A_L

@willbish, about 18.3kWh/°C

@newhome try here https://thinkrenewables.co.uk/sofar-ac-battery-storage

Hybrid heat pumps have/require heat meter(s) as payment is made only on the renewable output https://www.ofgem.gov.uk/system/files/docs/2018/05/essentialguidetometering_may_2018.pdf

@Russdl , a couple of comments about your spreadsheet. First 38mm studs at 600mm centres are 6.3% timber by themselves, you have to allow for noggins (if present), wall plate, sole plate, top and bottom of frame, cripple studs at windows etc if these are within the heatloss areas of the walls. BRE recommend a 15% timber fraction for conventional timber frame walls, reducing to perhaps 12.5% if many of these are not present/moved outwith the wall area, into the floor/wall, wall/ceiling etc thermal bridges. See page 8 attached pdf. In balance I believe you have a 'twin wall' timber frame construction, with little/no timber in the 'Cellulose insulation 2' layer. BR_443_(2006_Edition).pdf

Roof mounted wind turbines are colloquially referred to as 'chocolate teapots' for good reason, they simply do not work. Wind turbines require non-turbulent air which they don't get on a roof and if located in an urban/suburban location the wind speed is to low to be effective. The vibrations are also likely to keep you awake at night!

Polystyrene is an insulator for two reasons. First it has a reasonably low thermal conductivity on its own. Second most of the insulating effect comes from reducing air movement, i.e. the small cells enclosed by the polystyrene do the work, this in fact is how most of our insulations work. This is enhanced by the fact that we use it in thicknesses up to several hundred millimetres. Polystyrene can be produced like polythene as a clear plastic film, no air cells. It works in a heat exchanger because it may only be a few hundredths of a millimetre thick. It also obviously has a large surface area. Thus it has an adequate heat exchange. In reality a mvhr heat exchanger is many heat exchangers thermally in series, each with about a 50% efficiency, the low thermal conductivity along the length of the heat exchange surface actually helps to isolate each series heat exchanger from the next/previous one, this is in fact an advantage over a metal heat exchanger.

The absolute minimum is a 25mm cavity, with battens to carry insulation and 75mm of PIR (to achieve U=0.3). Mineral wool will be 50% thicker to have the same effect. I would not use 2L2 on the cold side of the insulation as it is a plastic sheet and when taped at the edges a vapour barrier and in the wrong position. I think 100mm PIR would be reasonable but it may depend on how much floor area you are willing to lose.

The cavity will be so that water vapour passing through the insulation can be carried away by air movement before/after condensing on the cold granite You need to be confident that warm room air cannot bypass the insulation and get to the cavity, this can be difficult with intermediate floor/celings The idea that granite is breathable is well ............................ Internal insulation in this situation requires an effective vapour control layer (VCL) on the warm side of the insulation and/or an insulation with a significant vapour resistance itself To achieve e.g. current building regulations you would require at least 300mm of Bauwer light! If I had to I would use PIR/PUR insulation hard onto the granite with a VCL External Wall Insulation is much simpler although I can understand if you want to/have to keep the external appearance in the 'granite city'

Assuming from this a 450m2 house to current building regs with mvhr levels of air tightness then 15kW would be plenty at -3°C

Slopes 1,3&4, as far as possible evenly split between (1+4) and 3, probably microinverters

Forget about minor efficiency differences between mono and poly crystalline panels. The output per kWp of panels installed will be similar and other factors much more important in annual output. Amorphous panels will output about 5% (or 50kWh) more per year per kWp but their lower efficiency will mean 30-100% more physical area required. Exact value will vary depending on which amorphous panels and with the efficiency of the silicon panels you are making the comparison. So 8kWp could easily occupy 60-80m2

I am assuming 220m2 floor area, 0.11-0.15 fabric U-values, T shaped bungalow with cathedral ceilings (from blog), 5kW (maybe even 4kW) for instantaneous heatloss plus perhaps 2kW for DHW (worst case). So as suggested by quote for 8.5kW Ecodan 12kW NIBE oversized.

