Bedroom condensation

December 15, 2019
Condensation diagnosis by BT
  1. If you have up to %50-%55, you should not get condensation on double pan window.

I had single pan that was every morning totally wet, I could fill a glass with the amount of condensation on that window. Replaced it with double pan and now there might only be a bit condensation on the lowest half inch of the window (lower -> colder).

Condensation happens as a factor of:

  1. Indoor air relative humidity
  2. the difference in temperature between the inside and outside air.

If you keep your house warmer, and that in turns heats the inside surface of the window, you will get less condensation. That is why people explained that if you do not cover your window with curtains you are less likely to get condensation. That is because the inner surface of the window now gets heated by the inside air. When you cover the window, you are increasing the insulation for the house (good thing) but that is because you are no longer hearting the inner window surface. So, the inner window gets colder. When it gets colder, the air in the room comes in contact with it and cools down.

When Air cools down, this is where it is important to understand relative humidly. The humidity you measure is relative. Relative to the air volume. I hope everyone remembers that the volume of the air changes as a function of its temperature. So, if you measure 60% humidity at 70 Degrees, you will see that when the air cools down to lets say 50 degrees the humidity will rise (don't know the formula, but lets say it can rise to 75%).

So why do you get condensation?

  1. because the surface of the window is cold (either draft, it being single pane or badly insulated double pane, or it is simply cold in your house)
  2. And because when the air in the room reaches that, its relative humidity approaches 100% and you get water.

Things you can do 1. lower humidity (measure it first) by ventilating the house when outside humidity is lower 2. keep humidity low by using external air fans when showering and cooking 3. improve the windows insulation (but you said it is new, so I guess you tried that. unless you bought a single pan window...) 4. Improve window insulation by using Bubble Wrap (I tried it, it works!)

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