When we fit extractors in bathrooms we either nip down to our local DIY store or we rely on our builders to get an extractor. This effectively means that we get the cheapest and most common extractors on the market. These are generally controlled by the light and if we are lucky we get a timed extractor. However, there are a number of other choices that might just provide you with a better solution for your home.
The main overlooked choice is an Humidity Controlled extractor. These are slightly more expensive (but not by much) than standard extractors, but they do have the great advantage of managing humidity in a room where moisture can be a problem. They are also adjustable so that you can set the level that is best for your home.
The other options are PIR controlled extractors. These basically sense whether there is someone in the room and switch the extractor on appropriately.
Both of these can also have timers involved so that they continue to run after the bathroom has been vacated. Also it is worth noting the wattage, volume extracted and the noise levels of your extractors.
For those who have fairly airtight homes you might be interested in investing in a Heat Exchange Extractor. These are significantly more expensive, but can be worth while thinking about if undertaking a major refurbishment project.
The other major issue with extractors is allowing them to work properly. Avoid placing the extract so that it faces the prevailing winds. A west facing louvre will be blown closed and also rattle a lot, it may also form a weak spot in the wall and allow wind driven rainwater into the wall. Ideally we would recommend venting the extract to the north and / or east and preferably through the eaves of the roof.