Hello everyone,
I have a problem that is somewhat bothering us...
We recently moved into a rental apartment. Great location, great landlord, everything really excellent.
The bathroom was renovated 5 years ago, including a new window.
Now we noticed the following:
- There is always moisture on the silicone sealant on the bathroom window sill. Even if we wipe it away, it reappears a few hours later, although we always ventilate after showering or bathing.
- As a result, some black mold has developed there, which we cannot remove.
- Right in front of the window/window sill is the bathtub… when sitting in it, you can feel a “draft” at the back of the neck.
- Using Tesamoll to fix it didn’t help; the sealing lips are now tight, but the draft remains. Taping over the small openings also didn’t help.
According to the outdoor sensor of the weather station, the window sill is below 17°C (63°F) and the humidity is above 70% with the window closed and nobody having showered or bathed recently.
If the sensor is placed in the middle of the room, the temperature rises and the humidity drops. Don’t worry, I was just curious how far the sensor reaches 😉
The landlord wants to address the problem, which I feel uncomfortable about because it means the entire beautiful tile work might have to be removed if the insulation foam around the window frame isn’t sealed properly. I find the landlords (a couple) very likable and understanding, and he also feels awkward and quite frustrated about it :-/
Most importantly: what about warranty after 5 years? The seal seems tight, and the window as well… so is this just poor original workmanship that only becomes obvious now?
So... we need help to maybe check where the fault lies beforehand :-/
What should we do? What else I noticed: the bathroom (3 x 4 meters (10 x 13 feet)) is unusually cold in the morning (facing the weather side). There are no blinds or shutters to close… :-/
I would appreciate any tips.
Thank you in advance,
Regards,
Daenni
I have a problem that is somewhat bothering us...
We recently moved into a rental apartment. Great location, great landlord, everything really excellent.
The bathroom was renovated 5 years ago, including a new window.
Now we noticed the following:
- There is always moisture on the silicone sealant on the bathroom window sill. Even if we wipe it away, it reappears a few hours later, although we always ventilate after showering or bathing.
- As a result, some black mold has developed there, which we cannot remove.
- Right in front of the window/window sill is the bathtub… when sitting in it, you can feel a “draft” at the back of the neck.
- Using Tesamoll to fix it didn’t help; the sealing lips are now tight, but the draft remains. Taping over the small openings also didn’t help.
According to the outdoor sensor of the weather station, the window sill is below 17°C (63°F) and the humidity is above 70% with the window closed and nobody having showered or bathed recently.
If the sensor is placed in the middle of the room, the temperature rises and the humidity drops. Don’t worry, I was just curious how far the sensor reaches 😉
The landlord wants to address the problem, which I feel uncomfortable about because it means the entire beautiful tile work might have to be removed if the insulation foam around the window frame isn’t sealed properly. I find the landlords (a couple) very likable and understanding, and he also feels awkward and quite frustrated about it :-/
Most importantly: what about warranty after 5 years? The seal seems tight, and the window as well… so is this just poor original workmanship that only becomes obvious now?
So... we need help to maybe check where the fault lies beforehand :-/
What should we do? What else I noticed: the bathroom (3 x 4 meters (10 x 13 feet)) is unusually cold in the morning (facing the weather side). There are no blinds or shutters to close… :-/
I would appreciate any tips.
Thank you in advance,
Regards,
Daenni
Hello again... although I’m surprised that apparently no one knows about this problem...? Or is this the wrong forum? Hm...
Yesterday, I tested with the laser thermometer...
The lower edge/silicone seal of the bathroom window (still on the windowsill) showed a solid 8.5°C (47°F). Other rooms (including the kitchen) measured about 14°C (57°F) in the same spot.
So there must be some kind of leak at the bottom, right?
Best regards and thanks
Daenni
Yesterday, I tested with the laser thermometer...
The lower edge/silicone seal of the bathroom window (still on the windowsill) showed a solid 8.5°C (47°F). Other rooms (including the kitchen) measured about 14°C (57°F) in the same spot.
So there must be some kind of leak at the bottom, right?
Best regards and thanks
Daenni
A
Andreas Euler2 Feb 2010 17:26Hello Daenni,
It is clear that the lower sealing was not installed during the window installation. This sealing was already part of the generally accepted technical standards five years ago and must be included. Whether this constitutes a hidden defect is something a lawyer should advise you on, as I am not authorized to give legal opinions.
To ensure the window is permanently sealed, an outer vapor-permeable layer and an inner vapor-retardant installation must be applied. This is usually done by integrating the window into the airtight layer of the masonry.
To properly fix this now, the window would ideally need to be removed and reinstalled correctly. However, this will likely damage any tiles if they are still in place. If tiles are present, I would recommend proceeding with this method. If not, there is an alternative: so-called cover strips that can be installed both inside and outside.
Your description raises some concerns because the temperatures seem unusual. There might be a thermal bridge present, which should be investigated—ideally using a thermal imaging camera.
The temperature should never fall below 12.6°C (55°F), as mold growth becomes almost unavoidable below this level. If mold is already present, the sealing should be completely removed, treated with a mold-killing agent (such as isopropanol or hydrogen peroxide), and then replaced with new sealing.
I hope this helps you.
It is clear that the lower sealing was not installed during the window installation. This sealing was already part of the generally accepted technical standards five years ago and must be included. Whether this constitutes a hidden defect is something a lawyer should advise you on, as I am not authorized to give legal opinions.
