We have a large bathroom with a huge window. It looks very good for most of the year, then condensation takes hold and the paint cracks, peels and looks grim. I really don't mind how much I spend on this but I would like it sorted out once and for all. What would you do? What extractor fan (we have an outside wall) would be the best? I've no idea where to start and am suspicious of random builders who might shift whatever they've got left over rather than find an ideal solution.
The root of your problem, as you have identified, is a lack of ventilation within your bathroom, allowing cold and water-laden air to meet. Condensation then forms on your window, resulting in paint cracks and peeling. It is now a requirement under building regulations to install a bathroom extractor fan (with isolator switch) to all new build and refurbished bathrooms.
The most common type of fan is linked to your bathroom light switch. When turned on, the extractor fan runs and you can set it to continue to extract air for a few minutes after the light is turned off.
If noise is a concern to you, you will find multiple suppliers of fans that are referred to as "extra quiet" or "quiet air" - look for a fan that is within the 30-40 decibel range when on.
In order to ensure that you buy the right-sized fan, measure the bathroom and speak to the manufacturer of the fan range that you have chosen and they will propose the correct size. This will also determine the size of hole that needs to be drilled through the external wall, be it 100mm or 125mm.
For the fitting of the fan, you must use a qualified electrician (not a standard builder). Bathrooms are zoned for electrical purposes and the electrician will work out how close the fan is to a water source and whether or not it needs to be a low-voltage model.
Once the fan has been fitted, check that it is connected to ducting through the wall and then correctly attached to an air louvre vent externally. This is vital to prevent water ingress through your brick work and draughts blowing back into the bathroom.