Dan F

If everything is cost+, what is your builders incentive to complete the project as quickly as is feasible? How about chasing sub-contractors; why should builder worry about managing/chasing/replacing sub-contractors (e.g. electrician) if the project taking longer doesn't impact him? Surely there is a risk that things just drag on and on?

I have 230v Loxone dimmer configured for "trailing edge" driving some bollard lights on the front drive. They dim down to 8% before they turn off or start to behave weirdly. Don't know if it's the fittings that are good though, or the Loxone dimmer. Most of the LED drivers (downlights, low-level lighting and LED strips) support 0.1% dimming, others 1% and some track lights at 5% (which is a shame). Results at such low level of dimming with LED tape and been dissapointing though in my case https://forum.buildhub.org.uk/topic/33333-led-tape-varying-brightness-from-different-modules/.

We used 200mm centres even though not strictly required given low heat-loss. 200mm is also slightly easier to install as you just follow the mesh, which is our case was also 200mm. We didn't go under any cupboards/island/stairs, can't remember why, I guess MBC advised not to, although in hindsight this is more important for UFH-in-screed than lower temperature UFH-in-slab. The main thing is to 100% avoid anywhere where they may be fixings into the slab. TBH, even if you don't you'll still be able to run at very low flow-temps, especually with 200mm centers.

This is the one I saw mentioned somewhere I think. https://www.altecnic.co.uk/drytraptundish. Was it @TerryE that had a thread on these the other week?

Gaulhofer Inline Aluclad. Greenbuildingstore did the psi calcs, assume they are accurate. 0.040 W/(m·K) is pretty standard and is used as a default by PH consultants if they don't have calculation. The cill number 0.023 W/(m·K) is very good though, not sure why this is significnanlty better.

I tried this, but with with UFH in 200mm concrete reaction time was too slow for room thermostat. Next approach I wanted to try was external control (with hysteresis) using slab temperature instead of room temperature, but Vaillant (at the time anyway) didn't support any sort of external control for cooling leaving me with no option but to control cooling via ebus using slab temperature (with target temp based on outdoor temp) The day ahead calculation was added afterwards as an optimization to ensure the slab wasn't cooled too much if the following day wasn't going to be as hot. This was really only required because of the huge mass of the slab.

If you want to do things like directly control flow temperature and/or limit compressor speed etc. programmatically then ebus integration is going to allow you to do more. Also, when it comes to cooling the standard controls (and associated API that you'd have access to via myVaillant integration) are pretty limited and don't use weather compensation making cooling control with a passive slab very hard. Over the summer I implemented my own external control (via ebus + loxone) that used slab temp and day ahead forcast to control cooling. I used on/off control with hysteris to target a caclculated target slab temperature rather than weather compensation. This yeah though, I'll have a go at implementing weather compensation for cooling.

I haven't use the myVAILLANT home assistant integration. This only works with the updated myVailant gateway and mine was only upgraded last week. If you want full geek-level access to everything though ebusd [1] is the best option given Vaillant don't offer a modbus interface. It's not vaillant supported and can be a little tricky depending to up and running, but it does have Home Assistant and Loxone integration which makes it easy to use once you have configuration sorted. [1] https://github.com/john30/ebusd

Sorry @Thorfun I didn't use any of the whitewing stuff, or any SSR's either actually. So prefer not to make assumptions, and instead leave it to others that have used these.

If you have a PHPP model, this will actually estimate interior humidty with both options. This is what ours says for 305m2 TFA house in south-east with 4 occupants and Q600. We went for ERV based on this and no complaints. ERV: HRV: (If i plug-in Scottish Highlands, these numbes don't change.)

Ensuring window are propertly installed and foam/compriband has no gaps at all and that the airtighess is all good, are all more important. If you do have void behind reveal board internally or externally then yes or course it makes sense to stuff it with insulationn or spray foam, but I wouldn't go out of your way to do much more than this.

We have a MBC twin-wall build in the process of being certified. We uses Gaulhofer windows from @craig. At one point in the process someone insisted that we should calculate psi values for windows junctions: - Window cills without any additional insulation (but with MDF cill internally) were 0.023 W/(m·K). - Window jambs without any additional insulation were 0.040 W/(m·K) Can these numbers be improved? Yes of couse they can, but these psi values are already fairly good and you're not going to improve them by a massive amount with the additional reveal insulation. Lets say you did half the jamb psi value to 0.020W/(m·K) In our model that only saves 0.25kWh/m2.yr. (about £1.50/yr given 300m2 and ASHP heating off-peak @ COP 4). So, if it's easy/cheap do it, yes. But otherwise don't worry about it. Also, why internal only, can you not add insulation externally in reveals too? I'd use whatever material you are using for rest of internal/external walls, and then add insulation behind, rather than use a different material for reveals.

I never used any ferrules on cat6, or anything solid-core for that matter.

I used them. Given space isn't quite so tight above presence sensors no real need to use the gel crimps, you can if you prefer though.

We are also using tunable white tape and DALI tunable white drivers. No noise whatsoever from ours, but we do have issues with consistent dimming https://forum.buildhub.org.uk/topic/33333-led-tape-varying-brightness-from-different-modules/. How is your dimming? Dark Light Design are just up the road from us and supplied some of the profiles we used (we used someone else for design). Have you spoken to them?