Home  5  Books  5  GBEzine  5  News  5  HelpDesk  5  Register  5  GreenBuilding.co.uk
Not signed in (Sign In)


Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.

Buy individually or both books together. Delivery is free!

powered by Surfing Waves

Vanilla 1.0.3 is a product of Lussumo. More Information: Documentation, Community Support.

Welcome to new Forum Visitors
Join the forum now and benefit from discussions with thousands of other green building fans and discounts on Green Building Press publications: Apply now.

    Hi everyone,

    I'm looking to DIY install our MVHR system and have it professionally commissioned and balanced. I also had the though that I would design the ducting, but I've just spent a VERY frustrating couple of hours trying to make some headway.

    I've now come to the conclusion that visualising ducting in 3D is not my strong point.

    Are there companies/individuals that will design a ducting system without requiring me to buy all their bits and bobs? I already have the unit and was planning on buying all the other materials myself.Any idea of costs? Had a scary quote for PHPP modelling, so don't want to go down that road again!

    Suggestions of people who actually know what they're talking about would be much appreciated.

    Most of the MVHR suppliers I've come across will design for free.

    Airflow did a very detailed quote for me with flow rates, 3D images and plans. They don't even supply direct - you then need to send their 'part list' to one of their retailers for a quote. I can't see any reason you couldn't swap out various parts (including the MVHR unit itself) for other manufacturers (which I intend to do - their own pre insulated ducting is horrifically expensive compared to others)
    Simon - thanks for your comments on all my threads! I have sent a quote request off to Airflow, so we'll see what they come back with. Did you think your design was quite sensible or did you have to adjust it a bit?

    I have already got the Vent Axia Sentinel Kinetic Plus B unit - too good a price to resist, so hopefully it will be OK.
    Currently researching ducting, there's so many more options than I thought were possible!

    Design seemed fine - I asked a few questions on here and all the things that puzzled me turned out to be best practice. My only real concern was the use of flexible ducts for the main in/out for fresh/waste air. I'm going to replace that with rigid duct from another supplier
    Excellent, that's really good to hear. I was dreading messing it up by doing it myself!

    Thanks for the tip.
    • CommentTimeApr 19th 2014

    Also, try Vent-Tek in Dorset. They're independent and extremely knowledgeable and helpful.
    • CommentAuthorAMG
    • CommentTimeJun 21st 2014
    Getting myself slightly confused with the design principles -

    1. Does every room need a supply?
    2. Does every room need an extract? Or do you
    extract from wet areas only (bathroom/toilet and kitchen)?

    How do you decide where silencers go?

    I have sent my drawings to a number of companies but non will show me the design. Instead they just give single quote. Happy to pay for it or to design it myself (with help) and then order the components?
    • CommentAuthorEd Davies
    • CommentTimeJun 21st 2014
    Usual thing is supply to living rooms and bedrooms, extract from kitchens, bath/shower rooms and toilets. Utility rooms are usually extract, I think.
    • CommentAuthorAMG
    • CommentTimeJun 21st 2014
    What happens in an air tight(ish) house and having only extracts in kitchen and bathroom? Would those extracts be powerful enough to draw air from bedrooms/living room via ventilation spaces under doors?

    I suppose it must as everyone does comment in the freshness and air quality after installing mvhr.
    • CommentAuthorEd Davies
    • CommentTimeJun 21st 2014
    Yes, gaps under doors are plenty. Some put small grills at the bottom of doors but most find it unnecessary. I suppose it would be silly to have very snug fitting doors.
    • CommentAuthorGotanewlife
    • CommentTimeJun 21st 2014 edited
    When I did mine I made sure my gaps under doors were at least the same area as my inlet pipes.

    And you must also have inlets not just extracts as you perhaps didn't mean to say above :wink:
    • CommentAuthorArchmoco
    • CommentTimeJun 23rd 2014
    Supply in habitable rooms extract utility, wc, bathroom. I've seen the kitchen extract through a grease filter, but I kept mine as standard extract directly to the outside. If you have a separate room for an accumulator tank stick an extract in there too as the excess heat will be good during winter.

    You want the unit as central as possible and ensure good access for changing filters. I went with a Beam Acxo and very happy with it, it's rotary so technically not as efficient as plate ones, but it's rare if my efficient drops below 90%. With rotary you don't need a condensation drain. Also,there can be a bit of noise from the units so don't stick it directly over a bedroom or near the TV
    • CommentTimeJun 25th 2014
    Posted By: divorcingjackAre there companies/individuals that will design a ducting system without requiring me to buy all their bits and bobs? I already have the unit and was planning on buying all the other materials myself.

    Yes but ...

    The various ducting systems don't all have the same design rules. So if you get a design for one ducting system, you can't just apply it to a competitor's system.

    We just bought a semi-rigid ducting system. I haven't fitted it yet but I'll whisper my experience so far.
    • CommentTimeJun 25th 2014
    Posted By: ArchmocoI've seen the kitchen extract through a grease filter, but I kept mine as standard extract directly to the outside

    That depends on your target efficiency, of course. There's a lot of valuable heat produced in a kitchen that is worth recovering for a very low-energy house.

    You want the unit as central as possible

    It's true that a centralised unit or distribution manifold can minimise the overall duct length. But to minimise the heat loss/gain from the external supply and exhaust you want the insulated ducts that lead to the wall/roof terminals to be as short as possible. So with wall terminals such as we have, it's apparently best to have the unit next to an external wall.
    • CommentAuthorTriassic
    • CommentTimeJul 21st 2014 edited
    I'm also starting to design the MVHR system and as our house has a separate wing containing the lounge, with bedroom and en-suite above. Could I use a separate small mvhr system just for that part of the house?

    Just a thought, the lounge has a wood burning stove, how does that affect the design?
    • CommentAuthorGotanewlife
    • CommentTimeJul 21st 2014 edited
    Posted By: TriassicCould I use a separate small mvhr system just for that part of the house?
    Yes definitely but be alert for those units that don't have balanced flow (ie same volume of air in as out) - it probably will not be an issue but is factor that ought to at least be considered if you go for more than one unit.
    • CommentAuthorbarney
    • CommentTimeJul 22nd 2014
    WRT to the woodburner, and presuming the Woodburner unit doesn't have a dedicated external air supply then make sure that you have an excess of air on the supply side compared to the extract side to provide both combustion air and to avoid negative pressure in the space and thus spilling of the woodburner.

    Do a combustion test on the WB when the room is finished and with the MVHR running normally

    If it has a boost capability, put a CO sensor in parallel to force boost if CO is detected


    • CommentAuthorfinny
    • CommentTimeJul 24th 2014
    If your woodburner is not room-sealed you will need to test the draft pressure at the flue with the unit on boost, not normal. You need 12 pascals. I don't like the idea of boosting supply air if CO levels get high. You need an alarm to get you out ASAP. Then you need to redesign your system so that it works safely.
    • CommentAuthorShevek
    • CommentTimeJul 24th 2014
    Have you all considered Ventive passive ventilation with heat recovery? Quite easy to install and not much design to it, apart from making sure the ducts running as straight as possible from the roof down to the room.
Add your comments

    Username Password
  • Format comments as
The Ecobuilding Buzz
Site Map    |   Home    |   View Cart    |   Pressroom   |   Business   |   Links   

© Green Building Press