In all new build houses, and also extensions, trickle vents will be specified by the architect / building inspector as an essential requirement within doors and windows. They are a passive ventilation system that enables air movement even when the doors and windows are closed. This is essential to prevent moisture build up and damp issues.

Document F of the Building Regulations details the requirements for ventilation in properties, and this must be adhered to in order to get a project passed by a Building Inspector. 

The aspect of this document which refers to the window industry is the “background ventilator”. This is a provision for ventilation that is either in the window/door or in the wall by means of an air brick. When this is fitted into a window or a door it is situated either in the head (the top) of the frame, the top of the opening part of the window (called the sash) or as an over glass vent (which are less common).

Most doors and windows are available with trickle vents as an optional extra, and the vents can be opened and closed at the homeowners’ discretion. Most types of vent are available in a choice of colours to best suit the window frame and be as unobtrusive as possible.

With replacement windows the general rule of thumb is to replace like for like. If, however, there wasn’t any previous background ventilation or the original amount is unknown the following is the guideline to what should be installed when replacing windows and doors in the home;

  • Habitable rooms  – 5000 mm² equivalent area of air space

  • Kitchen, utility room and bathroom (with or without WC) – 2500 mm² equivalent area of air space

It is interesting to note though, that if the windows and doors are replacing old frames that do not have background ventilation, the regulations only state that it “would be good practice to fit trickle ventilators” (Approved Document F, Section 7.4, p. 39). So if your windows do not have trickle vents, it is not obligatory to install them in new windows, and it is the homeowners choice. 

Many types of vent offer 2500mm² of air space each, so typically smaller windows in small rooms require 1 vent and larger windows (e.g in bedrooms, or living rooms, require 2 vents).  Despite the recommendations, it is often a good idea to fit as many vents as possible into rooms such as bathrooms and kitchens which can contain steamy air to help reduce the moisture in the room. 

To discuss any further details on ventilation, just get in touch with us and we will be happy to advise.

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