ADLIan

Please do not omit the fixing(s) - it's only one or 2 per board (check MIs). In a fire any plastic insulation attached to the plasterboard will melt or soften and the plasterboard may fall off the wall. This exposes more fuel to a fire (combustible insulation) and blocks possible escape routes. Additionally it could be a major hazard for fire fighters if they have to enter the building if people reported in there.

I believe approved contractors (to PAS????) can self certify

I’m sure PUR is ok for with render. Does this product have a foil face? This may be the problem as render will not stick, product for direct render normally has a glass tissue facing

Ask him what part of Approved Doc H (assuming England) applies. New one to me.

The BS that covers the calculation of ground floor U-values includes an assessment of the sub floor ventilation in suspended floors

For floors with the same footprint, edge conditions and say 50mm of PUR the solid floor will offer a slightly better U-value, but perhaps only by 0.01 W/m2K, compared to B&B suspended floor. With 150mm+ of PUR there's even less of a difference - unless you start looking at the 3rd decimal place or beyond.

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 Strangely this Certificate was withdrawn shortly after he completed the work - I suspect because the 'system' was inherently unsafe!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.

Doesn’t read well when they knock the competition, by name/type so much.

It's all in Appr Doc F in England. Do you currently have background (trickle) vents and intermittent extract fans to 'wet' rooms? If your air pressure test comes in at less than 3 you will need to upgrade this to continuous extract or a mech vent system. Get the test done and see what the result is. If you get less than 3 I am sure there 'ways' of increasing this to above 3 (open a trickle vent???). Your testing guy may be able to offer some simple 'advice'!.

Those numbers look to be the standard recommendations the SAP software generates and they are absolute rubbish - do you have a copy of the SAP report you could post? A good consultant should have the knowledge of construction technology, sensitivities of the SAP calculation and suitable cost effective upgrades.

PUR, PIR & polystyrene have no acoustic properties. Mineral wool should help here but if this is a beam supporting a wall above and bearing on another wall below flanking transmission may be in issue.