ADLIan

IIRC phenolic foam should not be used under timber (ply/chipboard) flooring. Floor would need battening throughout to take it out of load bearing path.

Latest Approved Doc L has U=0.18W/m2K in extension wall. Looking at approx 150mm of mineral wool or 100mm PUR

Might be better spending your money on lower conductivity insulation, 0.032 W/mK. Look for ‘32’ in the product name/reference. Also check that your wall tie with its small cross-section is suitable for 250mm cavity, you may have to look at a heavy duty tie with larger area. Teplo tie may offer little benefit bearing in mind the cost.

Adding insulation under a beam & block floor changes it from a suspended floor to a ‘solid’ floor. This is OK provided there is a correctly detailed DPM under the insulation - possible in a new build but impossible in a refurb or upgrade. The Energystore system is approved for new build only, not upgrade work. As above, an expensive solution looking for a problem.

Why not 175mm mineral wool batt at 0.032 W/mK? Will give U=0.15 W/m2K with aircrete block inner.

Appr Doc L limits the glazed area of an extension, go slightly over and you will have to use high performance glazing/improved fabric insulation and use the area weighted average u-value method to show compliance. Go a lot over and you’ll be using full SAP calculations to show compliance. This may give an idea of overheating but SAP is not a very sophisticated tool in this respect

Full SAP output is used to show Building Reg compliance and create the EPC for new build dwellings. Full SAP calc is also needed for new dwellings created by conversion but normally only to issue the EPC (sometimes needed for Building Reg compliance too). EPC is needed as part of BC sign-off.

Under the 2021 version of Approved Doc L intermediate floors with heated floor systems require thermal insulation (as well as acoustic requirement).

May be yellow glass wool. Waste product was ground to make fibres that were injected into cavity walls and blown into lofts. Can you see individual fibres?

Don’t do it!! Frowned upon by BS6229 & BS5250 and doubt insulation manufacturer would support it without lots of caveats. On your head be it.

I greatly doubt that you would get a UK based insulation manufacturer or waterproofing system manufacturer to promote a hybrid flat roof, not without many caveats! They are specifically warned against in BS 5250 and BS 6229. The Scot Regs push true warm roof detail (and avoid cold deck).

Window supplier need to provide test data to confirm window performance. Calculated U-values can be used but these must be done by a BFRC certified window thermal modeller.

Because it’s an input into the SAP assessment.

Sorry no - been a few years since I worked in that sector. From memory BS EN 13165 on PUR manufacture gives info on gas tight and non-gas tight facings and their effect on thermal performance. Gas transfer into/out of the foam matrix at the edges has little impact on aged lambda.

Most of the blowing agent loss, hence loss in thermal performance, is through the top and bottom faces and is accounted for in the declared lambda value. The foil facings slow this process hence foil faced PUR has a lower lambda than product with glass tissue or bituminous facings. Edge losses are minimal. The foil-facing is a complex laminate of al foil, kraft paper and polyethylene and is adhered to the uncured, liquid foam in the manufacturing process. Adding a self adhesive foil tape to the edges would not be gas tight and would make no difference.

No. Waste of time and tape

50mm mineral wool slab in brick/brick cavity wall is woefully inadequate. Would expect at least 100mm, probably 150mm under 2021 version of Appr Doc L. As above, timber frame can be insulated in cavity but 50mm clear cavity must be left assuming masonry outer.

0.16 W/m2K is the worst acceptable for roofs under the 2021 Appr Doc L1 so 0.16/0.15 are both 'OK'. Probably will not help get compliance though if they are that high as the 'notional' house uses 0.11 W/m2K. Would need offsetting by more insulation in other elements.

Lower thermal conductivity = better thermal performance. Thermal conductivity of PUR is lower, better, than that of EPS. To get the same overall thermal performance 300mm of EPS would equate to about 175mm (not 100mm) of PUR.

Problem is that magply is not a ‘cement’ board it is based on magnesium oxide. Problems were identified with these ‘MgO’ boards several years ago including not being compatible with some render systems. Several warranty providers, including LABC and NHBC, banned their use.

+1 to that. It is now down to the SAP assessor to police this, not something they signed up for as this is a Building Control function. In the absence of this photographic evidence assessors must revert to default SAP numbers at which point the house will probably fail under Appr Doc L and the assessor is the messenger (who probably will be shot!). Because of this, and a whole raft of other admin procedures, I will let my SAP assessor status lapse in the next few months.

Photographic evidence of build quality (insulation levels, dealing at junctions, preventing thermal bridging etc) is now part of the Building Regs. Requirement of the 'new' 2021 Approved Doc L, effective mid 2022, for all new dwellings.

Only for new build. Not sure how you’d retrofit a dpm under an existing b&b floor?? Under existing Appr Docs and British Standards adding the insulation layer under b&b floor makes it a ‘solid’ floor which requires a dpm.

'SFUF' has a core thermal resistance of 0.8 m2K/W. This is equivalent to approx 18mm of polyurethane foam board - I'm sure we'll all agree totally inadequate for a heated floor.

No real rocket science there! Report needs a different title too - sends the totally wrong message.