Mike

My guess is that it would flex too much on a ceiling as you tried to apply the plaster, but maybe not. On a wall it's possible, but there you have a rigid support behind it. BTW, not mentioned above is the need for a airtightness membrane; I'd choose Intello or similar. There are other threads on the topic if you need more info.

It's defined on page 5, table 0.1 (my bold text): 1(c)(2)(4) Dwellinghouse that does not contain a habitable storey with a floor level a minimum of 4.5m above ground level.

I'd guess that the weak point is likely to be the junction of the insulation and the wall, not the plasterboard to the insulation; the wall is unlikely to be perfectly flat (so the bonding patchy) and the surface might be friable. So, if I was concerned, I'd add some mechanical fixings before fixing the plasterboard.

For me 4000K is the ideal temperature, everywhere. But above all, be consistent - that is, all lights in a room that will be turned on at the same time should be the same temperature, otherwise they just look odd. So if you like 3000K, stick to it.

I've not used them myself, but AFAIK they have good vapour permeability; I'm not sure about moisture buffering. However, for a standard ceiling you normally wouldn't worry much about moisture so, if I had spare cash I'd choose to upgrade the insulation instead, by using either flexible wood fibre (e.g. Steico Flex) or hemp (e.g. IndiBreathe Flex). Both of these handle moisture better than synthetic insulation and also provide a much improved decrement delay (non-technically = resistance against summer heat). Hemp edges ahead of wood fibre for moisture handling, while wood fibre edges ahead for decrement delay, but not a big difference. Don't hang the light fitting from the plasterboard; you need to fix it through the plasterboard / wood wool board into a joist, or into a nogging fixed between two joists. 9.5mm is OK if your joists are no more than 450mm apart, but it will be a little less robust & have a little less fire and sound resistance. I'd choose 12.5mm unless cost is a factor.

Clay plaster does have better moisture buffering qualities and can moderate daily variations but, if you have adequate heating and ventilation, that won't make a big difference. If you don't have adequate heating and ventilation, consider those first. Unpainted clay plaster can look good though! For more, see my comment in this thread. ^ This.

No space in a 1,750 square foot house? I'm not the only one that's fitted one in an apartment a fraction of that size; they really aren't that big. Could go on the wall or ceiling of the laundry room, or study next the hot water tank, or the kitchen, or the largish entrance hall, or the WC...

If that's a pair of steels over that window (difficult to tell from the resolution of the pic), then I'd remove the outer one and span over the window with the timber frame instead, to cut the thermal bridge. At least it doesn't look like a single steel across both leaves. BTW, make sure that the rafters over that ridge beam are adequately secured; I hope that the SE has specified something for that.

In that kind of build the air sealing won't end up being external; external insulation goes over the top of what you see there. Or at least the majority would go on the outside. You could put some between the studs but, following the UK rule-of-thumb, it would be no more than 1/3 of it avoid the risk of condensation within it and hence the need for a separate internal VCL.

Time to radically reform the system. As reported in https://www.parliament.uk/globalassets/documents/commons-committees/public-accounts/2018-07-09 - MHCLG Report to the PAThe Role of International Evidenc.pdf

You're right; it is standard practice to use a non-return or waterless trap for the reason you mention, but Zehnder's instructions sometimes suggest otherwise. For example they require only a U-bend with water seal in the CA 200 manual, but a non-return trap on my more recent CA 225 model. Avoid a dedicated water trap as it's likely to dry out. A good illustration of the principle, although my CA 225 has a 20mm drain so requires an alternative pipe adapter. A hole drilled through a rubber bung is doing fine so far.

I guess it's a different model number? That one seems to be single channel 25A? Indeed, sticking it over a bedroom wouldn't be a good idea with regular contactors.

I was going to follow Terry's lead before I found that silent domestic contactors are readily available in France, for a premium. I've got Legrand 412501 (way below the list price) & presume they're solid state. My understanding is those in the Shelly are. Though if these are destined for a loft then clunking may not be an issue and would save a few £s.

I've did similar. Bbattery powered camping shower + shower tent + paddling pool + drill pump. It gave a pretty good shower.

Hmm. The Pro 4PM is rated for a maximum switching load of 16A per channel, subject to (1) a maximum of 40A across all channels at once; (2) leaving 10mm cooling space around it for currents over 10A and (3) using solid core heat-resistant wire (4) adding a snubber across inductive loads. However the Live input has a 2.5mm² connector which would normally be fused at 16A or 20A, limiting the total continuous load. IMHO it would seem wise to use the Shelly for control and contactors to handle any serious loads.

