A recent question and answer session posed in the Daily Telegraph about the use of trickle vents has been the source of much debate on Twitter by members of the installation community.
Jeff Howell’s advice to a reader on whether he or she needed to replace windows with trickle vents with like has served to highlight the complexities facing many a homeowner and installer.
Our parent company The Glass and Glazing Federation outlines the current correct guidance on using trickle vent windows.
All buildings have to be ventilated in order to maintain the health and well being of everyone using them. There are two kinds of ventilation: background and rapid. Background ventilation can be provided by trickle ventilators. Rapid ventilation by opening the window.
The need for background ventilation depends upon the building and how it is currently being ventilated. When it comes to replacing windows an installer will need to determine if background ventilation would be required.
If a window is not well ventilated then it can lead to condensation build up which, if left, can lead to the proliferation of potentially harmful mold spores.
Current building regulations* state that it is only mandatory to install trickle ventilators within a replacement window if there was a trickle ventilator within the existing window. This is so buildings that were originally designed to have background ventilation continue to do so. Removing such vents could lead to serious problems with condensation at any point of the room where it loses heat (a thermal bridge) and not just on the windows themselves.
The above answers the reader’s question posed in the Daily Telegraph but it was not the same advice given in the article itself which referred to a period in 2010 when originally trickle ventilation was going to be installed in all replacement windows. This recommendation was changed following discussions between the fenestration industry and the Government department responsible for buildings regulations, which agreed this would not be required.
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*Source: Approved Document F Clause 7.3: Where the original windows were fitted with trickle ventilators the replacement windows should include them.