ToughButterCup Posted April 20, 2017 Share Posted April 20, 2017 The harsh interpretation is that we cocked up. The kinder version is that the design evolved: in a haphazard way yes, but it evolved, evolved I tell you! The question: how do I arrange the MVHR ducting between two buildings? The Answer: dig a trench, line it with concrete, and shove the pipes in with as much insulation in as you can (wrap it it in some spare EPS300?) The excuses first: We came too late to ebuild to start our planning with passivhaus in mind. It took us a full year to realise the implications that choosing MVHR would have. It took a further few months to realise that we needed to site the plant room in our piggery. Have a look at this. The Piggery (the plant room) is on the right. There are two six inch ducts and a spare ready for the MVHR unit. The house slab (on the left) shows the ducts entering the heated envelope. The Piggery will also be heated to PH standards. Each of the ducts has two 45 rest-bends underground and have been capped off - until I stop sucking my teeth wondering how to bodge this one. Problem: how to duct the in and out airflows underground without causing condensation My guess at an answer is something along the lines: run a concrete-lined trench between the two buildings to contain the pipes. Lag the Hell out of them. Make sure I can inspect the trench to check for water ingress, and make sure I can drain any condensate out of the MVHR pipes themselves. Maybe even make sure I can visually inspect the inside of the MVHR pipes? My fingertips say that this last bit is desirable, but probably not essential. My worry is that we will have to insulate the pipes as they come out of the trench and return to each building, and that will have to be insulated just as well as the rest of the pipe. In other words, the trench will be the easy bit. I can just see myself under the foundations lagging the pipes right up to the bottom of the strip foundation. Still, if I can't take a joke, I shouldn't have started this should I? Link to comment Share on other sites More sharing options...
SteamyTea Posted April 20, 2017 Share Posted April 20, 2017 12 minutes ago, recoveringacademic said: The question: how do I arrange the MVHR ducting between two buildings? Why not separate units for each building? Link to comment Share on other sites More sharing options...
jack Posted April 20, 2017 Share Posted April 20, 2017 Do you absolutely need to connect it to the main MVHR unit? Having long U-shaped ducts seems to be begging for problems. I know you'll be insulating them, but I can't help but think of that Belgian (I think) house that was condemned due to infected earth pre-heat tubes following moisture build-up. At the least, you'll need to consider some sort of sump and drain arrangement (again, I think). My personal preference would be to find a way to ventilate it separately. Is it small enough that one of those in-wall counterflow units would work? Or the Viking House fine wire unit? Link to comment Share on other sites More sharing options...
Ferdinand Posted April 20, 2017 Share Posted April 20, 2017 (edited) What happens in the gap? Can you run the pipe above ground inside something like a potting bench or a sitting area or a raised garden feature such as a terrace or a double fence? Edited April 20, 2017 by Ferdinand Link to comment Share on other sites More sharing options...
ToughButterCup Posted April 20, 2017 Author Share Posted April 20, 2017 @SteamyTea, the house doesn't have room for the MVHR unit - well it does, but it takes up too much space overall. @jack, is this what you mean? @Ferdinand, [gap] nothing much for a while: bike storage, concreted base for an outside work area. But my cunning long term plan is to link the two buildings (four piles already exist between both ends of the piggery and the house so we can link the two buildings) 20 minutes ago, Ferdinand said: [...] Can you run the pipe above ground inside something like a potting bench or a sitting area or a raised garden feature such as a terrace or a double fence? Hmmmmmm. Ian Link to comment Share on other sites More sharing options...
SteamyTea Posted April 20, 2017 Share Posted April 20, 2017 'Not even a small, though the wall one (or several)?' Like.....? Link to comment Share on other sites More sharing options...
jamiehamy Posted April 20, 2017 Share Posted April 20, 2017 Slightly confused - if the pipe is 6inch (150mm), and the duct is going to be min 125mm - and that type of duct is rigid - how do you get the duct through? Or are you using the 6inch pipe as the duct? Personally, I would revisit putting the unit in the house - I would never be happy running air ducts outside underground - aside from the condensation risk, you'll likely never stop worrying about it or tying yourself up in knots trying to find a workable long term solution that doesn't having you checking the duct every 3 months. I hear what you say about room but anything is possible, esp at this stage. Link to comment Share on other sites More sharing options...
ToughButterCup Posted April 20, 2017 Author Share Posted April 20, 2017 5 minutes ago, jamiehamy said: [...] I hear what you say about room but anything is possible, esp at this stage. I need to go round the MVHR 'desert' for another 40 years don't I? Ian Link to comment Share on other sites More sharing options...
jamiehamy Posted April 20, 2017 Share Posted April 20, 2017 Just now, recoveringacademic said: I need to go round the MVHR 'desert' for another 40 years don't I? Ian Yup! Or just decide a location for it i the house (cupboard or whatever), run all the ducts there and worry about how they'll all fit into the manifold/unit when the time comes.. Okay, it's not that simple, I know but I know if it was me, having air ducts running outside underground would have me wondering all the time. And if it would worry me, I suspect it would worry you Link to comment Share on other sites More sharing options...
jack Posted April 20, 2017 Share Posted April 20, 2017 22 minutes ago, recoveringacademic said: @jack, is this what you mean? Yes, that's the one. There are smaller through-wall units like this one. I'm sure I've seen counterflow exchangers that are more like conventional through-wall extractor fans, but I can't seem to find one right now. Efficiency is low, but they're cheap, and easy to get rid of if and when you ultimately link the buildings and start using the MVHR in the currently separate room. Link to comment Share on other sites More sharing options...
