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Temperature has hit around the lowest of the year where I live. My apartment is heated, so there is a 15C difference between indoor and outdoor temperatures.

This has led to water condensation accumulating on the indoor part of the window frames, which is composed of metal and presumably much cooler than other elements (such as the glass).

Currently I am wiping all frames every 4 hours or so. How can I do better?


EDIT: Both indoor temperature and humidity is controlled. It is set to 24C~25C and 50%~60% RH. The apartment has good sound proof installation; with double glazed windows, rubber seals on the windows and foam seals on the door gaps. Air ventilation is mainly through the combined heater/cooler unit. The apartment is a new unit built just last year.

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    As far as I understand this, the fact is that warm air from your apartment is condensing on the frame so either you're doing something (like drying washing indoors perhaps) which is generating more moisture than your ventilation can remove, or they are inefficient windows that are allowing energy to transfer from your apartment to the colder zone outside. – bigbadmouse Jan 30 '18 at 11:41
  • It sounds as though your new HVAC has been installed, and put into service without being set-up properly and calibrated. Something is not right. Can the settings be changed? – Stan Feb 1 '18 at 23:44
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Many variables to consider here.

How much humidity is in the air, how good is the isolation of walls and windows? In winter modern housing is usually isolated so good that heating makes the air too dry for comfort.

We need a certain level of humidity in the air to be really comfortable. You know the temperature of the air indoors and outdoors, but not the actual temperature of the window glass or frame. A badly isolated frame or single glass pane window might be just too cool to be any good. 20°C indoors, -5°C outdoors and ~5°C on the indoor side of the glass will lead to condensation if the level of humidity is just comfortable. If the indoor glass side is around 15-20°C, then your air humidity is likely much too high.

Badly insulated windows are not that bad if humidity is high, the most water condenses at the coolest point – and you might want that to be the mostly water proof windows. If the coldest point are the walls you will end up with very unhealthy mould development.

Window frames made of metal sound like a less than ideal choice of materials. If the are old, it's likely they act as heat pipe, cooling down rapidly and showing the effects you describe. If they are newer, they should compensate for that design problem but might have broken seals or the like.

So these things have to be considered:

  1. Increase the venting. Cold outside air has less water in it, heating that air will not be such a source for condensation.

  2. If measured air humidity is very high: Is there a source like damp clothes, lots of plants etc? Reduce the source.

  3. Are only the windows really badly insulated, have leaks? Fix the windows, replace them. But keep an eye on the coolest point in the rooms to avoid moulds.

  4. Increase the temperature to e.g. 22°C. Warmer air can hold more water.

  5. Last resort before wiping regularly (not a bad option imho if to be done only once, in the morning for example): use desiccants in front of the window. These substances suck quite a bit of moisture out of the air, silently, before the water can condense on the glass or frame. These will have to be replaced or reconditioned regularly. Commercial solutions are available, dehumidifiers also.

A fan blowing onto the window is a less than ideal solution. Although that will keep the water off the window it fails to adjust the overall humidity, increasing the risk for moulds elsewhere.

Sources with more information and some pretty pictures are 17 Window Condensation Solutions and How to Avoid and Remove Window Condensation and How to Stop Condensation on Windows.


Update:

If you have perfect control over your humidifying installations: a relative humidity of between 50–60% is on the upper side of recommended. As long as those measurements are correct and the appliance in working order, the recommended zone for RH in living areas is between 40 and 60%, problems showing usually only below 30%. So, setting the humidification target zone a bit lower should help.

  • I've added some info about the installations of my apartment in the question; see if those are helpful. – kevin Jan 30 '18 at 13:40
  • @kevin I guess they are. But aside from the general info in the answer: This seems to be the first winter for this building? Sometimes there are flaws and defects that need to be rectified. Your landlord (or however this is organised) should probably be involved and perhaps pros sent in to investigate. At first I assumed this was a very old building. These conditions in such a high level flat are not right and the general idea of how this is supposed to work seems in need of adjustment. Current guess is: RH is above what you selected, sensor compromised, defect? Tried a different hygrometer? – LangLangC Jan 30 '18 at 14:38
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You could set up floor fans to blow against each of the windows. That would prevent any water from condensing by helping it to evaporate quickly. However, this would use electricity and add noise to your apartment (even though it would be white noise).

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I would try to get the humidity DOWN to 40% if you can. If you have no control over the humidity from your building system, then maybe get your own dehumidifier. As has been mentioned elsewhere, if you are adding your own moisture to the air, it's likely to be in excess of what you think.

This may be a silly question but what are you doing with the cloth when you wipe the windows? If you leave it to "dry" in the apartment then wiping the windows is achieving nothing. You need to get the water outside in some way, the easiest would be to wring the cloth as best you can into a sink or toilet.

Even better would be to use one of these window vacuums:

enter image description here

You'll pick-up more water, quicker, and with hardly any of it managing to evaporate back into the apartment.

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