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  • October 24, 2018 at 9:29 am #6175
    Nik Gregg
    Participant

    Hey All

    I get asked lots and lots for some detailed recommendations about what people should buy in regards to a bathroom extraction fan, what spec’s. I realise this depends on the size of bathroom, but……are there any guidelines that we can provide? eg: liters per second? power size?

    Cheers

    Nik

    October 25, 2018 at 9:02 am #6248
    Jo Wills
    Participant

    Hey Nik, 25l/s or 90 cm p/h for an intermittent bathroom fan is what’s recommended. Some of the three in one units say they can do over 90 cm p/h hour but my understanding is the fan units are too small and easily clogged for efficiency. And those units are never really going to be placed above the moisture source, so single fan units are the better choice.

    Apparently there are new/efficient three in one units on the market now though. Ian Mayes?

    October 25, 2018 at 9:09 am #6250
    Paul Hansen
    Participant

    SIMX is a common brand you would have seen and they have a nifty little pocket book on all their gear and specs. Easy to carry around as a reference as to what sort of moisture extractor they could look at

    October 29, 2018 at 5:12 am #6325
    Nik Gregg
    Participant

    Thanks Paul & Jo. I look at the SIMX booklet.

    I understand that the 25l/s is current building code, but this doesn’t really cut it? Something like 250m3 seemed better? Just wanted to see if there was anything formal around this.

    Cheers

    Nik

    October 29, 2018 at 9:38 am #6379
    Vicki Cowan
    Keymaster

    Hi Nik,
    I went back through notes I worked from for submission on Healthy Home Standards…

    For new installations Beacon recommends more powerful extractor fans in bathrooms / wet areas (e.g. 40 litres/s) using motion sensors with a delay timer and ensuring that the duct diameter and extract fan is 150mm. also want it to be well installed, minimum bends/kinks and estacting to the outside!
    Verney says he’s been talking to Steve McNeil @ BRANZ and he reckons if you specify the 150mm duct and fan grill this will help (obviously the fan should be sized for the room…)

    I received this advice from Richard P:
    Some minimum ventilation rates need to be specified. Our experience has been that many bathroom fans and kitchen extract systems are woefully undersized and do not perform adequately to achieve the desired outcome. Our recommended specification for bathrooms fans is a minimum airflow of 250m3/hour (equivalent to @ 70 litres/second).

    This might make a few people wade in – always welcome debate!
    V

    November 1, 2018 at 9:21 am #6452
    Nik Gregg
    Participant

    Awesome, thanks heaps V. Huge.

    November 2, 2018 at 10:43 am #6525
    Richard Popenhagen
    Participant

    I have played around a bit with different bathroom fans over the years and from my own personal experience going from some pretty average fans to much better, my ballpark recommendations are minimum size of 150mm (15cm) diameter including the ducting. Some fans, although appearing quite large, only have 100mm ducting on the exit.
    Re airflow, yes an absolute minimum airflow of 250m3/ hour, which equates to about 70 litres a second, however more is better.
    As an example I have attached some photos shot this winter in our bathroom. The first one is on exiting the shower the RH in the bathroom is 83%. Seven minutes later the fan has dropped the RH down to the magic 60% RH mark. Another five minutes later the RH is down to 48%, not bad for a bathroom on a cold winter’s morning!
    This is where I need to fess up, our current bathroom fan is very powerful, although still only 150mm diameter its rated specification is 597m3/ hour (166 litres per second). It is so powerful that if you don’t crack open the bathroom window, we struggle to shut the bathroom door against the air pressure.
    The point I want to reinforce is that you are better off with a very powerful bathroom fan, where you can reduce the moisture load quickly, rather than an undersized fan often which won’t have reduced the moisture adequately even after 40 minutes plus running time. Do it hard and do it FAST!
    Cheers Richard

    November 2, 2018 at 10:49 am #6527
    Richard Popenhagen
    Participant

    Ops, file size was too large, have reattached as smaller files

    Attachments:
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    November 9, 2018 at 6:10 am #6603
    Nik Gregg
    Participant

    Brilliant Richard, thanks very much – very useful.

    Nik

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