MJNewton

Great, thanks everyone!

Ah, yes, okay - will take a look. Found this stuff which might work too described as a cut-to-size washable mesh filter (for extractor hoods):

Would that be good for grease? I was under the impression carbon has really small pathways hence why it's good for trapping smells?

Does anyone know of grease filter that I could put inside my kitchen MVHR extract vent? Ideally one that would sit inside the 125mm duct so I can keep the current terminal. Rather than bespoke item I wondered if I could just use some generic filter media of some sort, cut to a round shape and shoved up inside?

Slight correction: it was actually a ply deck (the OSB was used below the insulation).

There was an 18mm OSB deck and he put matting just over the joints.

Good question; it doesn't seem to be all that widely available when I looked around for where I might get it from in future. I know my roofer got his from Raven Roofing Supplies although there's no mention of it on their website (which is odd as they do training courses for it too). I'd get it from there as they's local but I'd suggest others contact Eagle Insulations as they are the UK distributor I think.

Yes, all fine thanks. It's only been 18 months though so maybe a bit early to comment on longevity which is probably what really matters. It's been really tested though over the past year with the rain, and the fall isn't the best (builder made an error with the firrings.... grrr - still winds me up) so if there was an issue I'm sure I'd have seen it now. I'd definitely use it again - easy to apply (a roofer did mine but next time I'd DIY) regardless of complexity if surface/upstands/etc, no seams, tough yet elastic etc. The only things that do bother me about it is 1) hardly anyone else seems to use it (the manufacturer told me they sell very little to the UK compared to other countries and, for what it's worth, stating that the UK market does tend to hold on to its traditional building methods so it's been a tough market to break in to), and 2) I do wonder if Desmopol is all that different from those 'quick fix in a can' paint-on roof repairs that even the manufacturers state are for temporary use only. That said, Desmopol does have a BBE certificate and comes with a 15yr (or is it 25?) guarantee that can be extended 5yrs at a time by an additional coat over the old one every 10(?) years so I'm as confident as I would be for any flat roof covering I think. Here's a pic (of the roof lantern really but's got most of the roof in) after around a year:

I was going to ask if that was a euphemism but as I read on then wondered if it was true so decided it was insensitive to joke about. Got to the end and realised it was a wind up but I'd be lying if I said you didn't have me for a minute!

Is there a BR requirement for maximum ventilation? If not then just whack the system up to full and measure the flow rates to ensure the minimums are met and done with it. I doubt there's a need for a balancing for BR compliance too.

I think you might be expecting too much from MVHR - particularly a single room one - in terms of their ability to cool (or heat) a room. With the limited heat capacity of air coupled with the relatively slow flow rates that's not their raison d'être. View them more for their cost-effective air freshening and dehumidifying qualities and you can't go far wrong. Don't get me wrong; MVHR can really help keep a closed-up room/house fresh and in some circumstances they can have a slight active cooling effect (ironically when the summer bypass isn't active and the outside air is warmer than inside) and we do feel what could well be a psychological cooling effect from ours with that constant flow of 'fresh' air, particularly on warm still summer evenings/nights. To summarise: MVHR isn't the same as air conditioning, if that's more what you're after?

Ah okay. The ones I've been looking at (Integral Evofire) are sealed by the bezel on the ceiling side and have a piece of glass over the bulb. I guess they use different methods by the sounds of it.

If the fittings are fire rated aren't they already airtight (sufficiently so for what's required here at least)?

I've used both the red Airflow Airflex Pro and green Blauberg semi-rigid ducting and whilst they were nominally the same in terms of size and interchangeability the former was more flexible and felt like a better quality product.

Thanks everyone. One less job on my list... ?

I could just do that. I always like to get things ready for tradesmen so they can just jump straight in to what I'm employing them to do. It's a big room though and not too many holes so he'd probably have done them before I'd even got the kettle boiled.

Interesting about spray foam. I did consider that but wondered if it might be considered a bodge? It's a 'done thing' then? Would it still resist knocks without cracking?

I shall be getting a plasterer in to skim some previously dot-and-dabbed walls and as I've made quite a few holes where sockets have been removed, new cables routed etc, was wondering what plaster I could use to fill these prior to him doing hia bit? Maximum depth is around 40mm. Noting the difficulty getting plaster at the moment are there any viable alternatives? Or does anyone have any idea how long it'll take for supply to recover?

As Jeremy says it sounds like there might be a design/installation here. We live in a semi-rural location - silent at night - and our system is completely inaudible in normal background mode. Even on boost you can only really the airflow which I would regard as fairly inoffensive, regardless of what dB value it might actually have. I actually find the noise to be psychologically beneficial on a hot stuffy night as it makes me feel like the house is being freshened/cooled probably more than it actually is! Incidentally, ours was a retrofit and so we had to make some compromised in terms of installation (positioning, routing etc) and so I would expect a new build to be even better.

Welcome! Do ask away - you won't be the only one to benefit from the discussion and answers, and we all like to read about what others are up to! ?

Hmm.. That was my original plan to be honest but to be honest I got a bit nervous about a method I'd not used before. You think it'd be better then? And by 'regular' boards do you mean 12.5mm? There will be five downlights; fireproof fittings though so not completely open like some. Appreciate they will still compromise the acoustic barrier though.

Thanks everyone - maybe it's not so strange a route to take afterall. I do actually have a few joists on 600mm centres (not sure why - I guess it saves on a joist or two in an area that doesn't otherwise need them) and so the 15mm should be better suited (notwithstanding the point about noggins likely sufficing). On the supply front I must admit to bit having asked the local builder's merchant (they're all closed, I think) and so was only searching online which might not be representative. I think I'll continue with the plan.

I am putting a new ceiling into our extended 'family room' and was planning on using 15mm plasterboard rather than 12.5mm. The reason being was that I figured it might provides benefits in terms of improved acoustic attenuation for the bedroom above and slightly better fire rating. Perhaps even some benefit regarding stiffness and strength? I've got a plasterboard lifter so the extra weight when installing isn't of concern and I probably only need around a dozen 2.4m x 1.2m sheets so the extra cost should be minimal. However, I didn't realise that 15mm PB doesn't seem to be widely available, even aside from the current supply issues for all gypsum products at the moment, and so I am beginning to have second thoughts if it's not the 'done thing'. Also, where it is sold, it is generally tapered edge and yet I was going to get the whole thing skimmed and so would be wanting square edge. Am I do something odd here? Just wondered if anyone has any thoughts on whether 15mm would provide the assumed benefits, or should I just stick to 12.5mm?

You had me 'til that point! Whilst price and value and two separate things that need weighing up against each other, for me that sort of money is too much to justify given it doesn't give a perfect solution in terms of avoidance of vendor lock-in, bespoke knowledge etc. Everyone is different but I would prefer to go down the open software route even if it means a steeper/longer curve. £2.5-3k would go a *long* way in terms of buying a variety of open products and open source software to drive them, and leave a fair bit for a holiday to recover from it all!

Note that if it is warmer outside than in then keeping the heat exchanger 'in loop' will cool the incoming air as heat will transfer to that being extracted/exhausted. Your bypass should therefore not be activating in such a scenario.