ᐅ Moisture in Window Frames

Hello everyone,

We have a terraced house, built at the end of 2008. The windows installed are made of uPVC.

With some of the windows, we have an issue with moisture forming in the frame. This has even started to cause some minor mold growth.

Since I don’t have much knowledge about windows, I will try to describe exactly where the moisture is appearing.

Here is a link to the installed profile:

In the first chamber (seen from the right), moisture is forming.

Droplets frequently appear, distributed unevenly within the frame.

Here is a photo showing the moisture buildup:

All the locks are adjusted to maximum pressure. Here is an example:

The counterpart looks like this:

When I clamp a sheet of paper between the frame and the sealing gasket (from the inside), I cannot pull the paper out at the bottom window edge, but it can be easily removed from the side.

Does anyone have an idea of what I can do about this?

Is this a defect?

Best regards,
Timo

Hello!

Of course, it is difficult to make a diagnosis remotely, but I will try to explain what the possible causes might be.

Here are some initial assumptions from my side, based on looking at the window frame. It appears to be a – let’s say – "budget-friendly" product:
- Relatively shallow construction depth (which explains the red-marked steel reinforcements in the frame and sash = poor for thermal insulation but necessary for stability)
- Double glazing with a relatively small gap between the panes (the gap becomes smaller the "thinner" the frame profile is): less space means less volume of argon gas inside = poor thermal insulation
- The spacer (the part with the small balls between the panes) might be made of aluminum (inexpensive but poor thermal insulation); in addition, the glass is not fully bonded around the edges (bad for insulation)

Overall, this seems to be a window that performs significantly better than a 20-year-old window in terms of insulation, but it is rather at the lower end by current standards.

Please correct me if any of my assumptions are wrong.

From your photos, I cannot see any defect in the window itself, and the seals also appear to be in good condition.

An important point would be to know how the installation was carried out.
Was it installed according to the RAL method? If yes, how exactly? If not, what method was used?
What is the wall structure? (Brick thickness, exterior insulation system, thermal plaster, etc.)
Poor installation could be a reason for the issues…

Additionally, problems with condensation often occur when the indoor humidity is too high, or if ventilation is incorrect. For example, constantly tilted windows can cool the wall reveal, causing warm, moist indoor air to condense in that area, which leads to mold growth.

Since you mentioned that the house was completed at the end of 2008:
It is quite possible that windows need adjustment about one year after installation, especially if the building has settled slightly during that time.
It might be pressing slightly on one side, and the hardware may need to be readjusted.

As I said, it is very difficult to make a remote diagnosis, but I hope I was able to help at least a bit by pointing out what might be causing the issues.

Hi,

thanks for your advice.

To be honest, I have no idea whether the products used here are good or bad. Since we bought this whole project from a property developer, they were probably more interested in maximizing their profit than ensuring real quality.

The panes themselves are indeed only placed into the frames, aligned with wedges, and then secured with the profiles (shown in the drawing above, to the right of the pane).

Is this installation method normal? Since we constantly have condensation on the windows, it seems to me that bonding the panes might help reduce this problem somewhat.

I’m not trying to bother the developer or the contractors with complaints, but rather to understand what is actually required or recommended. If bonding costs extra, I’m happy to pay for it. We don’t receive good support from the developer or the contractors on this matter due to their lack of time or experience.

Regarding ventilation, I think we are doing everything more or less properly. We air out the rooms 2-3 times a day by fully opening windows for 5-10 minutes. The windows are sometimes also in tilt position during this. However, I also always dry the inner window frames since mold started to develop inside one of the frames due to moisture.

Are there any documents or guides on how to properly adjust a window sash? Since our developer uses a very small company for windows and doors, the reality is that if we report a defect, often nothing happens for a few weeks, then someone arrives, hurriedly tries to do something, and leaves again. Very nice people, but unfortunately not very thorough.

What exactly is a RAL installation?

