Yes, the frames for UPVC windows come with trickle vents.  These vents provide ventilation and a regular flow of clean, fresh air.  All windows now come with night vents on the sashes themselves.

Trickle vents are essentially a small slot in the window frame that allows air to trickle into the room when the window or door is closed.  They allow for improved air circulation and passive ventilation without needing to open the windows.  The improved air flow will help to reduce condensation.

Trickle vents can usually be opened or closed which means that you can control the amount of air coming into and out of the room through them.  This means that you can minimise heat loss or draughts on colder days while also controlling the amount of humidity that is present in your home.  Trickle vents are particularly useful in allowing you to retain some airflow in the house while you are out.  Rather than needing to leave a window slightly open, the vents will allow air to move without compromising your home security.