What are Trickle Vents & Do I Need Them?
Trickle vents are set into the frame at the top of the bifold door panels, and allow air to flow through. They can be opened and closed, as required.
The law now requires all new windows and doors to have them. The only exception is if you are replacing existing doors that do not have trickle vents. One trickle vent per door set is usually enough. Your architect will be able to clarify this for you.