bluebirdnick

Apologies for dragging up an old thread but I agree with this completely and indeed it is what I did above the old ceilings I was working with. But I've just seen a product call Ring Leader which looks like a neat and easy way to deal with this problem too (hence me dragging this up again). I still have one or two plenums to fit, and I'll be using these for it. On the subject of BCO: they send a different person along each time. The last guy didn't even comment on the MVHR; the one before that said he wanted to see the unit running but didn't have any concerns beyond that.

Thanks all. I have the Domus plenums too: I bought both types to see what the difference was, and in some cases I need the duct part to be over 300mm. I'd like one of those cowls - the mess these holes make is phenominal, in particular as I've boarded over old lath and plaster ceilings. But now I have a 133mm hole saw I'm not sure how I'd use the two together. I'll have a play.

Thanks Jenni. I'm beginning to think I'd not looked hard enough for a hole cutter between 127mm and 152mm! I've got a 133mm starrett cutter arriving today and I think I'd still be happier with allowing the plastic plenum to poke through the ceiling and be cut so I suspect I'll use that and see how I go. It will take me weeks to get it done from here, I had a week at home last month to get things finished but for various reasons I was unable to do much. So now I'm left trying to fit it in on weekends and with a toddler and a newborn it is going to be a challenge!

Airflow grey plastic ones, which have about 300mm of plastic duct as part of the unit. The video shows that the plastic duct sticking through the ceiling and then being cut so that the bottom of the plastic part of the duct is flush with the room side of the ceiling. So the hole needs to accommodate the outer diameter of the plastic part of the duct. However it does make me wonder if I'm doing this right. The room valves have a metal base plate that is inserted into the plastic duct and secured to the ceiling. It is quite large, but its outside diameter is clearly 125mm as it sits tightly inside the 125mm duct. Like this: So I wonder if actually I cut the plenum so that the 125mm plastic duct sits on top of teh ceilign rather than coming through it, and then poke the metal base plate up through the ceiling and into the grey duct that sits above it. I've got quite thick ceilings - probably about 40-50mm now - but the base plate is quite large and could span that gap.

Thanks. For £8 it's worth a go. I've found a 133mm one for £18 too so will get them both and see. I need to drill two holes in brick too. I was expecting that a 127mm diamond core bit would do it (and my builder has a 127mm bit), but clearly it won't. So I'll need to find one that does, and a drill large enough to do the job.

I'm curious as to how everyone else has cut holes in ceilings for their plenums. 125mm seems to be the standard internal diameter for these things, but the external diameter is wider than a 127mm hole saw. The next standard size up is 152mm which would be far too big. I've only installed one, using an adjustable hole cutter but it is fair to say that this is less than ideal as it leaves a pretty rough finish and isn't particularly accurate - fitting the metal collar became an issue as I had no ceiling to take a screw. So what has everyone else been doing? Is there some standard hole saw out there that I've simply not found? Starrett make one at 133mm which might be about the right size - has anyone used and can confirm? It's £50+ so not a cheap bit of kit. Or are people cutting them freehand with a plasterboard saw? The adjustable hole cutter just about did the job but I want to avoid using it if possible.

