ADLIan

Foam (insulation) backed plasterboard must be mech fixed to wall (otherwise it’ll just fall off in a fire!)

Vents required at high and low level - normally eaves and ridge.

The Building Regs (Engalnd & Scotland), advice in Timber Frame Construction (from TRADA) plus other sources all refer to the use of a ventilated cavity behind render systems (on a carrier board) onto TF construction. Render on insulation on the structural frame is not recommended and has not been for many years.

As a general rule if OSB or ply sarking is used this is classed as having a high vapour resistance so 50mm vent air space required below the sarking/above insulation (even if breathable membrane used above sarking). See BS 5250.

Above diag only refers to masonry leaves not timber frame.

The EPC states a GSHP has been used so the COP (though we do not know if manufacturer data or default value used) has been accounted for.

Just a few comments on the IoW house EPC; I know the assessor and he is vastly experienced, an expert on SAP and very unlikely to have got it wrong The assessor does not list the recommendations in an EPC - these are automatically generated within the EPC software The SAP rating is a measure of energy cost. Electricity is a lot more expensive than say gas within SAP so will impact (negatively) on the rating The SAP rating is not used to assess Building Regulation compliance (which is based on CO2 emissions) Difficult to say why this house has such a low EPC as we do not have the detailed information but I imagine it is due to being all electric, the large glazed area, no air leakage test (default used) and a poorly specified/designed MVHR system (which can increase energy use!) A house can have a poor EPC (D or E) and still pass the Building Regs

The SAP rating is based on energy cost so choice of fuel has a big impact. Electricity is more expensive than gas in SAP (though impact is offset by efficiency of ASHP) so SAP/EPC score will drop.

Software I use gives a decrement delay of just over 12 hrs for that construction

Also remember that the energy conservation standard under Appr Doc L1A (assuming England) for new build is much onerous that Appr Doc L1B for extension/conversion works. Check carefully with BCO exactly what they require.

Lots of references to Code for Sustainable Homes and Zero Carbon Homes in the Fen Drayton doc. As these are both dead in the water I doubt these conditions are now enforceable. I believe JSH had a similar issue and had the condition removed.

@JSHarrisJeremy - I would refer you to manufacturers test data on this one. Insulation in floors under the DPM can also experience the same hydrostatic pressure as basement walls (unless very well drained)

I didn't want to scare monger just giving information that is freely available from EPS manufacturers. Your house will not fall down or be ejected into oblivion but the thermal performance of the EPS will be slightly worse. I do not have shares in any DPM or insulation companies. I am aware of Peripor this is one of the enhanced moisture resistance products. If the manufacturers are OK with a free draining sub base then fine.

The comparison of EPS floor insulation to swimming floats is irrelevant - as a floor insulation it has a critical technical function to fulfill over the lifetime of the building. In constant contact with moisture, say under a DPM, EPS can absorb water something like 3-5% by volume (there are some newer products with enhanced water resistance where this figure may be 2% or better - these are often coloured pink, green, blue etc to make them look like extruded poly). This moisture absorption can add between 2-4 mW/mK to the thermal conductivity of EPS. Other physical properties generally not affected hence their use as inert fill/void formers.

I assume the eps here is only acting as a ‘cushion’ so probably not

DPM required in ground floors (GF) with just about all insulation types. DPM not required on upper floors but polythene VCL/slip layer/separating layer needed with insulation under screed

Same applies to pur/pir. Again check MIs and BBA certs for use in GF

Yes eps does need a dpm under it. Check MIs and BBA certs

South of the border I come across similar planning conditions quite often - not many 'zero carbon' but lots of 10% (inset other values to suit!) better than TER under the Building Regs. Normally applied to developments above a certain size - 5 houses, 10 houses or total floor area on site. As ever major house builders/developers appeal this as it will make the scheme 'uneconomic' or otherwise not feasible and as if by magic the condition disappears.

I doubt the planning officers who come up with these conditions are aware of SAP, it’s outputs and SAP ratings. From past experience they only look as far as Appr Doc L1A and the CO2 emission rate (DER) - get this to zero or less and box ticked. Would be interesting to see the exact wording of the condition.

No dpm required for upper floor but you will need membrane above the pur - acts as slip layer and vcl

EPS needs DPM under it too.

PUR/PIR has no acoustic properties so do not use this. Fully fill the studs with glass wool (check with manufacturer that its the right type). To improve things further add 2 or more layers of plasterboard each side to add mass to the wall or consider use of resilient bars to decouple the plasterboard from the studs.

Don't know the exact construction of your caravan wall but the decrement delay would typically be approx 0.5 hr! Decrement factor of about 1

The BBA logo should include a number, normally in this format 'Certificate No. ??/????' at the bottom. You can check on the BBA website that the certificate is real and is valid. The packaging on the product will also include the BBA logo and number. Once outside the packaging however very difficult to prove if BBA certified or not - if the boards are printed with manufacturer details, shift codes etc this can help traceability. The BBA will take action against abuse of the logo but I imagine with the growth of Ebay (and similar) it's almost impossible for them to follow every case.