ADLIan

PUR or PIR doesn’t really matter as both come under the above Standard and both still combustible. Difference is in the chemistry, PIR slightly better thermal and fire performance compared to PUR but still burns..

BS EN 13165 which covers the manufacture of PUR foam was introduced in early 2000s and referenced BS EN 13501 for the assessment of the fire performance. Both Kingspan and Celotex continued to use BS 476 data (which was no longer relevant) hiding behind the Class 0 surface spread of flame rating. Note Class 0 is not even a BS 476 rating! Hence the issues at Grenfell. Finding the Euroclass fire rating for these products was not made easy simply because the D or E rating would have revealed them to be combustible. From memory the other PUR foam manufacturers did use the Euroclass system as soon as it was introduced.

It’ll be fine. Crack on. £600 extra??? No wonder we’re cynical!

Don't see what the problem is - if its OK to be used vertically why not at an angle? Only has to support itself until the ceiling finish goes in as ProDave says. Perhaps they make more money on the Metac!! I also doubt lack of BBA certification will be an issue and never had a problem with this construction as the application is covered in the Appr Docs and relevant British Standards

Also add the chemicals they (may) use to deter insects and improve the fire performance

See BS 5250. If a suspended floor it requires ventilation. At a stretch a ‘suspended’ floor could be designed to have insulation pumped in afterward but it would then effectively become a ‘solid’ floor requiring a dpm (correctly joined to dpc) and positioned to protect the insulation. Probably simpler to build it correctly. I’m sure the bba certificates for these flooring systems will require ventilation without exception.

The gshp and pv will keep the co2 emissions down but there is also a fabric energy efficiency standard and if other U-values are not up to scratch you may have problems. U=0.2 in a floor is not good. Have you had a SAP assessment done as this will give insulation requirements and fabric efficiency numbers. Does your bco have the sap numbers to confirm compliance with Regs?

Mineral wool roll or batts with a conductivity o 0.035 W/mK or better are normally rigid enough to be self supporting as ProDave says (to do with density). I think we all know of the fibreglass you refer to - probably made not a millions miles from you!!

75mm PUR sounds to be the very minimum to get through Building Regs - would expect at least 100mm and as above 150mm+. I'm not aware of U=0.20 being against any flooring requirement, 0.25 is the worst acceptable. What does your SAP report say? Normally PUR in a floor requires a dpm below and another membrane above - check with manufacturer instructions and BBA certificate install instructions

The test method for thermal conductivity accounts for thermal drift and worsening of lambda over time often found with PUR, Phenolic and XPS foams. Declared values should reflect long term lambda (20-30 years)

DS(TH)4 and DS(-20,-)2 are short term (48hr) dimensional stability tests at elevated temp and RH or at low temp (-20) as spec. Has nothing to do with long term shrinkage often associated with pur products, newer chemical formulations may have cured this problem now (???)

I still cannot find any reference to differentiate single dwelling or multi storey/multi dwelling

Thanks Dave. Can you reference that statement please?

The NI Regs and technical documents are woefully out of date. Post Grenfell. England, Wales and Scotland quickly updated the guidance and I do not think Class 0 is now referenced. Class 0 is not a BS 476 classification but a ‘made up’ classification within the Approved Docs. Both Celotex and Kingspan hid behind this classification despite the manufacturing standard for PUR foam not referencing BS476 at all - should be BS EN 13501 but this would have shown their products to be combustible (Euroclass C or D?). Hence the post Grenfell sh*t storm. Note that many building products are now manufactured to harmonised European standards (BS ENs) which do not use BS 476 fire tests.

Thanks PeterW. Beat me to it with that reply. We need WWilts to confirm if we are under English Regs.

In many walls, if constructed to relevant section of Appr Doc B, the cavity closer around openings does not need to meet any particular fire rating. Hence the use of plastic, PUR, EPS and similar cavity closers. Pretty sure the Scot Regs are similar.

Its been a while since I used THERM but those GF U-values do not look correct - the U-value is more dependent upon the size, shape and edge conditions of the slab (plus any insulation). I would expect the ground floor of a 'typical' dwelling to have a U-value of approx 0.12 W/m2K with 200mm of EPS in it, adding vertical edge insulation would be of little benefit to the U-value in this instance. With no insulation the U-value would be approx 0.65 W/m2K, adding vertical edge insulation perhaps reducing this to 0.45 W/m2K. The external wing insulation would probably have little effect on the U-value - it is more for frost protection in colder climates.

I don’t think AD B references Class 0 any more, Euroclass reaction to fire should be used. If so your BCO needs bringing up to date post Grenfell.

Remember that SAP rating estimates the energy use and cost of a house under standardised conditions so that the energy efficiency of houses may be compared - in this respect it is similar to the mpg rating of a car and is very unlikely to reflect an individual's occupancy, heating pattern, temperature settings, hot water use etc, etc. The RDSAP system for existing houses is not fit for purpose simply because the fees have been forced down to such a low level. Assessor probably gets less than £50 to travel to the house, do a 'full' survey and then collect the correct evidence to get anywhere near an accurate assessment, hence corner cutting and the easy option of ticking 'default' values. @saveasteading Can you point me in the direction of ASHP assumed to be used for cooling too? I'm not aware of this one.

See this far too often with this type of product, only real solution is to rebuild. What manufacturer is it from? You could ask them for advice on install instructions along with BBA certificate - may give you leverage with contractor. Assume you currently have a U-value of 0.19/0.20 expect this to increase to 0.23/0.24 (the theoretical correction for bad install). SAP assessor will be able to run the numbers and see what insulated plasterboard would get you back to 0.20 or better.

The sound insulation to the intermediate floor looks ok, pretty much straight from AD E. Cavity wall spec will not give U=21! Perhaps nearer to 0.28?

The ACD figures for linear thermal bridges are worst case so would use dense block inner leaf at the floor/wall junction so the 'mistake' is covered in the energy assessment. The use of aircrete would improve things slightly.

It's not a U-value at that point it is a linear thermal bridge or psi-value that is calculated using 2D thermal modelling. Doubt the thickness of the perimeter upstand insulation would have any effect. That detail looks to be very similar to the Accredited Construction Details giving an 'approved' psi-value of 0.16 W/mK. You need to check what psi-value was used in the energy assessment

Moving from aircrete to dense concrete will increase U-value from approx 0.25 to 0.28 (exact wall construction not known). As an area weighted average for the whole wall area the impact is probably negligible. The effect at the floor/wall junction can only be estimated if the psi-value is known and this will depend upon the thermal properties of the materials and the exact geometry of the junction. Only if you know the psi-value that was used in the original energy assessment can you estimate the effect of the different block type.

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