Nickfromwales

If you do this as meticulously as you can, and get a score of <1.0 ACH, then that is absolutely going to be the best time and money you have spent of the job. You can have 1000mm of insulation in a draughty house, and still be sat there with the heating on full and be cold. Airtightness is where the rewards are really reaped; then you'll need MVHR and THEN the MVHR (HR) will look after you for life. Spend on 'fabric first', and enjoy the benefits long term. Quality doors and glazing next, then bags of solar PV after that. Prob after that will be a nice kitchen for the other half so you don't get murdered before the ROI is calculable, lol .

To add: 100mm, and with only 1x layer of reinforcing steel mesh too Thicker at intermediate junctions and ring beams etc, obvs.

Not IMHO, and even more so as it's the North elevation. In my opinion, you've been lucky elsewhere. Vapour is supposed to be arrested at the fabric connections, to seal the room, then the cosmetic layers get applied afterwards and decorated. You cannot compare this to a DPC as the DPC is at the foot of a wall only with the remainder of the surface left to 'breathe', so "no" . Next steps are: Go and scream loudly into a pillow so as to not frighten the kids, Take everything off and do it again properly. Drink beer when done. I genuinely think I should have worked as a therapist

@Nick Laslett HAS got this, and it's doing great, is what he's saying. Not sure if you're confused there, sorry. FYI @zzPaulzz, I have done a number of MBC PH TF M&E installations, (I got recommended directly by MBC or otherwise got awarded the project after MBC engaged), and there has been UFH in a 100mm constructional slab on EVERY SINGLE ONE . I have worked with many SE's to date, and found Hilliard Tanners to be the most approachable and pragmatic by far (including myself designing foundations for ICF builds with insulated rafts + UFH etc) and they accommodated my methodology; only once they had suitably scrutinised everything I had sent them and they were then 100% satisfied to produce a design that we could then use on site to instruct the groundworkers to build the foundation from. I've NEVER fitted expansion gaps on a 'passsive raft', NEVER cut expansion gaps in anything other than much thinner and non-constructional screeds, and most were tiled over. Zero cracks / other evidence of cracking etc whatsoever. I always leave it a full 6-9 months to allow the slab to cure before applying the tiles, other floor coverings can go down much sooner, but the builds normally progress sympathetically to that timeframe being acceptable / possible. The running temps of the UFH in the raft are just so low the damn things don't move much at all, if anything! The MBC PH TF I have just moved clients into has a flow temp into the raft of 26oC, and I'll bet that gets dropped back 1-2oC by next winter, once they've got the house bone dry and properly acclimatised. 140m2 L-shape slab.

Not in my 30+ years "on the tools" have I ever seen this done, sorry.

Guess what you're doing tomorrow then

Oh! I just re-read the OP, then it gets worse. Defo shouldn't have left the other layer of PB in there, it'll be acting like a sponge and the moisture will then trap and..... it'll only get worse.

I think this may be one contributing factor, as the VCL should really be behind the plasterboard and continuous as part of the fabric of the property. If you paint a VCL over the plasterboard, then airflow and hot / cool convection can occur in the gaps between the insulation and the PB.

Hi and welcome. If somebody on here can't think of a way to do it, it can't be done lol

I install M&E systems and "renewables" for domestic clients who are, primarily, self building, some up to, and some at Passivhaus certified standards. I do not have a home that MVHR would work in, it's a airtight as a colander. The saying "builders house gets done last" is pretty accurate lol. One day.... The 'effectiveness' is decided at the design stage, and nothing gets actually fitted which doesn't do what I promised it would. I got a nice little award to stick on the fridge from the good people at the Sussex Heritage Trust for my M&E achievements on a £~4m Passiv / NZEB project, so I guess it must have all worked . Either that or the system blew up and killed everyone lol. Part O now gets far more attention as the lid comes off the UK's dire understanding of these things (the repercussions of building a highly airtight and very well insulated home). Worst at it currently are architects and the clients themselves, some don't understand it at all, some don't want to "set fire to the money" installing equipment they think they won't / do not need.... These heat / cool units go immediately prior to the fresh supply manifold, before the air gets delivered to the room. They don't need to do much, (if there's a quality MVHR unit with a high % efficiency rating for heat recovery) so with clever design and a bit of know-how / prior experience, these can be put in to work with barely any controls etc (dumb climate control), and then they just go about their business. In a true PH or thereabouts dwelling, I will often install a 1st floor thermostat (where there was no requirement / need for 1st floor UFH etc), and then put a zone valve on the heat / cool battery that services the 1st floor; this requires a second supply manifold to segregate the upstairs rooms (again, all done / decided at the design stage). For a smaller dwelling you'd just use the 1st floor stat to kick cooling into gear, dependant on a 'cool capable' heat pump having being specified, and it being on already doing cooling via the slab; you just tee off that primary circuit and pump a supply to the heat / cool battery.

