A_L

@MortarThePoint In case you don;t have it - https://www.pcmproducts.net/Encapsulated_PCMs.htm in particular look for 'BoardICE'

Windspeed reduction is affected by porosity. Different porosities have their maximum effect at different multiples of the windbreak height so google 'windbreak porosity'.

It can go under the slab. In either case there should be a DPM somewhere below it and a slip layer immediately above it. https://insulation-uk.com/floor-insulation/ground-floors/concrete-slab-floors PIR for floors has a compressive strength of 140kPa for 10% compression, 1% compression (more realistic) will be around 45kPa (or about 4-5000kg/m2) so O.K. except for load bearing walls https://insulation-uk.com/assets/5405_floors_bba-certificate_nov2018.pdf

@newbuild I would want to see the jamb/sill/lintel details to mitigate thermal bridging by the bricks

@Jilly , K5 is a phenolic insulation with slightly better insulation characteristics than PIR. With Thermalite as described the U-value is correct, even slightly conservative.

What block specifically as this is quite low. Typical lightweight aggregate block gives about 0.26 Up to 50mm of fibrous insulation would be OK. A polythene VCL or foil backed plasterboard would add reassurance. Compressing insulation destroys its properties.

Passivhaus, 3kW Willis heater and off-peak/TOU electricity tariff.

Do not think so. Some finger in the air stuff. Current building regs imply about 45kWh/m2.yr for Target Fabric Energy Efficiency (TFEE) for terraces - pages 5/6 - https://www.zerocarbonhub.org/sites/default/files/resources/reports/Fabric_Standards_for_2013-Worked_Examples_and_Fabric_Specification.pdf or about 3150kWh for 70m2 property. If 20% in January then an average of 20kWh/day and twice average on anyone day not uncommon.

Unlikely, a well sited 4kW array will generate a max of around 30kWh on a 'perfect' day. All of this would increase 750l by about 34°C

Foamglas is totally incombustible with a reasonably low conductivity, (about 0.04W/m.K). https://www.foamglas.com/en-gb/applications-and-solutions/interior/wall/tiles/b-i-wall-render-tiles A possible alternative if available is Diathonite Evolution render (0.037W/m.K) https://www.diasen.com/sp/en/p/diathonite-evolution.3sp

A house that at most only requires intermittent heating even in Dec/Jan. I am concerned that it will be subject to overheating in summer because of the low decrement delay of the structure. What is the compass bearing of the double height glass wall you mentioned?

That depends on your objective. The U will be 0.13, very good but not a 'no heat' value.

Like @andy I would go for Tescon, but this one with primerhttps://proclima.com/products/bonding-agents/edges-and-corners/tescon-profect/system-products#sub_navigation an alternative might be a non-setting (usually butyl) mastic e.g. https://www.tradebuildingproducts.co.uk/products/145-butyl-rubber-sealant?variant=39251952599193&currency=GBP&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&utm_campaign=gs-2020-04-21&utm_source=google&utm_medium=smart_campaign&gclid=EAIaIQobChMItOKwiL3H8AIVS-PmCh1wKwJgEAQYHCABEgJFNvD_BwE applied between the edge of the board and the slab

Hello, 1) Are you using default values for thermal bridges? 2) What ventilation rate have you assumed?

1) No this is where a VCL should be. 2) The hipped areas would have warm roof characteristics but since you have other areas not really I cannot see why, but it should be insulating enough to prevent interstitial condensation in the internal layer, but it should not be less vapour permeable unless very carefully designed

A metallised breather membrane above the battens could add 0.6m2K/W (about 15mm of PIR or 25mm of loft insulation) and taped will provide air tightness. A liquid applied air barrier with a vapour permeability appropriate to its position applied to continuous sheet layer could provide air tightness.

Unless the ground floor ceiling insulation is for sound insulation then I would reduce it to 25mm of insulation or perhaps an aluminised membrane with a 25mm airspace above the upward facing shiny layer as heatloss downward to a heated volume is very limited and is largely radiative loss. If the first floor ceiling really only has 75mm of insulation I would double it if PIR or make up to 250mm if fibrous insulation.

PV = Photovoltaics = Solar panels (Electricity producing) ?

Depends on your situation. Makes connecting 3.68-11.04kW of PV without complications. DNO's do not want heat pumps with an output typically more than 14kW to single phase supplies.

Yes, though their outputs are less. Relative to 70°C outputs at 30°C/13.5%, 40°C/32.1%, 50°C/53.0%, 60°C/75.8% for rooms at 20°C and 'ordinary' radiators

What shape is your house, Bungalow/1.5storey/detached villa? Even an energy efficient 'cube' will need more than 6kW for CH alone if built to given U-values and 5m3 ventilation

Yes PIR is consistent, thermal conductivity 0.022W/m.K (maybe 0.023W/m.K)

If a condensation risk analysis to BS5250 is O.K. then not required.

Decent explanations here - https://www.greenspec.co.uk/building-design/decrement-delay/ Spreadsheet decrement delay calculator - https://www.concretecentre.com/Publications-Software/Design-tools-and-software/Dynamic-Thermal-Properties-Calculator-(1).aspx I find it 'buggy' but it might just be my ancient Excel, Or lightweight rooms-in-roof in summer

A 9l/m shower is about 22kW. How about fitting waste water heat recovery (WWHR). The en-suite and upstairs bathroom could be fed into a vertical system with 60% heat recovery and the downstairs 45% heat recovery. So about 9kW each for upstairs and 12kW for downstairs. So any two should be easily within reach of a 35kW boiler. https://recoupwwhrs.co.uk/ https://showersave.com/