My choice was budget driven. I live in what is now quite a large 1930s house which we will likely extend again at which point we are going to be 220 sq m at least, so need a unit that can ultimately handle that. On the other hand - it is still a 1930s house, so I don't kid myself that I'm going to get brilliant heat recovery performance. So I need a big unit, but not a brilliant one. I like a bit of science and I am big into energy efficiency, so I am openly doing this in part to satisfy my own curiosity. I'll be the first to admit that I am doing this in part as a hobby, just to prove to myself that I can. If we can get stale air out of the house and make it a more pleasant place to be, I will be happy. If the energy bill is materially the same before and after, I won't be disappointed. BPC pushed the one you are looking at and I am sure it is superior, but they couldn't explain how or why, other than it being newer. So with all that in mind, a unit for under £800 that can cater for the house we are (slowly) renovating/extending was the obvious choice. I've not got it running yet so I cannot comment on its pros and cons, but I will say this: it is absolutely massive. Smaller than a washing machine, but not much. Fortunately it is very easy to strip down into its components, which is vital: it was too big to get into the loft in one piece but took 20-30 mins to dismantle and move. As regards installing the plenums: this is a first fix job, it would have been infinitely easier to do it when we were renovating the house (remember - mine is a renovation not a new build). We over-boarded the old lath and plaster ceilings throughout, because I like the sound insulation properties of the old ceilings and frankly it is cleaner to over-board them than tear them down. Also they had wallpaper or lining paper on them- in the last house we stripped it off so they could skim the original ceilings, but it is a truly miserable job and we vowed never to do that again. And we did the renovation 2 years before I'd even heard of domestic air ventilation systems. However if I'd always have intended to install the MVHR at the point we reovated, I'd still have cut the holes and installed plenums after having the ceilings skimmed because my plasterer doesnt like plastering ceilings with cut outs. But if I would certainly do it long before you have any finishing work done. If your ceilings are coming down then I don't imagine the mess created by cutting a hole with a 130mm diameter in new plasterboard is going to cause you much of a concern to be honest though. btw, the plenum itself can easily be cut to length with a hand saw or a mitre saw: just mark it; remove it and cut it. I'd find that cleaner and easier than using a multi-tool, but each installation will differ I am sure and there will be good reasons for using a multi-tool in other cases. A hand saw is also better at cutting the semi-rigid ducting than using a stanley knife, in my opinion. On loft height: your unit may be smaller than mine and the ability to duct out of the side may well mean that 0.8m is enough - but it does sound very tight, especially as you are actually going to need some space to work in. Just ask BPC- they should be able to tell you if it is practically possible.

Hello! Sorry for the delay in replying. It is going very very slowly. I installed the semi rigid radial ducts some time ago, in May I think. And I got the unit into the loft about 2 months ago (unconnected). But I've made precious little progress since for a variety of reasons. But this week I finally went back up into the loft. I installed my first plenum today, and as with all things relating to this project it turned out to be far harder than anticipated. The plenum is a 125mm internal diameter and 127mm is a standard size for a hole saw so I got one assuming it was designed for 125mm pipes... but it's not big enough. The next size up which is generally available is 150mm+ which would be far too big. So in the end I bought a cheap adjustable hole cutter which did cut a hole, but it is far from perfect and is perhaps 5mm wider in diameter than it needed to be. But then fixing the plenum itself; and the collar that sits between the valve and the plenum, have proven to be real challenges. I am actually quite enjoying these challenges now that I've missed my deadline wildly, and am taking my own sweet time over things. (by way of example - I need to move the unit about 5m across the loft, but there is no boarding between where the unit sat, and where I needed it to be. Rather than stripping it down and carrying it carefully over the joists which would have taken 30 mins, I instead bought 10 sheets of OSB; a pile of 100x47 timbers; and a few rolls of top-up insulation and cross-battened the loft space, topped up the insulation and boarded it over to give me a platform across which I could safely and easily move the unit. But this fix took an entire day). In answer to your questions: Paired runs: yes, to most of them. All of the wet rooms; the downstairs living room; and three of the bedrooms. My unit is in the loft, but I have the advantage of more than 3m of headroom and a cavernous loft to work in. Obviously it will depend on the size of your unit etc, but there is no way I could get mine in something under 0,8m. It needs some space underneath for condensate to drain away, and the 160mm ducting that my unit takes is bulky stuff which as you say increases the headroom needed. I'll try to share some photos soon to show you it part-installed so you can see what sort of headroom I eneded up with. My guess is that my unit would need about double the headroom you are working with. Above a bedroom: I'll give you my thoughts when I finally turn it on! The general wisdom is to avoid having them above bedrooms but if you don't have any viable alternatives then I'm not sure I'd fret about it for too long. I will be putting mine over the bathroom. I intended to house it in an insulated box, suspended from the rafters with steel wire. I am sure that this is total overkill and I've decided to see how it sounds just sat on a vibration matt on the loft floor first before doing the suspended insulated box thing.... although I do still want to do that just because it is cool. Split my order: yes and I am pleased I did. Nothing against BPC, but ordering did turn into an ordeal with them and they inexplicably dropped items off the order at random points, and didn't seem to have answers for many of my questions. The ducting place I used for part of the order has been really good -they manufactured some bespoke parts for me at a decent enough price and they seem really knowledgable which was a big help. Although BPC do sell anti bacterial anti static ducting , and I am not sure you would get it materially cheaper elsewhere, so not sure that is a good reason to split it. I wanted to split it primarily because BPC don't stock 160mm rigid ducting and my unit takes that - I didnt want to compromise and step down to 150mm.

