Redbeard

I thought it would look pretty naff but I did some over a dodgy concrete floor for a relative and it looked fine.

Thanks for the links. You are right re 'flexible'. 'Soft' (ish) yes, 'squidgy' (a bit), but not flexible. I have had a look at the links and we all seem to be describing the same thing; a 'soft-ish but rigid-ish' insulation board often (but not always, bonded to plasterboard or MgO board. Very expensive and unpleasant to handle due to its powerful dessicant effect. In your links I see that the claimed lambda value of at least one variant has increased further to 0.016W/mK

Have you got any links? I cannot find anything that is other than an aerogel/Spacetherm blanket stuck to a board - whether Magnesium Oxide or Plasterboard. I was loosely involved with the planning of a refurb in 2009/10. The contractors hated the pl'bd/aerogel laminate (a) for being so dusty and (b) as the mesh in which the aerogel was held 'picked up' when drilling for fixings, potentially hurting wrists or sending operatives spinning!

Agreed. When Proctors started marketing it the stated lambda was 0.013.Over time it changed to 0.014 and then to 0.015W/mK, where I think it stands now. PIR 0.022 (some say 0.021) and phenolic 0.020 (some say 0.019). I have not looked at the price diff for some years but it used to be v considerable. Looks like 14mm of PIR will equate. I know you cannot get 14mm, but Celotex used to make 12mm. One source says they no longer make it and others say they do. One source refers to Xtratherm's 15mm board. I used to buy 2 sheets of 12mm at a time and the carriage exceeded the material cost!

Sorry, my previous post relates to @ProDave's sugg'n of a Bldg Notice. I too remember when you could do major works, or even a new-bld IIRC, on BN.

AI says that Sheffield City Council says: "You can only use this for minor domestic jobs. You must use a Full Plans application instead if your project is near a shared public sewer or affects a commercial building. [1, 2]". Maybe it's the drain.

Re my earlier post (yesterday) and Principal Designer role I have found the thread with @flanagaj's query:

The architect's quote includes but does not seem to include the Bldg Regs/Bldg Safety Act Principal Designer role. So you or your contractor could end up being deemed to be the PD. See @flanagaj's recent topic re the same issue. Edit: Cannot find @flanagaj's topic, though I think it came up earlier today.

Yes, 'tightening' the envelope makes sense, but we cannot comment too much further on the walls (and floors) till we have more details. Are the walls cavity walls? Are they already insulated? If not, while a 'base case' U value of 1.5W/m2K is not quite as bad as a 225mm solid brick wall at 1.7, it is not exciting, when 50mm of insulation can cut heat loss through much of the walls to a third of that.

Re: IR camera: Yes. Re: Living in it... Seriously, sheet/seal off each room as you work on it and (it being a bungalow) access each room externally. I would use DPM (Clear if you want to save on elec for lighting!) and good-quality 'Gaffa' tape. Probably don't be tempted to use air-tightness tape as you'll struggle to get it off. Remember to seal also any entries/exits such as pipe and wiring runs. If I were doing it again I would have a basic shower 'room' (shed??) so that I did not bring filth back into the clean areas. (Probably requires more discipline than I have, though!).

Yes. Several stand-alone TF builds and extensions in last 18 yrs. None of them used treated timber. I take the view that if you design out as far as possible the pre-conditions for rot then using timber treated to resist rot is a bit over-kill. It seems to have worked for me so far. No Qs ever raised by BCO.

OK, thanks for confirmation. I do not know how much you know about IWI. Is the house cavity walled? If so, get a quote for bonded polystyrene beads (usually subj to min 50mm cavity and no cr*p in it, and other caveats). I would then get someone to do a WUFI (dynamic interstitial condensation -IC- risk analysis) calc to see how much IWI (if any) you could add without falling foul of IC risk. If it is 50mm cavity, un-filled, existing U value will be circa 1.5W/m2K. With poly bead fill, circa 0.45-0.5, and with 50mm rigid wood-fibre IWI approx 0.3W/m2K (again, importantly, subject to a condensation risk analysis)

Welcome. Think about air-tightness (henceforth A/T) and high-standard insulation as the 1st thing you do, and then worry about the rest (unless doing the insulation would preclude structural work!). I assume 1950s = clear-ish 50mm-ish cavity (the general assumption being that 20's/30s+ = cavity) but, for example no-one told the builders of entire estates in Nottingham that! So inspect; don't assume). Either way, seriously consider external wall insulation (henceforth EWI) rather than internal insulation of the external walls (IWI). *Design* your elecs and pipe runs so that they don't make insulation and A/T difficult. And most of all, have fun!!

It's not just about points 3 and 4, but if you can cover the points below you could be OK. I have been my own PD. https://www.castlepoint.gov.uk/documents/d/guest/guide-to-dutyholders-designer says: Competence: To satisfy the requirements and carry out any design work as the designer or principal designer, a person or organisation must: - − have the relevant skills, knowledge, experience and behaviours necessary to undertake the function. − carry out the design work in accordance with all relevant requirements. − provide adequate supervision to those in training within the design role whilst carrying out the work and ensure that those under supervision are not appointed as principal designers. − consider that an individual wishing to designate themselves as a principal designer within an organisation must take all reasonable steps to satisfy themself that they have the skills, knowledge, experience and behaviours necessary to manage the function of principal designer.

Yep, tackle 100% of the floor in 40, 40 and 20% tranches and you may have cracked it! But don't quote me! My justification for spending more than I probably have to on Bldg Notices is to avoid the situation on a subsequent sale where a buyer's solicitor queries BC approval for specific works. If the answer is, or suggests that, that you don't have it they express 'outrage', which can be instantly dispensed with if you drop the price by £x000. I will have in my hand a sheaf of BC approvals and stand my ground.