ADLIan

Nice gappy insulation - plenty of thermal bypass possible. Also cavity slabs look to have a lap joint edge profile, if this is the case they have been installed incorrectly as the lap joint should ensure water is shed outwards.

I’m not sure the additional cost of 32 grade is justified in a better u-value when installed between rafters or studs. The thermal bridging in this layer means only a very small decrease in u-value (0.01 better?). 35 grade probably at the sweet spot unless you’re really desperate for that very last bit of improvement.

Low density loft insulation is compressed more than cavity/rafter/timber frame insulation. All should expand to stated thickness once unwrapped but over or under expansion should not be tolerated. Complain to manufacturer if this happens.

Earth wool is a trade name. Google ‘timber frame roll’ for alternative manufacturers

Beware of extended lead times and price rises. Knauf I believe are on 6 week or more lead time with 14% price rise due soon.

Part E applies to intermediate floors and certain partition walls within a dwelling. More onerous standards apply to party walls and separating floors between dwellings

External gable wall becomes internal wall in extension. Was a cavity tray installed above the flashing?

PUR for different applications can have different formulations for the core and different foil faces. Check with manufacturer for suitability and if interchangeable. As regards use under screed the MIs and BBA certs will normally require a light gauge polythene sheet.

Would normally expect dpm below insulation /slab with vcl/slip layer between insulation and screed. Check MIs and BBA cert

Decent window manufacturers will give the Uwindow value (for the whole unit). See also BFRC website for energy rating of windows.

SE can’t certify product if no BS for teplo type tie. Even if there is a BS manufacturer normally has to certify as part of CE marking. Note both teplo and neutras have BBA certS I so assume normal wall tie BS does not cover these. No BBA or compliance with BS means fitness for use under Building Regs can be questioned.

That would be classed as unvent surely. Even if slightly vent, 500-1500mm2/m, the software I use still gives resistance of 0.18 m2K/W for the cavity. Suppose it depends how you define this airspace in TF - weep holes are left but any ventilation from these is fortuitous and probably can be ignored.

I've not checked through any of the above U-values but remember the calculation will be different between England & Scotland. Timber frame in Scotland requires a ventilated cavity behind the brick/block cladding which means anything external to the breather membrane is ignored in the U-value calculation (but external resistance is altered). In England this airspace is vented so the cavity and external masonry can be included - particularly important when using reflective breather membranes.

Follow the kingspan installation instructions on their website.

+1

Denser mineral wool rolls and slabs normally have a well defined thickness (not like the fluffy loft insulation). Try manufacturers websites for best products and best install method.

Ridiculous situation of local authority introducing these conditions and not having a clue what they are doing. Sometimes there is a get out clause stating if the planning condition makes the scheme not economically viable the condition can be dropped. A scheme of 17 houses near me had a similar condition dropped when the developer made a simple statement to this effect but no figures or costings to back up this statement! Has the local authority a 'sustainability officer' or similar you could ask.

I come across these types of planning conditions on a regular basis and it is obvious that they are written by people who don't know what they are talking about. You actually have 2 slightly different conditions here, I normally deal with these as follows; The 19% reduction in DER over the TER is simple and will probably mean using renewables/low energy (need to check with the planners what is included or allowable here!) The 28% reduction is arrived at by removing all of the above renewables and comparing the DER/TER (this dwelling may fail the Regs but this is not an issue for the planning condition). Ask the question of the planners - doubt you'll get a sensible reply! As above get an OCDEA on board asap to advise.

In the calculation above layer 4, TF200, needs setting to zero. The 0.77 value for this is only valid when against an unventilated airspace. This increases U-value to 0.26.

As mentioned above most BCOs probably wouldn't recognize a thermal bridge if it fell on them. Advise you to get a SAP assessor involved asap. Part of the assessment is to look at all of the linear thermal bridges (around windows, junctions of elements etc). Do not let the assessor use the overall default y-value for the effect of thermal bridges! You cannot estimate the effect by calculating the U-value at this point - 2 dimensional thermal modelling is used to assess the junction.

XPS will cause plasticiser migration in cables same as EPS - keep them apart!

An ASHP may not help - may actually make the SAP score worse!! It means your space/water heating are all electric which is about the most costly fuel (though offset to a degree by the efficiency of the ASHP).

The SAP score is based on fuel cost, as such elemental U-values do not have a great impact. The choice of space/water heating system and fuel will have a much bigger impact. Solar PV can help too. Get the SAP assessment done and see how the numbers stack up - a good assessor will advise on cost effective solutions.

Insulation manufacturers are normally exact with their U-values. Looking at the above calcs; the service void airspace is unlikely to be low emissivity (only if AVCL is reflective/foil) anything external to a vent airspace is ignored and external surface resistance set to same as internal See BR443 on U-value conventions and BS EN ISO 6946

The BBA certificate referenced above is no longer valid. Looks to have been withdrawn in Feb 2016.