A couple of months ago we moved into a new house. We have new windows but are already getting condensation on some of them. Our windows are triple glazed, and we also have a mechanical ventilation heat recovery (MVHR) system. Between the triple glazing and the ventilation system, we thought we definitely wouldn’t get condensation. However, we regularly get condensation across the bottom windowpane. Is there anything we should do to try to fix this? Would it be a problem with the windows or do we need to improve how the MVHR is working?
This is an interesting question, and not an issue that I have been asked about or seen before, but I will give you a steer as best I can and try to resolve the matter based on the information provided.
Firstly, I note the high spec of the house, with the MVHR system and triple glazing. Both are top-quality modern installations in new dwellings in Ireland, and I agree, you should not be getting condensation on the internal face of your windows. I built my own house a number of years ago and installed both of these features also. I tend to get condensation on the external windowpane on a cold morning so I would expect that should be the case with your new build house also.
I don’t believe your issue lies with the complementing performance of the products, but may be due to a fault with one of them. I would start by checking there.
Why are we getting condensation on our new triple-glazed windows?
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It should be fairly easy to identify whether the MVHR is operating correctly, and you should check that there is power to the system and that it’s operating normally. Check the control panel and, if in any doubt, contact your ventilation contractor to check the system for you.
I suspect the issue most likely lies with the window glazing. You should check that the rubber seals are intact around the windowpane. Check also that there are no draughts that could emanate from around the glazing, which might cause condensation from cold air flows or draughts, which the MVHR might create through negative pressure.
From what you describe, the problem seems fairly localised. Modern triple-glazed windows tend to have an insulating gas in their cavities such as krypton or argon. They also tend to have specialised coatings to assist with insulating the glazing. Perhaps, through some issue in the manufacturing process, this has not happened, and these sections of the windows are performing less effectively than the other glass panes.
[ We haven’t bought a house in 35 years. How should we go about downsizing?Opens in new window ]
Moisture will typically seek out the coldest surface in a room to condense and it sounds as though the glazing panes are the weak link. It might be worthwhile contacting the supplier of the window frames and glazing so they can check them. On top of that, a simple check using an infrared camera should confirm if the panes of glass are performing differently to others in the house. If that can be established, then it is likely a simple fix in replacing those panels. Given that this is a new house, one would expect that this repair would be treated as a snagging exercise.
Aidan McDonald is a chartered building surveyor and a member of the Society of Chartered Surveyors Ireland
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