at the time so I cannot comment on the actual frame temperature. I am not convinced that your humidity is excessive. I too am concerned that there is no isolation between frame and masonry, but tell us more about your house. Is it new or old? Is the frame connection to the inner or outer skin if it's a cavity wall? If it's not a new house but *is* a cavity wall, fixing to an un-insulated cavity closer (probably a brick) could, I think/wonder, effectively 'by-pass' the thermal break.

Power-Pipe UK | Waste Water Heat Recovery Systems A Power-Pipe® recovers the heat energy lost down the drain during showering and uses it to pre-heat incoming mains freshwater. Saving £ + energy. No, I didn't know either!

I took 'bare walls' as meaning that the walls were stripped back, whereas in fact 25mm is pretty thin, but as your experience shows it is on the 'steep bit of the curve' in terms of insulation efficiency. Nevertheless, since you do not have what I thought was a 'blank canvas' (to 'engineer' a lay-up with both insulation and support) I suspect the answer is to fix battens for the units through the insulated plasterboard, doing your best to make good the VCL which you puncture (a 'liquid grommet' of silicone is the best I can suggest, or small 'tabs' of EPDM or butyl tape) and then make sure your screws through the back of the units go no further than batten depth + plasterboard depth. If your insulation were much thicker I would be worried about torsional stress on the screws but 25mm is pretty minimal. Edit: Just realised this is still in the 'introduce yourself' section. OP, you may want to see if the moderators can move it to the correct section, where it will be more accessible for others searching re similar issues in future.

Is the kitchen below? Can you drop the shower waste down and take it out at GF ceiling level, or even GF level?

I think the only 'perk' would be that if he did go self-employed in future there is a small income tax offset allowed for use of home as office. I think the top rate (it's based on how many hours you use it) is £312 p.a.

we----ll... It depends whether you follow the school of thought which says that a hole with a screw in it is not a hole. If you share my pessimism (that it might be; a bit) you could fix through little squares on EPDM or butyl tape which sort of 'self-heal' around the screw more than membrane does.

Crazy thought but... ?Bubble-wrap?!!

Splendid user name!

Could it be that (though Victorian) the bay is of cavity construction? I wonder if potentially that air-brick is venting a cavity and at the bottom of the hole (under the stone plinth) is the air-brick which should be venting the floor void. (Not sure how that works with the proximity of that drain, though).

Mineral wool: Worse lambda value - completely non-combustible. EPS: Better lambda value - combustible but protected by render layer. If you don't like using plastics go for RW. Note that you would not use RW down within the splash-up zone. That would be High Density EPS or XPS. I have never seen PIR suggested as a 'below DPC' plinth layer, and certainly would not choose it myself. PIR is not generally used for EWI, to my knowledge.

Without moles.

Agree, we need pictures of the curves. If you really need to follow a curve then (a) it depends on the radius and (b) while plasterboard can be persuaded to follow a curve, insulated plasterboard would need slots cutting out of the insulation, making efficacy and continuity a bit iffy. Flexi-something followed by something like Intello membrane and 'steamed' plasterboard. As far as If you are concerned re over-enthusiastic 'stuffing', staple some breather membrane between each rafter pair, 50mm from the felt. Stretch as tight as you can and then you can 'stuff' with abandon. How about using 'Larsen Trusses' ('poor persons' I-beams')? Basically a sub-rafter hanging below the existing (parallel or at 90 degrees). The latter would help if you really need to achieve a smooth curve.

Re video: Strewth! That's more flex than I have ever seen, but it is bigger than any single pane of mine. I can see why you are concerned!

Well it depends on whether you take your view or theirs. Yours, I think, is that although you took all the walls down (the front one having nearly fallen down, I accept) this is not a rebuild. Theirs seems to be that, since they were able to take pics of a cleared site, it obviously is. If it is, it needs to comply fully with new-build Building Regs and Planning requirements. That would, for example, one assumes, include all-new foundations. You do not mention foundations, but I think the suggestion is that the walls have been rebuilt on the existing ones, which may not (or may) be deemed sufficient.

Re getting a letter of support from BCO, I have no idea whether the Planners would take this into account but it cannot do any harm. At this stage you need all the offers of help you can get.