Thanks all. The former. But the downlights are already installed. I am personally not a fan of them because as you suggest, they are a bit rubbish at providing even lighting in a room, but my wife likes them and it wasn't something I felt so strongly about. Thanks - I assume you mean for sealing up the hole in the pots? I actually have a can or two of this left over from a previous sound insulation project. I do actually have that above the new en suite, but not in all rooms. I've not got two layers of plasterboard though, and it would be near-impossible to fit it from above now. So it seems that flower pots (or plasterboard cubes) would do the trick. For those that fitted them - what size did you use? thanks

As I said in my other thread, I am retrofitting MVHR in my 1930s house. We have done quite a bit to improve the airtightness, mostly as a happy side-effect of the other work we have done, but I am now looking at what I can do specifically to improve airtightness. I know this is possibly a futile project given the age of the house and the construction methods used, but I still want to do as best I can with it. One of the big issues is that we currently have a cold loft. This will change next year when we extend into it, but for now it is a cold loft. All ceilings beneath have been boarded over and re-skimmed, and a vapour barrier installed on the cold side. Which is all very good, but then we go punching holes in it to fit downlights - about 25 in total. What can I do to mitigate the impact that these have on airtightness? The electrician has used fire rated units that take LEDs so tells me I need no "caps" above them in the loft space to shield them from the thermal insulation above, but presumably I can/should do so? You can buy plastic loft caps that look like they would be airtight, but they are very expensive for what looks like a very basic product. Would a basic upturned terracotta flower pot do the trick? And if so, presumably I would have to cover the hole in the bottom? I'd probably seal around the bottom of it too, just to make sure. I can't see why this shouldn't work, but have a nagging concern about moisture in the wet rooms getting trapped in the flower pot and condensing on the light. And what to I put above the smaller holes made by ceiling roses and other light fittings? And cables from switches etc where they come up from below? I'll be changing the loft hatch too (We need a new one anyway). Any thoughts welcome! Thanks.

As with all things, it depends! But if you are having radial ducting, then yes most people seem to go for 75mm semi rigid ducting, which runs from the distribution boxes to the rooms. The 75mm is the external measurement i.e. yes you need at least an opening with a diameter of at least 75mm. You can also get semi rigid ducting in 90mm; and there are a range of rigid ducting options with all sorts of sizes too. Airflow also make oval ducting that is shallower and meant to fit more easily between joists (I think). You can switch between oval and round too - they make connectors for that. That might save you a tiny bit of ceiling space. As regards other sizes: yes, you have a different size duct that runs between the MVHR unit and the distribution boxes; and the MVHR unit and the fresh air outside. In my case, the MVHR unit takes 160mm ducting so I'll have 160mm rigid metal ducting running from the outside to the unit; and the unit to the distribution box. You are not obliged to stick to the spigot size on your unit as you can get reducers - e.g. I could have reduced down to 150mm. For the avoidance of doubt, when I say "plenum" in my posts, I mean the bit of kit that sits beween the 75mm radial duct, and the valve in each room. Generally the plenums are set up for 125mm valves, but again - that is not a necessity and you can get room valves in other sizes too. As regards soffits: I would ask the builder where he thinks is best, as well as whomever is designing your system. It's not just the ducting itself you need to fit in, but the insulation around it too. Soffits are the only acceptable choice for me, but your roof design may make it easier/harder/impossible for you. You might want to consider maintenance from the outside too. Our house has two walls that are basically inaccessible without a scaffold so I wanted to avoid putting vents etc on those. Good luck with it!