Correct, the Shelly only switches the contactors. You need an RCBO & contactor for each immersion, plus another RCBO to protect the Shelly itself.

As an alternative, consider the Shelly Pro 4PM for the remote control functions, used to switch 3 x 25A contactors (1 for each immersion). If they won't fit in your main consumer unit, fit an auxiliary one in the loft.

If you have the cash and have already done / plan to do other obvious thermal improvements, then it's worth considering - unless you can apply external wall insulation, which would be preferable. If you're able to withstand the disruption of IWI then presumably it would be part of a larger improvement scheme? With an insulated cavity wall the risk of condensation is greatly reduced / eliminated (depending on insulation thickness and provided rooms are adequately heated and ventilated). If it turns out that there is a significant risk then any gypsum plaster needs removing. Ensuring the airtightness of the existing wall (and all the junctions between the wall and other materials) is more important than a vapour control layer, as airflow through the structure is likely to cause much more condensation than the absence of / gaps in a VCL (as well as causing heat loss). If you add a VCL too, then only choose an 'intelligent' one such as Intello. There's a long meandering thread here that's worth reading. It relates to solid walls, but still useful: Plasterboard & regular plaster are vapour-permiable but, as mentioned above by @Redbeard, regular vinyl paints aren't - you'd need clay-based / lime-based paint to maintain permeability. With an insulated cavity wall permeability is normally less of a concern.

One of the first attempts to do that in the UK was the Beddington Zero Energy Development, better known as BedZED, completed in 2002. I must have visited it in 2003. It used passive stack ventilation, aided by wind-driven roof fans, with plate heat exchangers for passive heat recovery - nothing electro-mechanical. Airtightness 2.5 ACH at 50 Pa. 300mm wall floor & roof insulation. 133 kWh/m² to 331 kWh/m². As this was a very high-profile pioneering development follow-up surveys were carried out. There's probably a better source but I've tracked down a thesis that includes some of the results here: Lessons Learned from the BedZed Development, J Young. TLDR: Almost half of the survey respondents did not think the ventilation system at BedZED was effective at removing moisture and smells. Condensation or mould was reported by 6 out of 18 residents surveyed (though 1 had bunged up their air intake to stop cigarette smoke entering).

Yes, the white is efflorescence caused by the deposit of salts from the brickwork onto its surface as the moisture evaporates. Efflorescence is harmless but can take a very long time to disappear. It may also appear damp as the salts themselves can absorb moisture from the atmosphere. Bush it off every few months or, if you prefer, buy an efflorescence remover (a mild acid) from your local builder's merchant; it may require more than one application.

We once had something similar, requiring the contractor (us) to provide bacon sandwiches for all site meetings, though I don't recall any mention of the china...

Maybe that's the time to turn it on then - keep the vents in the areas you're not living in well bunged up and go for an initial approximate balancing to suit the areas you are living in.

it's realistic enough to have spent several hours successfully doing it myself. Even a tiny hole in a high wind feels like someone's blowing cold are down a straw at your hand - no candle required :)

It can identify where the main air leaks are so that you can fix them. I'd rather do that than rely on Aerobarrier at that stage. High winds make for a good pre-pre-test (or post-test) too; go around all the junctions slowly & feel for air leaks & mark them or fix them on the spot.

Yes, I've seen that happen and adding insulation will resolve it. Be very cautious about running the MVHR - as @JohnMo says, you don't want to be drawing dust into the system. However it is possible to have it running when there's no work going on if you take some precautions & accept the risk, as I have. While work is in progress and until dust settles, keep it switched off; during work put plastic shower caps over the terminals; add sock filters to the extracts (a good idea anyway). Also consider upgrading the MVHR return air filter to better protect the heat exchanger - from (normally) ISO 16890 Course (old G4) - to ISO 16890 ePM1 (old F7 & as normally used on the air intake), which filters out at least 50% of very fine dust and 85% of medium-sized dust (up to 55% of sawdust, for example, is too fine to be trapped by a course filter). I've not done this myself as I suspect that these smaller sizes (<10 microns) would be fine enough pass through the heat exchanger without building up significantly, but I've not looked for any research on the topic.