@Russell griffiths , have you looked at this? https://www.greenbuildingstore.co.uk/products/compacfoam-200/

Depending on loading and situation here are a number of possibilities. https://forum.buildhub.org.uk/topic/4302-improvement-on-block-and-beam-foundation-insulation/?tab=comments#comment-68339

@Dreadnaught & @HerbJ Yes it should also prevent loss of heat exchange efficiency when temperature falls below zero in winter, down to -6°C according to Paul. I am sure at one point Paul claimed down to -20°C. Repeating the links I gave in an earlier post on this thread. Theory here:- https://www.paulheatrecovery.co.uk/components/moisture-heat-exchanger/ Edit: no longer seems to work http://waermetauscher.paul-lueftung.de/en/product-information/enthalpy-exchangers-erv.html 2nd Edit: @Dreadnaught managed to get a copy and saved as PDF PaulenthalpypageasPDF.pdf

Would sealing the top and bottom of the cavity not be sufficient? Assumes sides are already sealed by CWI?

Which MVHR do you have? At least some can be optionally fitted with an enthalpy (or latent heat) heat exchanger. This allows water vapour in the exiting air to transfer to the incoming air, humidifying it. Particularly useful in cold conditions where the incoming air has little water vapour but should also help in summer. Theory here:- https://www.paulheatrecovery.co.uk/components/moisture-heat-exchanger/ http://waermetauscher.paul-lueftung.de/en/product-information/enthalpy-exchangers-erv.html It should also prevent loss of heat exchange efficiency when temperature falls below zero in winter, down to -6°C according to Paul.

Is it to naive to ask........... - Consider two means of transport of water molecules, 1) Bulk air movement 2)Vapour diffusion. These have to be handled differently. Bulk air movement caused by say a convection current from a radiator or by an air pressure differential, carries water molecules along. Vapour diffusion occurs when there is a concentration gradient of water molecules, in this case the molecules in the more concentrated areas move to the less concentrated areas in an effort to maximise their path lengths before another collision with another water molecule. An air tightness layer therefore may or may not control both mechanisms. If it does not provide resistance to water vapour diffusion and it is inappropriately sited then interstitial condensation may occur in appropriate circumstances. Vapour Control ..... So you need roofing felt (vapour control) allowing the vapour to exit, but not return. - Not quite, you need to allow water vapour to exit but prevent the return of liquid water needs BOTH a VCL and an air-tightness layer prevent vapour leaving the house by using the air-tightness layer as a VCL?.............potentially, but this will towards the inside of the structure and you will probably need something, i.e. more membrane, to protect the external sheathing for example. prevent ingress of vapour in the same way?........vapour ingress in our climate is not normally a problem as it is usually warmer inside than out and the incoming water molecules will not condense as the Rh falls as they move inwards. And put the air-tightness layer where there are least penetrations? ..... preferable but case dependent, on the outside it must not be water vapour resistant or interstitial condensation may occur unless another VCL present on the warm side or preferably use a breathing construction which is not subject to interstitial condensation

All your windows "pass" on U-values. IIRC WER band "C" or Uw<=1.6W/m2.°C to pass. Windows are the very last place to look for "easy" SAP points, the difference between your worst and best will be marginal.

I think males of all bees are stingless, certainly hive and bumblebees are. No room for stings and reproductive organs in the abdomen. You are unlikely to encounter many though, mating requires fatal disruption of abdomen. They lay a few eggs in tube like structures and seal them over and then start on a new tube, usually immediately close by. Yes they do like hot dry conditions.

TER is 'Target Emmission Rate', the amount of carbon produced in heating a house with the same footprint as yours and with levels of insulation, infiltration and heating system as specified in the building regs. Your house DER, 'Dwelling emission rate' must be less than the TER. You specify an air change per hour rate (ACH). For passivhous it is 0.6ACH@50Pa. I suggest you aim at 1-3ACH@50Pa to make effective use of an MVHR. This is a leakage rate at an elevated pressure, the actual unpressurised uncontrolled (infiltration) rate will be considerably lower, about 1/20th if IIRC. If designed in from the start Passivhous need only be 0% to 20% more expensive.

The floor perimeter must also be measured on the inner face of the external walls (heat loss walls only).

The correct area is 12m x 4m = 48m2.

One way to look at is to say 38mm of EPS has the same insulating effect as 23mm of PIR, so not quite twice as good. The proportions hold for other thicknesses

The link does appear to make an allowance for the efficiency of converting input fuel to output heat but I am sure that the RHI payment is only based on the energy provided by e.g. the ASHP to heat the house i.e. the previous system is disregarded. It may be that a coal house, with a chimney, is draughtier and thus is assessed as taking more to energy to heat. Because you have a cavity wall the EPC will not have a EWI recommendation. Even if you had a solid wall and it recommended EWI this recommendation is disregarded for RHI purposes