ToughButterCup Posted April 20, 2017 Author Share Posted April 20, 2017 4 minutes ago, jamiehamy said: [...]. And if it would worry me, I suspect it would worry you It's as bad as having children. Lying awake at night waiting for the front door to slam - the reassuring door slam of the self-obsessed teen - at least that puts an end to the worry. Sometimes. Link to comment Share on other sites More sharing options...
ragg987 Posted April 20, 2017 Share Posted April 20, 2017 (edited) Just to check - the MVHR itself is in the piggery, so the ducts connecting the 2 buildings would be be at a more stable and relatively constant temperature flow at around 16 to 20C. Surely the risk of condensation is reduced significantly IF you insulate the ducts underground? In my install the ducts after the MVHR have shown no issues at all (admittedly they are both inside the thermal envelope), but the cold supply from outside the building to the MVHR has been problematic and I ended up cutting out the supplied foil-backed fibreglass insulation and fitting in Armaflex - great stuff, glued to the duct so a much better solution. Havea look at the Armacell website - they offer external-grade insulation that might offer an answer. Edited April 20, 2017 by ragg987 fibreglass for clarity Link to comment Share on other sites More sharing options...
SteamyTea Posted April 20, 2017 Share Posted April 20, 2017 Can you build an outside 'cupboard' to house the unit(s)? Treat is as a novel 'feature', rather than an industrial fitment. Link to comment Share on other sites More sharing options...
ToughButterCup Posted April 20, 2017 Author Share Posted April 20, 2017 @ragg987, you have just mapped the next part of my impending 40 year traipse round the MVHR desert. Thanks. '...cutting out the supplied foil-backed fibre insulation and fitting in Armaflex ...' Ian Link to comment Share on other sites More sharing options...
ToughButterCup Posted April 20, 2017 Author Share Posted April 20, 2017 Just now, SteamyTea said: Can you build an outside 'cupboard' to house the unit(s)? Treat is as a novel 'feature', rather than an industrial fitment. Yes, I think I could @SteamyTea, in the same way as houses have external ASHPs. Link to comment Share on other sites More sharing options...
ragg987 Posted April 20, 2017 Share Posted April 20, 2017 Glad I could help! I'm sure we can help map the next 40 years too. Link to comment Share on other sites More sharing options...
PeterW Posted April 20, 2017 Share Posted April 20, 2017 1 minute ago, recoveringacademic said: @ragg987, you have just mapped the next part of my impending 40 year traipse round the MVHR desert. Thanks. '...cutting out the supplied foil-backed fibre insulation and fitting in Armaflex ...' Ian There shouldn't really be fibre / foil in modern small units as polymer insulation is far more efficient than fibre per mm. There are some MVHR units that will fit in a kitchen cupboard so there should be room in the utility.... Link to comment Share on other sites More sharing options...
SteamyTea Posted April 20, 2017 Share Posted April 20, 2017 (edited) Yes, I think I could (said Ian) Except it can be totally boxed in, does not need a large open surface or two. I would think that the first person to suggest a balcony got laughed at. Why would you build one when you can have an extra room Edited April 20, 2017 by SteamyTea Link to comment Share on other sites More sharing options...
PeterW Posted April 20, 2017 Share Posted April 20, 2017 This is only 298mm deep and 600mm wide so would fit into a "normal" kitchen wall cabinet space http://www.nuaire.co.uk/our-products/catalogue/residential/heat-recovery-(mvhr)/mrxbox95ab-wm1/ Or even smaller - will fit inside a kitchen cabinet (and a good price too !) http://www.fantronix.com/acatalog/Polypipe-Silavent-HRX-Heat-Recovery-Unit-MVHR---Whole-House.html Link to comment Share on other sites More sharing options...
Construction Channel Posted April 20, 2017 Share Posted April 20, 2017 Could you not link the two buildings with just a canopy? (2 steels and a small pitched roof) then run the pipes at high level and insulate the hell out of them. Then just use the ground ducts for the wires? Link to comment Share on other sites More sharing options...
ToughButterCup Posted April 20, 2017 Author Share Posted April 20, 2017 14 minutes ago, Construction Channel said: Could you not link the two buildings with just a canopy? [...] It's the obvious answer, but PD rights have been withdrawn (as is common). Link to comment Share on other sites More sharing options...
PeterW Posted April 20, 2017 Share Posted April 20, 2017 I'm still erring on the side of a utility room mounted unit here !! Check with Gary @bpc ventilation as I'm sure he will have an answer Link to comment Share on other sites More sharing options...
jack Posted April 20, 2017 Share Posted April 20, 2017 I doubt you'd get by on a non-material amendment, but could you apply for a minor material amendment? Link to comment Share on other sites More sharing options...
ragg987 Posted April 20, 2017 Share Posted April 20, 2017 59 minutes ago, PeterW said: There shouldn't really be fibre / foil in modern small units as polymer insulation is far more efficient than fibre per mm. I did not mean inside the unit, but the main supply duct from outside. Link to comment Share on other sites More sharing options...
PeterW Posted April 20, 2017 Share Posted April 20, 2017 2 minutes ago, ragg987 said: I did not mean inside the unit, but the main supply duct from outside. I'm surprised that is fibre too - usually used on process / steam pipes as it is suitable for over 100c surface temperature. Link to comment Share on other sites More sharing options...
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