Window Condensation

Hi All,

Recently finished renovating an old 1950s house, one of the upgrades to the house was new Double Glazed windows. We’re currently experiencing a real problem with condensation on the main bedroom window. Initially we had problems with all of the windows but I think that was due to dampness in the house; the house hadn’t been lived in for over a year and never had any central heating, so I put it down to the heat extracting 50 years of dampness out of the walls.

A few weeks later all the windows are fine bar our bedroom window, which on a cold morning like this morning, we can have floods of water pouring from the window. I’ve read in previous posts; to ensure that there is enough ventilation in the room and I feel there is: a small 6* 3 vent in the old fireplace and the smaller window is left slightly ajar every night.

We’ve just recently got new blinds installed and I’m worried they will go mouldy from all the water, not to mention the stains on the window board and the wet carpet….

Anyone got any suggestions, is it time to go back to the window shop and complain??


Thanks in advance

If all the other windows in the house are OK then it looks as if you have a local problem in that bedroom which seems to be extra dampness. There might have been a fault like a damaged gutter outside. I think you need to have an expert look for the problem. A dehumidifier would also work to extract the dampness if there is no continuing problem - no leaky pipes, radiator, en-suite?

No Ensuite, no leaky pipes etc..

The walls don't feel particularly damp were as in the first few weeks you could feel it in the walls. I've already asked the architect about it, he just said there's a real problem with condensation at the moment... real insightful, but I'm not best pleased with him but that's another thread..

What was the entent of the refusbishment? If the main bedroom was re-plastered, there may be still excess moisture in the walls / ceilings. As joanmul suggested, a de-humidifier may help draw out any moisture. These can be hired from HSS / Sam Hire, plug it in over a weekend and see what it draws out (remember to empty the tray regularly, you'd be suprised what these things gather!).

Check that there's not water coming from above - guttering, an overflow from the cold water storage tank in the attic or a leaky roof (was this trated as opart of the refurbishment?)

It may be that you have a 'cold bridge' - this would occur where there is no insulation between the window lintol / reveal and the outside wall. It is difficult to see without removing the window. Does the condensation mainly occur on particularly cold nights / days?

Adequate ventilation - check out your vent. It may be worth putting a new vent through the bedroom wall to the exterior. The vent size sounds small - generally it is 1/20th the room size (standard sizes can be purchased at a builders providers), 200 - 300mm (8" - 12") square should ventilate an average bedroom (say 3 or 4 m square).

The only other items I can think of that you could check out with the window installer:

Retro fit 'trickle vents' on your windows. These are small slots that provide ventilation above the window leaf, they can be open and closed as required. These would however more than likely involve additional cost, as the window leaf would have to be swapped out. You might be lucky - speak to the window installer, they might be able to swap this, these window leafs are all on standard module sizes interchangeable, so he may be able to use it some where and you pay the excess on the higher spec'd leaf.

All double glazed windows are thermally broken, and have seals around the panes to ensure air is trapped between the glass - this is how they work, any break in this seal would render the sdouble glasing near useless. Check out that the seals in the windows are not broken - this would allow condensation to develop internnally. If you can see condensation in the air gap between the two leafs, you have a a broken seal. This sould then easily be repalced.

I find we have the same problem i think it has alot to do with two people sharing a bedroom and the breathing done throughout the night, especially with fellas who seem to sleep with their mouths open alot (my boyfriend does) and he sleeps on the side of the bed nearest to the window.

The main bedroom didn't need to be plastered as the walls were in good shape. and unfortunately this particular window was not part of the overall build job, no leaks from above,

I appreciate the vent isn't very large for the size of the bedroom but the fact we sleep with the window open should alleviate the need for a larger vent in the room.

The problem is rife on a cold night. On warm nights very little condensation appears. We were going to get the gable wall pumped with insulation perhaps we should consider the front wall also..

The double glazing appears to be working as nothing appears in between the panes.

Liverlips, I do sleep by the window, but what do suggest I do, not breath

"is it time to go back to the window shop and complain??"

Not sure if I'm getting the full picture here. If you have had double glazed windows installed in the house and this job included this window you have every right to get the company back and get them to check out the problem. Did the architect not recommend this already?

No my architect did not recommend anything, as I said he's another post on to himself..


I wanted to get a full insight into the problem, I didn't want the Window company coming out and blaming everything else but the window. So I wanted to get some advice on the matter.

"So I wanted to get some advice on the matter"

Yeah, might be a good idea. Have your facts ready before they start defending themselves.

Leaving the window open over night cools down all the place around it. The frame, the pane, the wall. And cold surfaces are the point where condensation appears first. A simple physical reaction.
Have you tried "rapid ventilation" ? You should open all the windows fully to exchange the entire air content of the room. Several times a day, depending on the usage, for a few minutes. Not a quarter of an hour, that would be to long, the room surfaces would cool down to much. And the rest of the day/night you keep the windows closed and the room warm. The fire place should be closed, either with the damper or for good if you have central heating.

will try that approach and see how it goes. Will have to change the wifes habit of a lifetime though.

Surely that would mean you'd be sleeping in a room with no ventilation at all then?

To annR : If the room had been designed to the minimum building regulations or at least to good practice the volume of fresh air/oxigen should be sufficient to sleep there. If not than it's an unhabitable room, so you would need extra ventilation. Which could be provided for example by leaving the door to the hall open or by a heatrecovering ventilation unit.

we still have the vent in the fireplace, the window is only open because the wife has always selpt with the window open.

oh forgot to mention that we slept with the window closed and voila no condensation on the window but saying that, wasn't a very cold morning so I'll revert later in the week with more details