If you're not sure which to choose call 01892-600121 for advice

You can also see the ventilation guide for information on which fans and installation guidance.

Humidstat fans have a sensor in them which absorbs moisture from the air stream of the fan. The sensor detects when moisture levels rise to a set level and at this point the fan is either switched 'on' or to higher 'boost' speed when the pre-set moisture threshold is reached. The problem with this is that in the UK normal background levels of humidity vary between 30% - 90% from summer to winter – a 60% difference. So, if your fan is set to activate to come on or to boost at any point between 30 – 90% it can activate when you may not want it to – i.e. a humid summers night when you are sleeping, or, if set too low, will not activate when you do want it too.

The problem described above occurs with traditional basic humidity sensing controls. These have been used for many years and are the most common feature in the majority of humidity sensing fans sold today which, whilst functional, lack the ability to be able to be controlled 'intelligently' with modern 'smart' technology. Alternative technology is available which uses modern sensing which, unlike standard fans, do not have a fixed point for on/off and work by constantly measuring the natural humidity level of your room and not react. The fan notices these natural variations and it does not react. Instead, the fan is programmed to detect man-made spikes in humidity caused by showering, bathing or cooking and only then increase to boost speed.

Greenwood have developed this technology and have registered the name HumidiSMART®. So if you want to make sure that ventilation is delivered (to help prevent mould and mildew and keep the room fresh) only when it is absolutely needed –and not when you don't, look for the HumidiSmart name on the product details (link to the humidity page). Sweet dreams zzzzzzzzzzzzzzzzz.