The highest level of security fitted by the manufacturer on most aluminium windows, including coated aluminium, is a locking handle, but, whilst it would be satisfactory to most insurance standards, it is not particularly secure. This is because it is the handle which is being locked and not the window. As most handles are not of a good casting standard they have a tendency to break under pressure, or come loose from the frame.
It is possible to fit extra locks to aluminium windows, but care should be taken to ensure that there is enough metal around the window to be able to fit the lock without contacting the glass. Suitable locks designed for this purpose are available.
In the case of sliding horizontal aluminium windows, additional security can be achieved with the fitting of a key operated clamp on the bottom rail of the frame. Windows are often left open to allow the circulation of air, particularly in hot conditions. This, inevitably, reduces the level of security. By fitting a sliding window lock to the bottom rail you can restrict the slide to a few inches.
Alternatively, drilling a small hole through the bottom rail at the point at which you wish to restrict the slider and inserting an appropriate sized bolt will suffice. Additionally, to prevent the slider being lifted, fit a wooden block of a suitable depth into the track above the slider.