ADLIan

Not so. Current version of BS does not use this number. It uses monthly weather data based on the building location

Condensation is often predicted with cavity walls. That’s the problem with taking the calculation at face value as in this instance any condensation risk is probably irrelevant.

This cavity slab from URSA available up to 175mm & 200mm.

Built in mineral wool slabs. 150mm now a standard thickness

The failure mode with this form of construction (render/insulation/sheathing(?)/timber frame) was well documented following failures many years ago in Canada. It was the same form of failure identified in the 2 houses I had dealings with last year. The information that I have to hand including Building Reg Approved Documents, warranty providers requirements, BRE and TRADA all show a render board (or other cladding) with ventilated airspace behind. @ProDave had an issue with similar construction but I'm not sure he ever got to the bottom of it. He chose the system as it had BBA Certification from the wood fibre manufacturer (not sure which). Strangely this Certificate was withdrawn shortly after he completed the work - I suspect because the 'system' was inherently unsafe! Without some form of 3rd party Certification/Assessment I doubt any BCO would accept the system. Sorry but this shows a lack of understanding of this particular problem. If your company is supplying product for this render system into the UK it must be suitable (robust, inherently safe etc) in all locations, from the bottom of Cornwall to the norther tip of Scotland and from east to west. Does your company undertake some form of 'assessment' to assess suitability for each project in its particular microclimate? Can you please explain how the product can be hydrophobic yet can still wick moisture away?

Do not render direct onto (any) insulation onto timber (or steel) frame construction!! It's not accepted good practice and lots of failures reported. About this time last year I was dealing with an architect looking at remedial works on this form of construction - sole plates and base of studs all rotted on 2 houses built approx 15 years ago. Does PUR really form a VCL if the board joints are not sealed/taped in any way? Moisture vapour is a gas so will readily move through the joints. Discuss.......

Congrats! From past experience. The mad/sad thing is no one from the planning dept will actually check on completion that you built your house to the upgraded spec!!! BCO won’t be interested either.

The EPC should give the air pressure test result - either ‘as measured’ in this house or based on site average value.

It's not a very good advert for an insulation manufacturer when they don't know the difference between a high and a low U-value!

Not just an energy statement. It’s imposing a condition that 20% of the CO2 target emission is from LZCT. From past experience it will never be checked.

Nothing to do with SAP - its a perfectly acceptable inclusion in the U-value calculation and is covered in the U-value conventions document that supports the Bldg Regs/Appr Docs. Done correctly, to MIs, mass air movement behind the plasterboard will not occur.

Aircrete block will generally give a much better psi-value than a medium or dense block (in the same detail). In a typical ground floor/wall junction expect the psi-value with dense block to be approx 3 times higher than with an aircrete block.

Yup. But check with your Building Control Body as it it responsible for enforcement

Vertical flashing and soakers looking at tile type?

This work would fall under the Building Reg requirements (assuming England) to upgrade the roof insulation. Generally max Uval of 0.18 W/m2K (IIRC) above conditioned space or max 0.35 W/m2K above non-conditioned space. Building Control needs to be involved.