Jolo

We had a new front door installed earlier this year -- lovely 65mm thick thing with insulation inside, triple glazing in the frame as the side and above. A big improvement over the rotten old plank of wood with single-glazed windows we had before! One thing we pondered was the letter box. One option was to not have a letter box in the door, but instead have a lockable letter box outside. We decided against this partly because it didn't feel very secure (especially if we're away) and also because to get the post we'd have to open the door fully and go outside to open the external box -- which, while brief, would probably let in more cold winter air than a well-sealed letterbox in the door would! (Also didn't fancy having to go outside in my dressing gown every morning.) So we opted instead for a letterbox in the door, which we discovered has the strongest springs known to mankind. It really slaps itself shut! But this led to a problem, our postie will lift the outside flap, and push the letters in -- but the post isn't strong enough to open the inside flap, so the letters instead get left trapped dangling from the outside flap for anyone to take. (Call me paranoid...) While visiting friends earlier this year, I noticed that they had a new door too -- with the exact same letterbox! I asked them if they'd had problems with the postie leaving letters dangling and sure enough they had. So it must be a common letterbox that's causing issues wherever it's installed! As our new door was fitted in the spring, my temporary solution was just to remove the internal plate. But now that October is here I'm pondering better solutions. One option is to buy one of those letterboxes that has thick flaps (!) with insulation in them, but I wonder if we'll still have the problem with dangling letters. Another option is to add a post catcher on the inside, which I could even make myself and insulate well enough. (A third option is to tell the postie off, this is what our friends in England did! But I suspect the problem would just occur again every time a new postie did this route.) So, before I break out the wood and unfold the workbench, are there any ideas about how best to mitigate my letterbox problem? Thanks in advance!

Except when cooking/showering/toiletting, we generally keep it on the lowest setting which right now is 80m3/h. Our house is 200m3, so I think that 80m3/h might be a little higher than most people on here seem to have theirs set (I read a lot that people set the normal rate to 0.3ach, which for us would be 65m3/h). I think it's a bit higher because when we set it up in the summer, the house was stuffier and warmer, so wanted as much night-air bypass ventilation as we could. I've actually added a strange thing but one which I'm really happy with -- a night-time boost lever for the bedroom. It's a three-way valve which we can move so that overnight the bedroom gets air that would normally be going to the (empty) living room, doubling the output without increasing the fan speed. So this might mean that we can turn the normal speed down to 65m3/h. We do definitely need to get a CO2 monitor, this has been on my list for ages! (Right now we're dealing with a floor that's been bodged, the DIY is never done, even when you hire professionals...)

I also experienced a droning noise, but after buying a rectangular attenuator from Lindab (thanks to your photos and advice here @Nick Laslett and @Nickfromwales!) which didn't stop it, I determined that it wasn't coming from the main unit, but was being generated within the green ribbed Ubbink Air Excellent ducting. So for the bedroom I added a 1m flexible attenuator at the end, just before the vent, and it works great. To avoid adding too much more static pressure I went for one with a 100mm internal diameter (larger than the 75mm internal diameter of the ducting). It works really well, even on boost it's barely audible and at night we don't have it that high anyway, so it's totally silent. I since added another to one of the living room vents, and it's worked great there too. While this does work, is there anything I'm missing? Is there a reason I've never seen this recommended anywhere?

Great minds think alike, eh! I can't claim credit for the idea though, I saw it on a YouTube video where a guy in the US was replacing his MVHR unit and he happened to have a pre-filter box with a diagonal filter, which he also explained. The cloth you've used as a filter is interesting... I might try something like that instead of buying more G3 material. Though the stuff that my filter box came with is so thin, I doubt it causes too much pressure drop, the F7 in the main unit probably causes far more. Your box now has some serious insulation on it!!

Thanks for the additional info, @Mike! Your advice about the correct sealing rings makes sense, although with the Vent-Axia vent adaptors the ring is inside the adaptor already, and is the same cross-section as the duct, which presses up tight against it, the ribs on the duct clipping into plastic hooks inside the mouth of the adaptor. That's probably the exception though, as everything else I've seen has some sort of ring that goes around the duct. Do you remember which brands you mixed, and in what way?

Hi all, New member here. I read this thread with interest, as my new MVHR F7 filter became black with muck and flies in just a few weeks (ugh). After failing to find an insulated box for sale anywhere (I'd have thought they'd be popular!), I ended up buying a metal filter box from an online retailer (actually ended up with two, silly story) and, as expected, it became misty with condensation as soon as the outside temperature dropped. So thanks to @Nick Laslett's advice I bought a square metre of 19mm-thick Armaflex AF self-adhesive insulation and covered the box in that. It's not pretty but it does work really well, the outside of the insulation doesn't feel cold at all, even though the metal box inside is. One question I had for @Russdl while looking at the photo of the grime-covered filter was, have you considered putting it in the box at 45 degrees? From the photo it looks like nearly all the air flow across the mesh is through a circle which is against the duct that's behind it. But with the mesh at 45 degrees you'd have a much larger air flow surface area (the diagonal of the side of the box, by the width of the box) which should mean less pressure drop, and a longer time before it becomes clogged. (Just my 2p's worth - I wish I had space for such a big pre-filter!)

Thank you, Mike!

I was very interested in this topic too, as I wanted to mix manufacturers in our MVHR self-install (we went all-Ubbink, except for two through-wall vents, which Ubbink don't make). So we successfully connected Ubbink 90mm (75mm internal) semi-flex ribbed green ducting to Vent-Axia UniflexPlus valve adaptors. The Ubbink duct just clicks into the Vent-Axia adaptor without problems, and there's no sign of air leakage. The end of the duct presses up tightly against the foam inserts inside the valve adaptor, which is what I assume prevents leakage. I strongly suspect that other brands are also interchangeable. There's a company here in the Netherlands which sells their own brand of ducting and fittings, but they look identical to the ones sold by Blauberg. (From the searching I did, I think they're actually made by a company in Ukraine.) Anyway, this Dutch firm claims compatibility with Ubbink, Heatpex, Hybalans, Zehnder, Vent-Axia, and Burgerhout, which is a good list of manufacturers! So I reckon it's likely that the ribbed semi-flex ducting from one brand is compatible with another brand's valve adaptors / plenums / etc.

I grew up in England, but now live in the Netherlands, where my partner and I have a fixer-upper from the 1960s. One big task we recently completed was installing MVHR (previously it only had natural ventilation, which let in sounds in summer and cold in winter). This forum was a great resource during planning and installation, so I would like to thank everyone who has written here on that subject! Although I speak Dutch, and there are some great forums here which cover these same topics, it's much easier for me to quickly read posts in English. And MVHR is one thing that's not so different between countries, as the system we bought is one that's available in the UK too. I joined originally so I could answer a question in a thread which I would have found greatly useful (about compatibility between different brands semi-flex ducting and fittings), but there have also been times when I needed a sanity-check or could add my 2p's worth to a thread. So here I am!