Windows Question

Retro-fitting trickle vents to upvc windows

another thread, aa40 asks:
"My first floor flat is suffering from condensation on the uPVC windows and there's now damp signs appearing on the walls too. I've read that fitting trickle vents to the window frames should solve the issue. I think this is a easier solution than fitting air bricks to each room. Appreciate any feedback? Thanks"
B J D BUILDING/ROOFING correctly says
"Simple enough job to retro fit trickle vents to window heads, Window manufacturers will stock them in colour to suit. Basically drilling holes in head of frame couple of screws to fix"

however: Tim Harris MD oak leaf windows ltd, appears to have misunderstood the question, he talks about condensation INSIDE the glass unit, and recommends replacing the units with new A-rated units.
If the questioner states there is condensation on the walls, then this problem is clearly not limited to a problem with the double glazing units, and must be a general problem with condensation on cooler surfaces due to the humidity level in the room ( a very common problem in UK homes).
Therefore the only solution is to either increase the insulation on ALL the affected surfaces OR increase the amount of ventilation, either via trickle vents, night latch, core vent (which I wouldn't recommend unless required for heating/cooking appliance) or heat recovery ventilator.
Putting in new A-rated units (if existing units aren't already A-rated), may well improve insulation, save some energy and earn a bit of cash for a double glazing company, but is unlikely to solve the problem of dampness on the walls!

Regards,
Brian Goss,
Building services engineer.

2 Answers

Fitting trickle vents to the windows can offer a good solution to help air flow, but the source of moisture in the atmosphere of the flat should also be considered. Regardless of how highly specified the double glazing is, i.e. gas filled units and low-e glass, if there are excessive sources of moisture present from cooking, or drying clothes etc. double glazing can sometimes condensate on the inside, even in new build properties that adhere to all current building regulations for insulation, ventilation etc. Small amounts of condensation can appear on the glass, as it will always be one of the coldest spots in a room. A lot of new build properties have overhead vents above the frame, but in this case I would suggest that trickle vents should be fitted through the head of the opening sashes. If there is no steel reinforcing in the windows, it is an easier task. The more sashes you have, the more vents can be fitted to aid air flow. Regarding the walls having condensation - this will probably be due to a lack of cavity insulation if it's an older property. Again, trickle vents may help aid air flow and ventilation, but no guarantee if the moisture content is high.

Answered 15th Feb 2012

Altered Space Interiors

Member since 10 Feb 2012

buildings have to be ventilated in order to maintain the health and well-being. Two kinds of ventilation: Rapid and background the latter ventilation can be provided by trickle vents. Rapid ventilation open the window. The need for background ventilation depends
upon the building and how it is currently being ventilated or used. good replacement window certified fitters would advise on this requirement. If a window is not well ventilated then it can lead to condensation build up which, if left, can lead to mold spore growth. 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. (equivalent or better). it may be your window do not have sufficient insulation around them which causes cold bridging and in turn attract condensates. Check for a good seal of caulk around the new window. If there are no vents then you need to ensure air changes in the property by either rapid venting (open window) or introduce dehumidifiers / good quality vents that open when relative humidity of the property zone area is above 70 (not temperature; humidity) you can fit a passive vent system or humidistat to new or existing extractor fan vents. Passive background air bricks etc. do not cut the mustard when you dry clothes in the property or if you have lots of people living there (2 litres of water per person per night can be released in the atmosphere just from breath and sweat.. Yeuk!
Good luck
Phil

Answered 4th Feb 2016

PMV Maintenance

Member since 10 Jan 2012

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