What is a window trickle vent and how does it work?

A window trickle vent, also called an air inlet, is an additional element of a window’s ventilation system. It takes the form of a small opening protected by a special cover. Some window models are fitted with vents during production, while for windows that do not have them they can be bought separately and fitted in the frame. Trickle vents are suitable for windows made of various materials, including timber, PVC and aluminium.

What are air inlets for?

A feature of modern windows is their high airtightness. Although this parameter is particularly desirable because of lower heat losses and better acoustic insulation of a building, sometimes a greater flow of air into a room is needed, e.g. in tenement houses. In this case the best solution is fitting trickle vents. They are not used, however, in buildings equipped with mechanical ventilation (heat recovery).

Types of trickle vent

Timber windows can be fitted with humidity-controlled inlets, which open or close automatically in response to a rise or fall in the humidity in a room. Their name comes from the hygrometer, that is the device that determines the level of humidity.

The second type is pressure-controlled inlets. They work automatically, and the amount of air they bring in depends on the difference in pressure outside and inside the room. The shutter closes partly when the maximum difference in pressure is exceeded, e.g. in windy weather. The user can also influence the reduction of the flow of air through the vent, but closing the damper completely is not possible.