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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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Ventilation: Extractor fan or heat recovery?

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    Basic extractor fan or something with heat recovery best when you've got a heat pump?

    Our downstairs shower room extractor fan died a few months ago but we now seeing a possible beginnings of a damp issue so it's time to put a new one in. Would people recommend a simple basic one or something more complex with heat recovery? The old one was a basic one, turned on when light switch to room was turned on and then stayed on for a few mins after light turned off.

    Situation: air source heat pump, ~1900 build solid wall house, radiators. South east Scotland. Wet room is approx 3 x 4m and has shower, sink, toilet and heated towel rail. Isn't actually used for showering that much since it's an electric shower and we prefer to use the mixer upstairs. The room is used for hanging wet swimming and watersports kit to dry.

    We're not super at DIY so would prob get someone to install for us (in case that makes a difference to recommendation).

    Thanks in advance for advice.
  2.  
    Our heat recovery fans are very good for drying washing because they bring in a constant flow of dried air (Vent axia Tempra).

    On boost mode it sounds like a trad bathroom fan whereas more modern bathroom fans are surprisingly quiet. Newer dMHRV models have been launched that are quieter.

    Easy to fit, just slides into the hole left by the previous fan, but use electrician to connect the power supply.
    • CommentAuthortony
    • CommentTimeFeb 18th 2024
     
    I hate extractor fans! They take air from indoors that has been warmed and cost money to do that them blow it away to outside! The opposite of a sustainable action akin to burning money.
  4.  
    Thanks for the advice folks
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      CommentAuthorfostertom
    • CommentTimeFeb 19th 2024 edited
     
    Def don't fit a recovery fan inside a bathroom. Even if super-efficient (unlikely at the lowish cost of such items, compared to proper MVHR), by definition the incoming air is (slightly or a lot) cooler than the outgoing room air, and it's moving at velocity, so feels like a cold draught esp to a wet naked body. Been caught that way - intolerable - the fan had to be taken out. Whether with a simple extract fan, or MVHR, bathroom air must be drawn into the bathroom from the heated house, before being extracted. No vent input direct into the bathroom.
    • CommentAuthorRobL
    • CommentTimeFeb 19th 2024
     
    Years ago we had a single room vent axia HR25 in our bathroom. It was pretty good at keeping down humidity - left on all the time on a low setting and had a humidity meter to auto boost when needed. Crucially don't place too close to a shower, as there'll be a cold draught coming out of it. We considered this, and blocked up the original fan hole over the bath, drilled a new hole away from the bath for just this reason.
    After keeping it for 5 years, the manufacturers "whisper quiet" was optimistic - I could hear it 7metres away at night even on low. In freezing conditions it developed a nasty rattle, something to do with ice I expect. We part ex. it for a nice bottle of red wine in the end ... I now consider this sort of fan as a gateway device into full fledged mvhr that we have, which is just hands down better.
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      CommentAuthorfostertom
    • CommentTimeFeb 19th 2024
     
    The recovery fan I mentioned above was indeed well away from wet-body area but still felt like a cold draught.
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      CommentAuthordjh
    • CommentTimeFeb 19th 2024
     
    I think it all depends on the air currents in the particular room, which in turn depends on the exact shape of the room and fittings, position of doors and how much open they are etc etc

    I turn the MVHR down when I have a shower, rather than up, precisely because of this draught issue. My wife doesn't care either way. So it also depends on the individuals and their habits.
  9.  
    Posted By: tonyI hate extractor fans!


    I thought you liked the SVARA
    • CommentAuthortony
    • CommentTimeFeb 19th 2024
     
    They are the least worst if one is needed
    • CommentAuthorMike1
    • CommentTimeFeb 19th 2024
     
    For a shower room I agree that you don't want to introduce outside air. Last time I had the problem I chose an Airflow Icon Eco for the 'iris' shutter, which worked very well in minimizing airloss and drafts when not working, as well as avoiding the noise of a flapping duct shutter.
  12.  
    Posted By: Mike1Airflow Icon Eco for the 'iris' shutter,


    I also like these and will be getting one to replace the SVARA that I fitted in the upstairs bathroom, it's annoying me because I also fitted a

    Posted By: Mike1flapping duct shutter.


    which currently has a pair of socks stuffed in the tube so that I can sleep at night.

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