active cooling: I'm going to see how we go, and possibly add it next year (assuming you mean the extra bit of kit that cools the supply ducts). But as I am not sure that my house is made for MVHR, I will take a look at other systems for cooling if I think we need it

In short: no. We were (still are!) doing a 2 storey side extension and the joists in that are 200mm, but I didn't touch any of the joists in the existing building. We have a dropped celing in the new en suite - dropped about 250mm; and a false wall hiding a service void of about 300mm in the en suite. I use this to get most of the ducting to the downstairs. There is then another dropped ceiling in the side extension which makes getting ducting to most of the rooms simple enough. On the other side of the house, I am going to run a duct down through a built-in wardrobe in one of the bedrooms to feed the living room beneath. The decision to drop ceilings and make service voids was unconnected to the MVHR, but it did make it much easier. The existing house was extensively renovated about 2 years ago so I want to minimise tearing it apart. Even with the luxury of extensive service voids, it is still a tricky retrofit project and I am beginning to think that the loft was the wrong location for the unit. My new issue is intake/exuaust to the outside. I have a hipped roof and I really don't want ugly metal chimneys poking through the roof (which we replaced in 2016). So that leaves the soffits, and mine are really shallow, at about 120mm. I have asked a local company to fabricate a round-to-square connector and radius bend that I can fit between the rafters - they will come back to me next week to tell me if it is possible.

Here is the link. I could only find this by using the search tool - I couldn't find it from their menu system. Same goes for the small plastic clips that hold semi-rigid ducting - once you know they sell them you can search for them but they don't seem to include them in the spec, and its not obvious where they sit in the menu system. https://www.bpcventilation.com/foam-flow-control-damper Plenty of advice on on how to install them too. Someone above has suggested (I think!) that these create noise if installed at the valve end, but not at the manifold end. Presumably you use a 125mm insert at the plenum end and shove it in the plastic pipe that pokes through the ceiling; and a 125/150/160/200 one and shove it in the metal/plastic rigid ducting that feeds the distribution box if you are doing it at the manifold end. I've decided not to order them and see how I get on for now - after all, I've got semi-rigid attenuation; drum silencers; an insulated distribution box and valves with dampers included! If that lot doesn't do the trick I'm not sure how much of an impact the foam insert will have, so I am leaving it for now and will use as a last resort if neccessary.

Thanks. They don't sell MVHR units, plenums, distribution boxes etc. They specialise in metal ductwork. I've also found another supplier that can supply insulated distribution boxes with a 160mm spigot, so between the two of them I've got everything I need for a 160mm setup.

Thanks to everyone who has commented so far- it is really helpful. On the subject of noise: my unit has 160mm connectors. Because BPC don't stock 160mm ducting and therefore don't have many items that would fit 160mm, I have been assuming that I would have to step down to 150mm at the unit. But I've had a look, and I can get 160mm ducting, attenuators, distribution boxes and wall vents from other suppliers. My thinking is that the wider pipe would carry 14% more air than the smaller pipe at the same fan speed, thus reducing fan speed and so hopefully reducing noise. But even if this logic holds up, is the difference just too trivial to matter, and am I obsessing over something that in reality will make no difference to performance or sound? On the one hand I am really reluctant to split the order and just get everything from BPC And stick with 150mm and reducers. But on the other hand, in addition to my thoughts on fan speeds above, I am drawn to the neatness of everything being the same diameter! (plus the other supplier's gear has rubber seals which I think would de-skill installation; they can cut the duct to length for me... and it is £100 cheaper).

I had assumed that I would have to adjust the flow at the room valve, or use one of those foam inserts, which I thought was designed to reduce noise, not create it!? How do I throttle it at the distribution box? My head hurts! This is a problem for me - the main bedroom is the closest bedroom to the unit, by a good distance. And it is the one room where I want absolutely no noise! My wife is already doubtful as to the merits of this system and has threatened to turn it off if she can hear it at night. Hmm!

