Why a Timer Fan is More Recommended than a Fan with Humidistat Module

Why a Timer Fan is More Recommended than a Fan with Humidistat Module - picture of an Envirovent Fan with Humidistat operating in the bathroomWe have recently encountered this problem and there was a question from many of our customers: do I need a bathroom fan with humidistat function, or will a fan with timer do?

You could say that it all depends on what you need the fan for, what are the conditions the bathroom is in, what is the weather, what you use the bathroom for, etc.

But in general, for the majority of people, a bathroom fan with timer is more recommended than a fan with humidistat. Unless there are special conditions with extreme humidity being constantly in the bathroom, all you need is a timer fan. Let us explain why.

How does a Humidistat Fan Work?

What does this “humidistat module” do in a ventilation fan? Whether it is from Manrose, Vent-Axia, Envirovent, or Airflow, most of the bathroom fans come both in a basic version and in the version with timer, with humidistat, or even with timer and humidistat together (of course, the price is also higher).

A humidistat is a sensor within a certain module in the fan that detects the level of humidity in the air, and then switches ON or OFF the fan. The humidistat can be set and adjusted as needed, so that when there’s a lot of humidity in the air, the fan will automatically be ON until the humidity is eliminated.

How does a Timer Fan Work?

A timer bathroom fan is pretty straightforward and simple: you can set the time delay for the fan to continue to run once someone has used the bathroom and left (switching off the light).

In other words, the fan will continue running for a period of 30 seconds – 3-4minutes (according to your settings) after someone has taken a shower or has used the bathroom for more than 2-3 minutes.

This is the most common use of the bathroom fan, and most bathrooms are not completely and properly ventilated unless a ventilation fan with timer is installed.

Why are the Timer Fans Better?

Why are the Timer Fans Better? In the picture: an Airflow Quietair 100 with a humidistat sensor
Airflow Quietair 100 with a humidistat sensor incorporated

Again, we don’t prefer or replace a humidistat fan with a timer fan, but in general use people rather need a bathroom fan with timer than one with humidistat.

If your bathroom is in an area with a lot of humidity, it is good to get a humidity timer and set it on not-so-sensitive setting. If the humidity level in your bathroom is always up and ventilation is needed all the time, a fan with humidistat is a must.

But if you don’t have huge problems with the humidity and all you need is a fan that would ventilate the air and make sure you have fresh air while the humidity and odours are eliminated a regular timer fan is the best solution.

If you are planning to leave your house for a while and you know that the humidity can be up while away, you definitely need a bathroom fan with humidistat. But if you’re at home or your family is regularly using the bathroom during the day, you don’t need a humidstat fan but a fan with timer.

Tip: Don’t Fiddle Too Much with the Humidistat

A humidistat is a very sensitive module within the fan, and not everyone understands how it works. The mere fact that you see that the humidistat doesn’t turn the fan ON when you think that the humidity is high doesn’t mean that you need to regulate it and adjust it all the time.

Unless there are special humidity conditions in the bathroom, setting your humidistat on 60% or so should solve all the problems (see the manufacturer’s specs and ask your electrician about more precise advice).

But tinkering with the humidistat may cause it to be damaged – you simply have to “trust it”, that it will work whenever the level of humidity is higher!

Do You have a Similar Experience?

Did you install a humidistat fan? What is your experience with it? Maybe you want to share something you’ve learned while setting up, using, maintaining, and taking care of your humidstat fan (or timer fan) – please do so in the comments.

You can read more technical details on how the humidstat works here, here, and here. To purchase bathroom fans with timer, please visit the Ventilation Systems at Sparks Direct.

7 comments

  1. EnviroVent
    All bathroom fans are basically there for one reason and that is to control the humidity levels within the bathroom, for comfort, health and to protect the fabric of the build.
    Bathrooms produce humidity constantly as there is standing water in the toilet and sink and of course wet surfaces and fabrics. The situation is exacerbated at night when the cool evenings cause the relative humidity levels to rise.
    Timer functions and humidity sensing (as fitted to our Silent Range of fans) are both useful additional features depending on the needs of the user, but for the very best in humidity control Envirovent would recommend a continuous running fan such as our ECO dMEV Fan which extracts continuously at a low/ trickle rate. This fan ensures the very best environment at all times with 5 adjustable extract rates giving guaranteed airflows.
    For more information on this and other products please visit our website, http://www.envirovent-trade.com/eco-dmev.php or call EnviroVent on 0845 27 27 810.

  2. Vent Axia say that “a humidity controlled fan is looking at the ambient humidity level to activate/deactivate the fan, and so it is important to remember that normal ambient humidity levels on a given day can trigger a humidity fan in just the same way as humidity generated by steam from the bath/shower room or Kitchen if the humidity level rises above the set-point.”

    Elsewhere it is suggested that 60% is a sensible humidity level for comfort and others suggest the optimum level for human beings is 55%. Today the humidity level where I live is 69% and the historic average for the month is 80%. How then is it possible for a humidistat controlled fan to operate effectively?

  3. The headline says:
    Why a Timer is more recommended than a Humidistat.

    Sorry, but I don’t see any reasons – juist two assertions:
    i) ” in general use people rather need a bathroom fan with timer than one with humidistat.”
    (Why ? The next sentence is about a Humidistat helping with higher humidity (e.g. when bathing)

    ii) “But if you don’t have huge problems with the humidity and all you need is a fan that would ventilate the air and make sure you have fresh air while the humidity and odours are eliminated a regular timer fan is the best solution.”

    This discounts humidity – which is the primary reason given in Bldg Regs.
    So that leaves odours. Surely this would apply only to a toilet with no windows. (Bldg Regs do not require vents for small toilets – if an opening window is there)

    The second phrase mentions a Timer only vent. What if the Humidistat switches on with the light anyway ?

    iii) “But if you’re at home or your family is regularly using the bathroom during the day, you don’t need a humidstat fan but a fan with timer.”
    Why ? “Regular use” would imply a lot of door opening and closing – so “activated” air circulation

    (p.s. I’m not a Humidistat Salesman – I just can’t see any substantive “reasons” here )

    1. Very much a case of horses for courses. In a bathroom with no chance of natural ventilation i.e. no window a timer fan that operates with the light is just fine although I’d query the 3-4minute delay suggested, for most bathrooms at least 10 minutes would seem better. In other cases where the light would not always be required, I would always suggest a low constant flow and low wattage unit with a Humidistat boost set to around 70% RH. The constant low flow would ensure that the room when not being used can draw through air from the rest of the house and keep the room temperature at a fairly steady level to minimise condensation in the first place.

  4. Problem with this plan is when a guest // tenant uses the Bathroom in the day time. Most fans are connected to the lighting thus if you have a shower when it’s bright outside you’re less likely to turn the light on, this means the fan fails to operate and the room becomes very damp very quickly.

    If you have a humidity sensor you ensure the fan operates, thus a dual fan is normally best.

  5. With teenagers, or in rental situations, moisture-activated fan switches are better than regular timers because regular timers are often ignored by users. What works well for me is incorporating a hot water pipe solenoid valve with the timer. In other words, no hot water in shower until user activates fan timer. Bye bye black mould and steam dripping from ceiling and walls.

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