To ensure the window is permanently sealed, an outer vapor-permeable layer and an inner vapor-retardant installation must be applied. This is usually done by integrating the window into the airtight layer of the masonry.
To properly fix this now, the window would ideally need to be removed and reinstalled correctly. However, this will likely damage any tiles if they are still in place. If tiles are present, I would recommend proceeding with this method. If not, there is an alternative: so-called cover strips that can be installed both inside and outside.
Your description raises some concerns because the temperatures seem unusual. There might be a thermal bridge present, which should be investigated—ideally using a thermal imaging camera.
The temperature should never fall below 12.6°C (55°F), as mold growth becomes almost unavoidable below this level. If mold is already present, the sealing should be completely removed, treated with a mold-killing agent (such as isopropanol or hydrogen peroxide), and then replaced with new sealing.
I hope this helps you.
Hello Andreas,
Thank you very much for your response.
Well, the landlord apparently spoke with a building biologist who was involved in the planning back then.
Her statement: Mold exists everywhere and always (apparently more where there are window sills, which still seems logical to me).
Also, that this silicone sealant mold is nothing new and “not a concern”… well.
She also said that the temperature difference is normal because it’s a stoneware window sill, which naturally insulates less.
Options: remove the window sill and replace it with a plastic one.
That all our window sills are made of stone shouldn’t really be a big factor here 🙄
So, in my opinion, this explanation is nonsense.
As I mentioned above, I already measured the temperature, and it seemed very strange to me that with the same window dimensions and the same window sills, there is a 6-7 degree difference behind it. Even if it’s the windy side... the room is 3 x 4 meters (10 x 13 feet) in size, has a radiator that can be set to level 5 of 5, and it’s still cold… so, we’ll wait and see.
What is positive, however:
the landlord didn’t really rely on her statement (he was already here today, although he was only allowed to inspect on Sunday) because there really is a draft. Also, in the apartment below (where his son lives), there is no draft and no dampness.
His plan: remove the tiles, then assess and possibly redo.
I would call this a defect. Not toward the landlord (he is genuinely trying), but regarding the building biologist (who says from a distance that the mold is not harmful) and the window manufacturer who apparently forgot something.
By the way, the facade was completely insulated back then, so it should provide good insulation.
Let’s see how this develops.
Thanks again to you!
Best regards,
Daenni
Thank you very much for your response.
Well, the landlord apparently spoke with a building biologist who was involved in the planning back then.
Her statement: Mold exists everywhere and always (apparently more where there are window sills, which still seems logical to me).
Also, that this silicone sealant mold is nothing new and “not a concern”… well.
She also said that the temperature difference is normal because it’s a stoneware window sill, which naturally insulates less.
Options: remove the window sill and replace it with a plastic one.
That all our window sills are made of stone shouldn’t really be a big factor here 🙄
So, in my opinion, this explanation is nonsense.
As I mentioned above, I already measured the temperature, and it seemed very strange to me that with the same window dimensions and the same window sills, there is a 6-7 degree difference behind it. Even if it’s the windy side... the room is 3 x 4 meters (10 x 13 feet) in size, has a radiator that can be set to level 5 of 5, and it’s still cold… so, we’ll wait and see.
What is positive, however:
the landlord didn’t really rely on her statement (he was already here today, although he was only allowed to inspect on Sunday) because there really is a draft. Also, in the apartment below (where his son lives), there is no draft and no dampness.
His plan: remove the tiles, then assess and possibly redo.
I would call this a defect. Not toward the landlord (he is genuinely trying), but regarding the building biologist (who says from a distance that the mold is not harmful) and the window manufacturer who apparently forgot something.
By the way, the facade was completely insulated back then, so it should provide good insulation.
Let’s see how this develops.
Thanks again to you!
Best regards,
Daenni
A
Andreas Euler3 Feb 2010 08:13Hello,
you are absolutely right, what the lady is saying is nonsense.
Mold can only develop where humidity exceeds 70% and that happens where the temperature drops below 12.6°C (54.7°F), because that is where the usual indoor climate begins to condense.
you are absolutely right, what the lady is saying is nonsense.
Mold can only develop where humidity exceeds 70% and that happens where the temperature drops below 12.6°C (54.7°F), because that is where the usual indoor climate begins to condense.
Hello Andreas,
just to keep you updated... in case you’re interested 😉
Tomorrow the window installation team is coming.
Throughout the winter, we were able to wipe this lower silicone joint dry about 4-5 times a day, as condensation kept forming there.
Let’s see what the team says tomorrow.
It’s very unfortunate because it’s above freezing again, and the temperature of the windowsill has already risen above 10°C (50°F), instead of staying around 8°C (46°F).
The windowsill is now only “damp” but no longer wet.
We’ll see how things develop tomorrow... I’m curious.
Best regards and many thanks to you.
Daniel
just to keep you updated... in case you’re interested 😉
Tomorrow the window installation team is coming.
Throughout the winter, we were able to wipe this lower silicone joint dry about 4-5 times a day, as condensation kept forming there.
Let’s see what the team says tomorrow.
It’s very unfortunate because it’s above freezing again, and the temperature of the windowsill has already risen above 10°C (50°F), instead of staying around 8°C (46°F).
The windowsill is now only “damp” but no longer wet.
We’ll see how things develop tomorrow... I’m curious.
Best regards and many thanks to you.
Daniel
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