Interesting. Is the theory that the shorter the pipe run, the greater the noise in the room? I'd be interested in the experience of others in attempts to minimise noise. As far as I can tell there are a number of components that are designed in part to reduce noise: 1) the unit itself which presumably is the origin of any noise 2) the rubber connectors for connecting the unit to the ducting to the outside, presumbly to minimise the transfer of unit noise to the ducts and therefore the area above the living space below? 3) rigid drum sound attenuators, whose only purpose seems to be to reduce noise 4) semi-rigid attenuators, which seem to have a dual purpose of reducing noise and simplifying installation of the distribution boxes 5) the distribution boxes themselves - some of them come fitted with 20mm insulation. Clearly sound attenuation is a secondary purpose. 6) the foam dampers/silencers which you can insert into the plenum and even stack in series. These seem to have a dual role of reducing noise and controlling airflow 7) the valve - some have sound dampening built-in, presumably similar to the foam damper How many of these do people actually install on each leg? Most (all?) of the insallations I have seen have the semi-rigid flexible attenuator to connect to the distribution box and many have the druma attenuators. But how many use the foam dampers, or sound attenuating room valves? And has anyone retro-fitted any of these items so have a feel for how effective any one component is? My proposed system has an old, cheap unit and they don't make rubber connectors to fit it, so that is item 1 and 2 I've failed on. I do intend to fit items 3 and 4 on both supply and extract sides, and an insulated distribution box on the supply side. I have no idea whether I need the foam dampers or how many it takes to make any difference (they can be installed in series), but I do intend to fit dampened valves in all bedrooms and living rooms. But this is all guesswork really on my part, and I wonder if this is all overkill or whether the law of diminishing returns kicks in at some point and that I will simply have to make do with a certain level of noise.

Thanks. Yes that is what they have told me, but the ducting in the loft runs across rather than along my joists and to be honest I'd rather have them tied up to the rafters anyway. I've upped the spec to include 18m of the foil-backed duct insulation.

Thank you - that looks brilliant!

Good spot. Yes we have trickle vents in 3 places. The one you can see here (the WC downstairs); the back bedroom; and the kitchen bifolds. The WC window you can see here will be removed and blocked up shortly anyway (we have extended on that side of the house so it opens up into the side extension. And I will seal up the bedroom and kitchen ones when I am fitting the unit. However the general point you make is one I have been grappling with. A 1930s house is far from airtight. We have done a lot to improve things since we bought it, not really with airtightness in mind but nevertheless helpful. For example, I ply-lined the suspended timber floor downstairs, taping joints and refitting skirting boards; replaced all doors and windows; wet plastered every wall, and overboarded and skimmed every ceiling; blocked up chimneys and replaced the roof. We have also extended on two sides (wet plastered walls with the exception of one); and rendered most of the outside walls. But there will still be loads of places for air to move around - I have done nothing about sockets, light fittings, letterboxes etc. So yeah - I accept that to make the HR part work I have quite a bit to do and even then it may be futile, but I still want a system that takes stale, moist air out of wet rooms and puts fresh air back into bedrooms and living rooms. The MV part is more important to me, any HR I get from it is a bonus!

Thank you! I love the idea on fixing the plenum to the valve first - that may well work! As regards calling - I've spoken to them at least half a dozen times, but they don't seem to address my questions on the items on the parts list, they simply remove the ones that I question the need for. But the current parts list has 6 reducers and no bends or joins for the rigid ducting runs, which makes no sense. And they don't seem to acknowledge my requests for dampened valves, drum attenuators etc and I am not getting responses to questions like whether I can put valves in wardrobes. This isn't a criticism - I get the feeling they are working with skeleton staff because they did say that some of their design capability was reduced during lockdown. But lockdown is also something of a golden opportunity to get all of this installed so I do want the kit delivered asap! They really have been good otherwise and I would actually recommend them (as long as we agree on a complete parts list that will work). The lagging is another thing that had been missed - they were specifying 4m of the stuff, and I have four ducts that run at least 10m through the loft space. I did send them my building control drawings and they did draw up something of a plan for me, but it didn't really work. They had ducts running through RSJs, and were assuming that solid walls were cavity walls capable of carrying ducting from loft to ground floor. I have sent them more detail and photos to show where it is much easier to run ducts but had no revised drawings. I assume they will materialise when I order. The other thing I have asked for but had no detail on, is how on earth I am supposed to measure airflow for the purposes of balancing the system. The calculations taht I assume they are doing are all well and good, but let's face it they will bear no relation to the actual flows!

