ADLIan

Doesn't look to be in accordance with manufacturers instructions or BBA Certificate especially the use DPC at corners. Take it down and rebuild.

Basement U-values are very complicated calculations. The basement floor U-value is based on the P/A ratio (as normal ground floors), the depth below GL and the type/thickness of insulation. The basement wall U-value is based on the depth below GL and the type/thickness of insulation in both the floor and the wall. Perhaps contact one of the XPS manufactures (Polyfoam?)

Not in masonry cavity walls I hope!

You may have to build a twin stud wall - basically 2 stud walls back to back. Fully fill all cavities with mineral wool (at least 18kg/m3) to give zero U-value and required acoustic performance. See Appr Doc E of the Building Reg which gives typical details for new build separating walls. The acoustic standard for conversions is slightly relaxed compared to new build but Appr Doc E will give you a starting point. I believe these types of wall need acoustic testing on completion but check with our BCO.

Test sample is horizontal so heat flow is vertical. You’re really overthinking this, the insulation will perform the same irrespective of orientation. There are many other things, workmanship included, that have a bigger impact.

Conductivity of insulation materials are measured in horizontal plane, it’s how the test kit works. In the overall u-value the orientation and direction of heat flow is accounted for in the surface and airspace resistance.

All of the standard mineral wool products, density range of say 10-50 kg/m3 will give the same acoustic performance once installed in a timber stud partition wall or intermediate floor. Performance is better with thicker insulation but tails of once above 75-100mm thickness. To improve the partition further it is down to adding mass with denser and/or multiple layers of plasterboard (or the use of resilient bars to decouple the plasterboard).

There is no need to use SAP to show compliance if converting a barn or other building. The standards outlined In Appr Doc L1 for U-values, heating system efficiencies etc should be followed. A 'new build' SAP assessment is needed on completion but only to generate the EPC, there is no pass or fail associated with this step. This SAP assessment will account for heat gains and losses from the glazing but overheating is not assessed (see other thread).

I was a SAP assessor, now retired. Yes you do have to input project specific data - the defaults will really screw you over!

SAP 10, it's inputs and their relationships are very complex. You need to read and understand the SAP 10 guidance document (nearly 200 pages of fun) and the relevant SAP Conventions document - available from the BRE.

Do not use a cold roof design here. The 5m max span is mentioned in BS 6229 on flat roofing. The BS 5250 calculation method does not accurately reflect the effect of the ventilated cavity that should be present. It’s possible to get the condensation calculation to show a safe construction quite easily. From past experience condensation will be predicted on the underside of the lower osb deck. Redesign as a true warm roof.

Not really the architect’s fault. Fault lies more with the insulation manufacturer for developing a system that needs this level of dimensional tolerance.

That’s the very reason the building regs and successive Govts (and funding schemes) have not promoted AC - it increases energy use!!

The old Rockwool trope of denser=better!! Lower density glass wool or stone wool would do the same job, fraction of the cost and easier to install. MF system, resilient bars and double layer plasterboard have bigger impact on acoustics.

One of the insulation manufacturers (can’t remember which one) introduced a similar system, just with xps strips, quite few years ago. Was not a success and soon dropped!