ADLIan

Photo evidence of insulation, detailing, junctions etc has been part of latest Regs, in force for last 3 years. One of the reasons I got out of energy assessments - SAP assessor is now seen as the bad guy when it is really a BCO issue. You need to take it up with your BCO to see if he’ll offer some form of waiver/relaxation of the Regs

if the house is too exposed, which sounds as though may be the case, any form of retrofit cavity wall insulation is probably not suitable and would not follow the design & installation guidance for these system. The problem is filling the cavity with any form of insulation increases the risk of wind riven rain penetration in very exposed areas. Find a reputable CWI company nearby and check with them - they should offer a full survey & design package and if too exposed advise you against CWI. External insulation may be your only option but probably needs the cavity insulating to avoid thermal bypass - Catch 22 situation!!

Binder is added just after glass fiberisation (web search will show process in detail). Binder is heat cured to bond fibres in a ‘loose’ matrix hence air can be trapped. Any irritation is primarily from the fibres though newer technology produces ‘nicer’ fibres. URSA and Knauf probably take the lead here.

The 2 products are the effectively the same, glass mineral wool. The difference being the processing additives, binder & colour (which only accounts for something like 5% of the product). @SteamyTea The thermal conductivity of basalt, as a rock, is 2 W/mK (ish). Basalt is also much denser then glass which is part of the reason that stone wool is approx twice as dense as glass wool for the same thermal and acoustic performance. The mantra of 'denser = better' from one of the stone wool manufacturers is bullsh*t. They're just different mineral wool products with similar applications.

If the cavity insulation is doing its job any space behind the cabinets should be relatively warm. Don't see any real risk there.

But a multifoil will be compressed to next to nothing (a few mm?) over the stud giving little, if any, thermal resistance.

Perhaps a bit controversial but multifoils do work. The problem goes back 15-20 years when Actis was the main manufacturer and using their own spurious test method were claiming an exaggerated thermal performance. They were taken to task by the ASA and mainstream insulation manufacturers - I believe individuals may even have started court action. Multifoil manufacturers now have proper test methods (BS EN 16012?) in place and some products are 3rd party certified. The actual thermal performance is less than half of what Actis (and others) claimed in the past. This performance is based on reflective foil faces so need an unventilated airspace each side for optimum performannce, plus the core (wadding and other foils?) has a thermal resistance, though relatively low as only perhaps 20-40mm thick. With taped joints some products can create a good AVCL.

Check with your BCO - may need to be one hour from both sides. If so I greatly doubt you will find a wood fibre manufacturer with the correct test data. Remember any test will be very specific and only applicable to the actual materials/products tested.

SAP assessor and BCO will want documentary evidence of window performance including Uw value & G value (and, as above, safety glass where needed for BCO)

I assume you mean Ug value for glass only U-val. G value of the glazing is very different.

If the roof space is not being used and there is a horizontal ceiling use mineral wool at horizontal ceiling level. Will save you £1000s!!!

Also is there an option to use SI units? Written around ASTM Standards rather than British Standards so not applicable to UK Building Regs.

The section on cavities and cavity barriers in dwellings in Approved Doc B is relatively short and straightforward. Follow this and if BCO raises an objection ask exactly what their issue. Rockwool will insist that you use their insulation with their cavity barriers - if so try another manufacturer such as Promat FSI or Siderise. The type of 'cavity' insulation is not relevant.

The cavity barrier would normally be from the main stud (structural) wall through the 'external' woodfibre insulation to the back of the cladding - in this respect I would imagine there are quite a few manufacturers. There are some cavity barriers that can sit external to a non-combustible 'cavity' insulation but in this instance the cavity barrier must be tested in conjunction with the cavity insulation. I note the ply/OSB sheathing is internal in this instance, perhaps this is where some of the problem lies. In dwellings the cavity barriers are normally around openings and at each storey height and at the top of the cavity. I doubt the company linked to above will have the technical resource to comment and advise on something as specific as the English Regs & Approved Docs. NHBC and/or LABC technical manuals may help. Perhaps ask your BCO for guidance, citing specific requirement and sections in Appr Doc B.

Hi Nick - I doubt this will happen. Again post Grenfell manufacturers are very careful on what they claims. There is a big difference between reaction to fire (above discussion) and resistance to fire.