Hello all. I am in the process of extending our 1930s house* and I am struggling a bit with ordering it from BPC. THey have had a few goes at the parts list and they keep making changes, and when I question the changes they keep changing things back without explanation, which makes me worry that they are not going to send me a complete system. I could do with some advice on how these systems actually get installed as it will go a long way to helping me understand what they are proposing. This is not a criticism of BPC who have been super-helpful, but I do want to make sure we get it right first time around! Apologies for the length of this post. I set out first some basic details of the system I need; and then the questions I have which will help me finalise my order. To be clear - these are all questions I have already put to BPC over the last few weeks, but the chap I am speaking to (who is super-helpful generally) has not been able to get me answers to some of these. Any advice or comment would be very much appreciated! Thanks. Nick --------------------- Basic facts: - 4-bed, 2 bathroom detached house approx 200m2 - Semi-rigid 75mm radial ducting is now installed. No other kit has been bought yet - Unit to be installed in the cold loft space above en suite or bathroom. Roof is hipped, so I will stand the unit on the loft floor as wall -mounting is problematic. - Unit is an airflow BV400, for reasons of cost. - We dropped the ceiling in the en suite by a good 200mmm. All of the ducting for the ground floor rooms, with the exception of the living room, runs from ground floor to loft via a stud wall in the en suite. - I therefore intend to fit a distribution box for the "extract" ducting in the space created by the dropped ceiling in the en suite i.e. beneath the main joist and the loft insulation. I think this will make things a lot tidier in the loft space and mean that more of the ducting stays on the warm side of the insulation, and can be sited very close to the MVHR unit. - The ducting for the "supply" rooms runs through the cold loft space. Seems easiest to attach the distribution box for the supply side to the underside of the roof rafters somewhere above the MVHR unit itself. - External supply/intake will be in the side wall of the house, with the galvanised metal ducting run through the space created by the dropped ceiling in the en suite - again on the warm side (although not sure this really matters) - I know my house is not exactly a prime candidate for MVHR, so I am looking to minimise noise in the bedrooms and living rooms ie on the "supply" side. I want the "extract" side rooms to be quiet but I am less bothered about a small amount of noise in those. -------------------------------------------------- Here are my questions - any guidance would be much appreciated! 1) The specification initially included rubber connectors, which have not been included on later versions of the parts list. I have asked for rigid drum sound attenuators but they keep specifiying semi-rigid ones instead. As far as I can tell, the semi-rigid attenuators are used to connect from the MVHR unit to the distribution boxes, and are seemingly preferred because it makes installation easier. I cannot work out what the rubber connectors were doing on the parts list but it seems fine to exclude them. I have however asked why there are no 90 degree bends for the rigid ducting on the parts list but have had no explanation - that is surely an error? Surely I need to at least make one turn as the external vents are on a side wall, and more likely 3 turns? There are also no connectors for the rigid ducting. Again - surely an error? The longest run is about 4m to the external vents. I've questioned it but the parts list still excludes connectors. 2. And how does all of this actually fit together?! This is what I have in mind - corrections of confirmations would be much appreciated, as well as comments on the best option: Connection from MVHR unit to external vents: Option a: MVHR unit 160mm terminals --> 160-150mm reducer --> 150mm rigid ducting, including 3x 90 degree bends --> 150mm external vent Option b: MVHR unit 160mm terminals --> 160mm rigid ducting, including 3x 90 degree bends --> 160-150mm reducer --> 150mm external vent Connection from MVHR to distribution box: Option a - (simplest): MVHR unit 160mm terminals --> 160-150mm reducer --> 150mm semi-rigid attenuator -- > distribution box 150mm spigot Option b - (simple too): MVHR unit 160mm terminals --> 160mm semi-rigid attenuator -- > 160-150mm reducer --> distribution box 150mm spigot Option c - (quietest?): MVHR unit 160mm terminals --> 160-150mm reducer --> 150mm semi-rigid attenuator -- > 150mm drum attenuator --> distribution box 150mm spigot Option d - (quietest?): MVHR unit 160mm terminals --> 160mm semi-rigid attenuator -- > 160mm drum attenuator --> 160-150mm reducer --> distribution box 150mm spigot 3. Is the drum attenuator overkill? On the supply side I have an insulated distribution box, and BPC seem insistent on the semi-rigid attenuator. On the extract side I have a standard distribution box and the semi-rigid attenuator. 