Now that the temperature outside has dropped, the windows start to accumulate water vapor. I am assuming that it might also lead to that black stuff forming. Is there a more efficient way of dealing with the condensate than wiping it dry every day?

  • waka@feddit.de
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    11 months ago

    Couldn’t solve this as well so far. Looking at it with a thermal camera in cold weather revealed insufficiently insulated windows as the root cause. Basically the frame holding the glass sandwich itself is thermally too conductive at the seam, which tends to be a lot colder than the rest. If the difference is too low, condensations forms depending on the current dew point in your room. As a rule of thumb, if you have 22°C inside and 59% relative humidity, you have a dew point of around 14°C. If your insulation on the windows gets below that, humidity condensates there first. Airing out the room can help lower the dew point, but usually that’s barely enough.

    The only fixes to lower the dew point are reducing relative humidity to inhumane levels (below 30% relative) or increasing the room temperature by alot (more than 25°C), all combined with several airing out of the room for 5 minutes 3x daily all winter.

    Other things to do are identifying and monitoring high-humidity rooms nearby. Most likely your bath with a shower inside. If you have a “dark bathroom”, meaning now windows and just a vent, switch the vent for a humidity-controlled version and dial it in on around 63% humidity. Install a vent in the door near the bottom as well if not existent already, since a closed door chokes the vent. Once the door opens, water vapor enters the flat/house and raises the humidity quickly.

    The only ultimate solution to this is replacing the entire windows with three-panel versions in properly insulated frames, reducing constant water vapor sources like in baths and kitchens using whatever venting methods work best there and lastly (most likely impossible due to cost if you are not considering building a new house) switch from traditional radiation heaters to an air conditioning heating/cooling solution which levels out most of the humidity issues electrically.

    • GewoehnlicherHamster@feddit.de
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      11 months ago

      This is a detailed answer with which I largely agree, I just want to point out that the installation of better insulated windows shifts the problem in insufficiently insulated buildings to other areas, often the moisture then settles in corners and leads to mould there - in the past it was said that the window should always be the coldest surface in the room, today there are Ventilation, insulation,… but i think this is still a good rule

    • the_third@feddit.de
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      11 months ago

      Basically the frame holding the glass sandwich itself is thermally too conductive at the seam

      Could it be, that the seals have aged and don’t seal as well anymore? A constant draft through there would probably lead to a cold frame as well.

      • waka@feddit.de
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        11 months ago

        Interesting idea. The thermo cam shows a consistent stripe of cool area where the seal sits all around the window. Not sure…

        • the_third@feddit.de
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          11 months ago

          Easiest way to find out: Get some TesaMoll in the right size and try it out on one window.

          • waka@feddit.de
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            11 months ago

            Ah, my bad. I meant the silicone sealant of the glass pane where it meets the frame. The regular seal - while originally bad - has been fixed already. So it’s really the seal where the glass pane meets the movable window frame, not where the movable frame meets the frame fixed to the walls, if that makes sense.

            • the_third@feddit.de
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              11 months ago

              Yeah, makes sense. That would be unusual. Only thing I could imagine is water entry into the frame, if the outside seal on the glass was bad. The part we can see in the picture looks alright though.

              Usually, it’s one of those two white seals that lose proper contact with their counterpart surfaces, either because the wood deforms irregularily (and thus gets bend) or because the whole moving frame needs to be readjusted to close tighter. Bit weird in your case, as you say they are fine. How is the temperature in the middle of the pane?

              • waka@feddit.de
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                11 months ago

                A picture should explain this better. Middle of the pane is difficult to measure in Infrared, but a regular probe taped to it shows about 18°C right now, so just a bit below room temperature. I assumed this behaviour is normal, since all windows in my rental are like this. Note that this windows specifically has not been resealed at the movable part of the frame yet. However, as you can see, it’s not the coldest point of the entire window either. Outside temperature was -3°C when the photo was taken.

                • the_third@feddit.de
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                  11 months ago

                  It doesn’t seem, that the movable part of the frame is even that cold. From the scale I’d estimate it at 17°C or so? It really seems that the contact between the frame and the pane is the weak point.

                  For comparison, I’ve just gone and measured my relatively new windows, about 3 years old, plastic frame. Its -3°C outside as well.

                  I’ve measured my pane temps by sticking a bit of matte tape to it:

                  The pane is about 3°C colder than the ceiling and the floor:

                  In my case, the coldest part is the fixed part of the frame:

                  The contact area between the pane and the frame doesn’t cool off nearly as much as it does in your case. I guess, that’s your answer regarding the condensation. Not much you can do about that, it seems :/

                  EDIT: Yeah, I think that is it. Just had a look at how the panes are fitted into my windows: The plastic frame overlaps them AND the pane edges aren’t metal or at least the metal is covered. In your case, the metal frame is isolated from the inside and the outside basically just by a bit of silicone. That’s probably what makes this heat bridge a lot less critical in my case.

                  • waka@feddit.de
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                    11 months ago

                    Thanks for the feedback! So, bad windows in my case. Either way, badly insulated windows just tend to form condensation it seems.

                    I guess in the end it’s the usual: Regular short cross-venting and wiping off moisture - or go on an insane money spending spree on insulation and air conditioning.