MikeSharp01

Other than thinking that a properly constructed Larsen truss is practical and therefore structurally OK I cannot comment further on them. On construction - our I-Joists are glued, so the flanges are grooved and the web (9mm OSB) is glued into the groove under pressure (in the factory) so no nails. Where we do have nails (and a lot of them into the flanges) is on the sheathing on the cross walls. 3.1mm dia nails at 50mm centers everywhere for racking strength. So I guess our SE must have thought that that racking issue was the biggie.

So is your building 532m3 ? Not sure how the shape of the building make any difference to the maths but I can see why it makes a big difference to the build challenges. Our build is 465m3 so next stop is to work out what our holes can add up to

I guess the 0.31 is the passive house methodology eg air change rate h-1 @ 50 Pascals.

That's interesting, what I was wondering then is how big a hole is .31ACH?

Unless it's for sharing against solar gain. The new building regs seem to have a bit to say on this in the overheating portion.

So where were the leaks that were still left?

Says the man with water that is softer than a babies bum to start with. So really it's move to the Scottish highlands, build a house, install some PV, design and build a diverter - then fluff any amount of towels for a short time - but only when the sun shines... Sorry I guess you already did😁.

Filling in with solid insulation between Larsen Truss or I-Beams is a pain, Where we are not having blown in cellulose I made EPS 100 infills which effectively made our I-Beams flush than I could push in the 0.032 insulation batts without the folds around the step and any gaps.

Yes we brought ours as self building is unpredictable. In the past the scaffolders quote for the number of lifts and the estimated time with a weekly / monthly overrun price. Never had one with an under run discount though😁. The thing to avoid is piecemeal call backs - IE small unplanned mods to the scaffold. A late scafolder of my acquaintance said that the most piecemeal changes came at window fitting because people were not clear about where / How high & big they were at the outset and then it was when the groundworkers wanted to dig a new trench because some customer wanted the loo pipe moved.

That is a start but maybe, like weather compensation, you need to get ahead of the activity and the people. So predicting who will be home and what sorts of things they will be upto so you can prepare the best case for the combination. Although that also implies that none of them will be happy if they all prefer it slightly different.

This is another cruncher because the strategy is just one strategy when actually you probably need more than one - I guess that weather compensation was put in to allow a more flexible strategy but it seems a very crude scheme from those that I have looked at and the push up / down idea is something that needs also to be dynamic but relies on humans to adjust it. Its feels like we need some sort of heuristic system (not human) that learns from the responses to the various stimuli and so tunes the scheme to the users and the building.

man after my own heart Recently the more I fiddle with numbers around ASHPs (Despite an innovator / early adopter mindset) the closer I come to just following in the footsteps of @TerryE and using a Willis heater - the only thing it cannot do is cool on the few days a year our PHPP outcome says we might find cooling useful!

If you have a double socket on a ring then a competent electrician can add a switch fused spur to that and you could have that fitted inside the cupboard close to the device with appropriate cable run and protection for the cable, if needed, back to the double socket.

I was trying to pre-placate the Units police! Yes I did I assumed 6months of heating @ 8 hours a day H+DHW and 6 months of just 4 hours a day DHW. Low figures but was for the place we are building IE Passive standard)

Just did a back of fag packet thought experiment calculation on the real COP on a 5Kw (COP 3) unit (worst case) with 300W vampire load load and assuming 6 months of heat and DHW and 6 months just DHW comes out at 2.02!

Also interestingly I was looking at the parasitic loads that we may have in our build and was wondering just how much energy the home automation system was going to burn.

Interesting read...

The LG units recently highlighted here have scroll compressors by the looks of it.

NO - "The moral of that story is when viewing as house, get the current owner to go to the the middle of each room and jump up and down......"

How does this situation work with full filled rafter builds - like ours which are 300mm deep and will very shortly be filled with warmcell then battened over and plaster boarded to create the vaulted ceilings, so none of our rafters will be inspectable either?

You could run your ASHP in reverse and feed the cold water around the UFH to cool things down and perhaps add an online cooling battery to the MVHR but you cannot get much cooling at 'MVHR flow rates. JS Harris showed the the UFH cooling was effective in his build.

But there is heat loss so ensure you get a very well insulated one.

?????

There is free software to help with this - https://www.dialux.com/en-GB/download

its got a 35% movement factor hence the jelly feel.