4. I keep asking for the dampened room supply valves to minimise noise in bedrooms, but they keep specifying standard PVC. Is there any reason why dampened valves shouldn't be used? 5. I have floor to ceiling built-in wardrobes with sliding doors in some bedrooms. Can I install the room valves inside the wardrobes to minimise noise, or will that render them ineffective? 6. Access to the floor void above certain rooms is not possible without significant disruption. Two problematic ones are the WC and the utility. Both had normal extraction fans which extracted to the outside, until we built a two-storey side extension on that side of the the house. can easily poke a duct through the hole that was there for the fan into both rooms. The easier of the two is the utility, which had a wall-mounted extraction fan. We also moved the boiler flu a bit so have a spare hole to play with there too: I plan to use a standard plenum, with the ducts joining to it vertically from above so that the 125mm pipe sticks through one of these holes, and I can then put a standard valve on the other side. I will obviously fill up the rest of the hole so it is secure, and fix the plenum to teh wall somehow. Does that work? Or do I need a different plenum/valve combo for this? 7. The WC is harder. That has a ceiling mounted fan currently, like this: And again, I can relatively easily poke a 75mm duct through there to the room itself (you can see the opening tucked in there on the left hand side): But how do I fix the plenum if I cannot access the ceiling void? If the answer is "it's impossible" then I may need to block up that window and fit a wall-mounted valve as part of that, lust like in the utility. 7. Quality/costs of items. I cannot see any difference beteween say a standard plenum and a premium plenum. What am I missing, if anything? Same goes for standard vs premium valves. For the bedrooms I've assumed I would want the airflow dampened valves to minimise noise, but the airy ones are at least double that price. Are they twice as quiet? 8. I plan to run the ducting for the downstairs living room through a built-in wardrobe in the bedroom above as I have no other access to the ceiling void without tearing up finished rooms. The wardrobe has a plinth (say 15mm deep). My plan is to run the ducts down vertically and join to a straight plenum, into which I will insert a 350mm extension pipe. I will cut 125mm holes in the wardrobe plinth; the floorboards beneath; and finally the ceiling (lath and plaster, overboarded with plasterboard) and poke the extension pipe through that channel and attach a valve to the underside. Does this make sense or is there a better way to do it?

Hi everyone Serial refurbisher here. I am getting towards the end of my third project (which is my house) - complete renovation and extension of a 1930s detached house. I do leave the structural work to builders, but tend to do the internal work myself (splitting up the space into rooms; fitting kitchens etc). I also want to do a full self-build project in the future - it is something my parents did when I was a child in the 1990s and something I would love to do. In hindsight I should have just demolished my current house and rebuilt a high quality modern home, but never mind - next time! I have joined as this forum seems to be the only place to discuss MVHR. My house is not an obvious contender but with all of the work we've done (which includes a putting on a new roof; new windows throughout; extending on two sides of the house and re-rendering pretty much all of the existing walls, I am hoping that I will get some benefit. We would need a central extraction system anyway so I thought I'd go for MVHR to see if it does make a difference, but out of hope rather than expectation. I want to take advantage of the knowledge on here so I've signed up to ask some questions, and hopefully contribute a bit too.