Best regards and thanks again for the information
Timo

Replies Between the Lines!

ostsee schrieb:
Hi,

Thanks for your advice.

Honestly, I have no idea whether the installed products here are good or bad. Since we bought this whole thing from a property developer, they were probably more interested in maximizing their profit than ensuring real quality.

I think so too.
But that doesn’t necessarily mean you have a low-quality product here. However, based on the profile drawing, it’s clear that this isn’t the most expensive PVC window.
I mean the design (glass spacing, spacer bars, no bonding, etc.)

The panes themselves are simply placed inside the frame, aligned with shims, and then fixed with the profiles (in the drawing above, to the right of the pane).

Is this installation method normal? Since we constantly have condensation on the windows, it seems to me that bonding could also help reduce this issue somewhat.

Exactly, the area between the PVC profile and the glass is the thermal weak point of every window.
For several years now, the spacer bars between the glass panes have no longer been made from aluminum or stainless steel, but from high-quality plastic. (If you’re interested, search for "warm edge" technology.)
Because the glass panes are bonded around the sash profile, it results in greater stability. Depending on the profile, you can largely do without steel reinforcements in the PVC profile, which also improves thermal insulation.

Of course, all these features are not "standard" if you go to a window company and ask for a low-cost offer… they come as optional extras.

“Retrofitting bonding” is not as simple as you might think. You definitely cannot do it yourself.
I don’t know your supplier or the manufacturer of this window, but in some cases the entire sash might have to be replaced.

Even then, from my point of view, it is not guaranteed that your problem will be solved because we are talking about an improvement of only a few percent.

Regarding ventilation, we think we are doing everything reasonably correctly: shock ventilation 2-3 times a day for 5-10 minutes. The windows are also partly opened on tilt during this time. However, I also always dry the inner frames, as condensation within one window frame has already caused mold to start growing.

In which rooms does this occur? Bathroom/living room? So the rooms that tend to have higher indoor temperatures (the warmer the air, the more moisture it can hold).

Are there any documents or instructions on how to adjust a window sash? Since our property developer uses a very small company for windows and doors, the reality when reporting defects is unfortunately that nothing happens for several weeks, then someone arrives in a relative hurry trying to fix something and then rushes off again. Very nice people, but unfortunately not very thorough.

I don’t think any professional company would be interested in offering free DIY instructions since that would hurt their own business.
Quality manufacturers often have a sort of "service pass," which offers one-time free readjustment. The word "free" means the customer has essentially already paid for this service at purchase.

There are people who are handy and can do this themselves. If you are one of them, you can give it a try; if not—contact a professional company.

In any case, this is just one suggested solution. I still suspect incorrect installation (wall connection).[ /B]

What is RAL installation?

[B]In short: In the past, window frames were just foamed onto the wall structure (or screwed in). Today, vapor and diffusion-tight tapes are used. Just google "RAL installation" and you will find plenty of info; I don’t need to explain it in detail here.

Best regards and thanks again for the info
Timo

Greetings back!
Even though I cannot solve your problem from several hundred kilometers away, all I can do is point out what might be causing it.

Hello!

I know that everything is more complicated from a distance.

The room where the issue occurs is in the attic. It is about 35sqm (375 sq ft) in size and has a ceiling height of 2.5m (8 ft) on the low side and almost 4m (13 ft) on the high side (shed roof).

The humidity levels are between 50 and 60%, which is similar in the other rooms on the first floor and ground floor. The temperature is around 21°C (70°F). I use the room as an office.

When ventilating, I noticed that the window sash is not completely flush. I’m not sure if this is intentional to allow the window to pull tight against the frame. When I hold a 1m (3 ft) level vertically against the sash, there is a gap of 2–3mm (0.08–0.12 in) at the bottom. This gap remains roughly the same when I lock the sash again.

Could the problem simply be caused by this?

One of the terrace door sashes also had to be replaced because it was too large and would rub when opening and closing. Alleged manufacturing issues were the cause...

Best regards,
Timo