Internally beaded windows
Window glazing is held in place against the frame with a small strip called a 'bead' which runs along all the edges of the window sash.
Early uPVC windows had the option of external beading, but this has largely been dropped due to security concerns. Window beads used to be a lot weaker and offered an easy opportunity for burglars to simply peel them away and remove the glass.
Most windows nowadays have internal glazing beads, which is the most secure option.
Multi-point locking
There are many more options regarding locks, offering varying levels of safety and security.
Technically, a window with just two locking points can be considered "multi-locking." The more points that can be locked, the more secure it is. There isn't a standard number of mechanisms, but if you can find a window that has eight or more locking points, you have yourself an incredibly secure window.
Bi-directorial locking adds a layer of complexity in the frame that prevents the intruder from being able to jemmy your window out of place.
Key lockable handles
All modern window handles are key lockable, making it difficult for potential intruders to simply wriggle your windows open. It also adds an extra safety feature for top storey rooms accessible by children and vulnerable. It is recommended that you leave your key inside the lock, however, so it is accessible in event of an emergency.
Hinge-side security brackets
Some uPVC window frames incorporate tough, interlocking brackets that secure the outside of a window sash when fully shut and locked. This means that if an intruder tries to lever the window on the hinge side, the brackets will prevent them from being able to lever the window out of place.
Egress hinges
Used for fire escapes, egress hinges allow a casement window to open fully outwards in order to provide an emergency exit.
Opening restrictors
Opening restrictors limit how much a window opens, either by connecting the sash and the frame via a cable, or by fitting key-lockable restrictors that allow windows to open no more than a couple of centimetres wide for ventilation purposes.
The Royal Society for the Prevention of Accidents reports that 4,000 children under the age of 15 are injured falling from windows every year. Something that could easily be prevented by using window restrictors.
Lockable ventilation & night vents
Windows have the option of leaving a small, one inch gap when closing known as the night vent position that many people use as a means of ventilation. However, leaving a window on the latch is far less secure than shutting a window fully, and can present an opportunity for a potential burglar to prise open the window.
New windows can be provided with 'trickle vents' instead, which provide background ventilation without compromising the security of your home.