I bought all the kit from CVC Systems. I'll ask for the product details when I speak to them next, as it's quite a few invoices ago There are 2 row / column, 3 row / column versions, giving different 'power' per unit, so I size according to the M&E requirement. Random internet pic: This kind of thing. This one is a heat only, as it’s not got a condensate drain.

Yes, IF you want it to be MCS etc (as far as I know). I'm not 'in the industry' enough to know if these little blighters ever go 🔥, but I assume MCS had stipulated this for 1 or more 'good reasons'. This advice was of 2019, but it had actually changed at the time or I asked and it was found out afterwards /whatever, so worth noting at the very least I guess? My 2 cents is to fit them where they can be accessed btw, but MCS (apparently) says otherwise.

There can only be one king 🤴. 😘

He’d have to drive 10 mins to find out

The 330 is certified for use where you need to be ‘airtight’ and is closed cell, unlike cheaper open cell foams from the sheds. The open cell stuff can promote wicking of damp / moisture, which you don’t want It’s also far less friable and much more robust. Normal foams will allow you to simply scratch away at them with your fingertip, but the 330 is a much tougher product.

But, without it people would be using cheap BZP fixings to hold solar panels, badly, to roofs. Because people like cheap short cuts. If one of those broke free and hit somebody you held dearly…. What then? Then you’d be screaming “why isn’t this regulated?” 😌. If your house burned down, because an optimiser set your attic on fire…..? Regs are there to stop people doing things poorly, badly, or downright dangerously; this isn’t just to save them, but also to protect property and 3rd parties. That’s been done here numerous times Where have you been? lol Any mcs certified company would likely not appreciate you taking to meat off their bone, given their company running costs / overheads etc, and most would (should) refuse to do that. Plenty of people out there who will do as you ask, they’re running the gauntlet unless they have evidence of every single thing you did from A-Z, including proof of fixings used etc. After it’s all installed, how the feck would they know?

If you click on a comment / post, then highlight it, an option to quote selection will pop up. Click on that and you're off to the races

When I contested it on another downstream project, because I like the idea of possible points of failure going where I can get at, I got a firm FO. Apparently MCS guidelines said (then?) that they now need to be with the panel with the factory leads from the optimiser attached directly, un-bastardized, vs connected via the 'extension leads' I had the fitters make up to set these in the attic plant space. If I ask someone to MCS a solar PV install for me, I have to bow to their terms, so the next one had the optimisers under the panels. The fail sate with them is negligible anyhoo, so it's not like these things are dropping out 1 a year etc. You can 'address' the array with optimisers, so if one does snuff it you know exactly which panel its behind.

Yup. Bad ‘cracks’ go across the timber (a snap), but splits along the length that run with the grain are completely normal and are common place (naturally occurring). All good 👍

Random Internet pic. These are dotted all throughout the cavity. A ferrous metal band (tie) usually with a twist in the middle to create a drip off. These rust and then track damp across, which is why the problem from the interior is so pinpoint to specific locations. It’s like someone poking a wet finger in your internal leaf of brickwork.

You’re no longer allowed to mount the optimisers remotely, I did this on a previous project, when it was ‘permissible’, but it was frowned upon by the solar company that I was instructing. The optimisers are only needed if there’s split elevations on the same string, or shading. If you have optimisers it allows you to address each panel, so if a panel fails you can identify its location. If you got a solar PV panel such as the ones I mentioned above, then you’ll be at > 90% productivity in 30 years from now, guaranteed. Why accept diminishing returns or possible early failure from buying cheaper Chinese stuff, even more so when you’re already saving on the slates etc?? Poor place to economise imho.

Why do you say that? I’ve recently specc’d a large dwelling with GF and FF in hollow core concrete precast decks, with a service void below. If somebody wants a ‘solid’ masonry deck then let them fill their boots If posi joists aren’t the local (Bahamas) flavour then nobody will know anything about them.

Who what in the where now??!!?? @Boyblue, you pay for the hotel and beer and I’ll come out and build it lol. I worked on a cruise liner out in the Caribbean, and sailed around the islands, was amazing. Repairing the open deck cafe roof, with 2 pairs of sunglasses on to stop from going blind with the sunlight 🌞. Was sad to come home….. 🥥 🏝️ 🍻

Ok, so a bit over 400mm. Appears to be a cavity wall, so I now would put money that your damp is from ancient rotting metal cavity wall ties, which are tracking moisture / damp.

When you factor in cost / cement products being imported and carted around, and the time and effort etc, then chasing services into the blockwork for 1st fix, they’re not actually low cost (stud work is cheaper, better, faster, and promotes installation of 1st fix services with ease. 🤷‍♂️😜.