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I have checked BR497 (I have the latest copy). This document states "In all of the examples modelled, the inside room temperature is taken to be 20°C and the external temperature is taken to be 0°C. For simplicity, these are the usual temperatures to use when modelling, but other temperatures can of course be used. Note: the ψ-value and temperature factor, g, are not affected by a different choice for the internal and external temperatures..." I don't know why -5 is I will send a note. The I-Joist flanking elements in my drawing are compound assembly and do not show the repeating elements,. The I-Joist bay itself is also in the report at 0.0391W/(mK), so the report itself looks complete to me. With respect to repeating elements BR497 states that the approach I have taken is correct, which is why I did it that way. Indeed, BR497's own example follows this approach and it states that drawing every stud would be over modelling; "Repeating bridging perpendicular to the junction (§3.1.3.2) can be ignored entirely if either: the bridging element's thermal conductivity is ≤ 0.5 W/(m·K), or it doesn't bridge the primary insulation layer." I'm not sure if you are providing a critique of my report or the software or if you are saying when you where an assessor you would have resorted to default values if given this report. If it is the last of these I don't think there is anything technically wrong with the report but I would welcome anything that would give you real technical grounds under which you would be able to justify default values and non acceptance of the values presented. Since I have to do a SAP10.3 assessment this feedback would be very helpful. If you just don't feel comfortable because you don't know the product that's fine. New products appear all of the time and the cost of doing psi-values should not be a prohibitive, as it is now, so I personally welcome this approach.

Thank you all. Definitely going to go custom to our measures once the screed is in! For a couple hundred quid difference it seems a no brainer.

Rendered concrete block outer leaf, 50mm cavity, Rockwool insulation between 140 studs, 40mm PIR, 25mm service cavity, resilient bars, plasterboard. Inexpensive and very effective. Less than 400mm.

All build methods can achieve that. Specify exactly what wall thickness you want, because its normal for say 140mm, nothing stopping you saying I want 200mm, then do it in I beams or posi joists style. If restricted to 140mm and then apply counter battens to increase wall thick and get rid of most thermal repeat bridges. Then any high density insulation you want.

So these properties are all owned by a single person with no plan to sell separately? If you wish to preserve an easy option to sell separately it sounds a fair bit more complex than otherwise. If operating as a pooled resource there may be options to get more efficiency out of the system. (Multi-tenant inverters exist, someone posted a link here recently).

It's a slow section of un-electrified line (I believe 50mph), with no points in the proximity. I don't hear any 'clacking' and from what I can see its welded rail. So I believe the main noise will be external from freight diesel engines and squealing of freight wagons. Thanks all - sounds like best to avoid PIR then 😅 The downside is it narrows the field a lot in terms of TFs from the usual TF suppliers, which are high performing thermally (but aren't twin stud cellulose). Aiming for high airtightness, insulation levels and convenience (e.g a subcontracted package) was leading me towards a TF from one of the usual suspects. But would consider ICF if it ends up being a better compromise. For noise, where do we would think ICF ends up compared to the twin stud cellulose?

If that is the case, make no provision for them. Do not suggest to tenants that they are authorised to install batteries. A world of liability for you.

Here you go @PSC88.

If I did an AC transmission system the temptation would be to make it a non battery system and leave fitting of batteries to soak up the excess something for the tenants to do if they wish. This might be easier with plug in battery systems.

There are 4 houses in a loose crescent around a "green". A field backs on to the "green" to the north with a high hedge The panels are being fitted to comply with the EPC regulations and get each property to. "C" grade 1 house is a good candidate for normal E/W roof solar being a bungalow with a low pitched concrete roof. The other 3 have problematic roofs. Either not good aspect (shaded) or not good enough condition to allow solar to be fitted with out a new roof first or both But a ground mounted array could be fitted in the "north" field out of sight (and far enough back so it's not shaded by the hedge. I figure it's easier and cheaper to install and maintain one array in a field than 3 arrays on 3 roofs. And then for the bungalow I have to decide if it's cheaper/easier to put panels on the roof Vs chuck some more up in the field array and run a cable to it (that would be the 100m one. The others are closer to 50m) Strictly speaking the batteries are not needed as the EPC system currently only accounts for the panels and inverter - you get no points for batteries. But it gives so much extra benefit to the tenants it's hard not to justify it beyond the purely mercenary view.

There are two incompatible standards for wiring the connectors. As long as both ends match it works, but if you mismatch and there is a non-standard power setup on the cable you might be in trouble. (it's safe if there's no power feed or if its POE standard)

I guess if you wanted to try it, fit a Cat 5 / 6 plug assuming standard colours. If it doesn't work buy a new cable, deny all knowledge and report a fault (and this thread can be made to vanish)

Buying a "standard" staircase of fixed rise always struck me as odd. Unless you are VERY lucky it would never work, unless you design your floor levels around the staircase. As above stairbox etc will get what you actually want, made to fit.

You could always add a bit more screed - but that cause many other issues, now I have written it down.

Thanks everyone. Probably overkill but it's done, onto the next thing. Happy Sunday to you all.

In general ethernet is 'safe' even if miswired. I hesitate a little as in the case of Starlink they transmit power over the cable as well. If this is done in a standard way then no issue, if non-standard then potential issue. (I think Starlink is fairly standard but have not checked and wouldn't want to take the chance without being confident) So to be safe the best thing to do is to find a guide on how to terminate the cable specifically tailored to the exact model Starlink antenna you have.

You or the BCO won't need to measure anything, 25mm is a lot, the momentary heart attack stepping off the bottom step will alert them something's off!

Would agree normally, but multiple houses was mentioned, so would assume one string per house with it's own inverter. Unless @Beelbeebub is doing lots of kW per house. But not knowing the full layout logistics will decide the final cable spec

Use it up 😀

It does back onto the new bedroom (eventually). I've got plenty of acoustic wool left, so?

Yup. You’re now 18th ed lol. Go get some stickers for the van

No point in insulation unless it’s back to back with a bedroom or other habitable space. You’re inside the heated envelope so just lag the hot and cold pipes.

Just a couple of comments on the attachment after a quick look through. Standard external temp is normally 0 Deg C rather than -5 though this probably makes no difference. Also there are timber elements missing from the junction detail.

Thanks guys, doing the job now. Should I fill up behind it with rockwool while I'm here? There is nothing behind this stud bay, the pipes are further along the wall. Brick wall is internal.

Tell you what - that's a massive understatement. What I mean is I've created a custom 3d engine that would be commercial grade - yet not 1 line of code. That is the real power of AI. I see plenty of youtube/reddit "wrote this in 5 hours with Fable from 1 prompt". Some are believable some are slop. But most are relatively simple (still impressive that Ai can take "write me a really good minecraft game with dinosaurs in it" and still produce something). But use it properly from experience and build it up layer by layer rather than the final product from 1 prompt and its a phenomenal tool. The accomplishment here is WELL beyond my technical ability. But the "difficult" parts the code and horrific maths aren't my burden 99% of the time. I'm still in awe of what's possible. Must also admit it can take some effort - occasionally days on 1 feature to be correct. Or bastard bugs... we had a few mountain tops going black as you approach. No obvious reason some would and some wouldn't. Check all the render stuff/textures/lighting everything me and Claude could think of. Nothing obvious. Found it out of frustration!. The ray march on water can shoot a ray so far that it can hit a mountain top. Essentially at that point its a NaN so plots black! - what a bast!. Water affecting a mountain maybe 4km away in real space. That kind of bug finding without Claude (as I've done many a time when a software engineer) its pure torture and can literally take weeks to find...