Comments on: Window Condensation: Top 10 Fixes http://chicagowindowexpert.com/2009/12/11/top-10-causes-of-window-condensation/ Nobody knows more about windows. Thu, 29 Jul 2010 20:19:50 -0400 http://wordpress.org/?v=2.8.6 hourly 1 By: Mark Meshulam http://chicagowindowexpert.com/2009/12/11/top-10-causes-of-window-condensation/comment-page-1/#comment-481 Mark Meshulam Sat, 17 Apr 2010 16:59:42 +0000 http://chicagowindowexpert.com/?p=1601#comment-481 Interesting question. The answer is, vent to the side where the lowest humidity is expected when temperatures are coldest. In Northern climates, this would be the exterior. In moist Southern climates, this would be the interior. Remember that the side you vent the airspace to will freely exchange humidity with the airspace, so you want to vent to the side with lowest humidity in order to keep the air in the airspace as dry as possible. The time this matters most is when the surface temperature of the glass drops below dewpoint, because then you will have condensation (not just moist air) in the airspace. That's bad because it can stain the glass and damage the finishes. Interesting question.
The answer is, vent to the side where the lowest humidity is expected when temperatures are coldest.
In Northern climates, this would be the exterior. In moist Southern climates, this would be the interior.

Remember that the side you vent the airspace to will freely exchange humidity with the airspace, so you want to vent to the side with lowest humidity in order to keep the air in the airspace as dry as possible.

The time this matters most is when the surface temperature of the glass drops below dewpoint, because then you will have condensation (not just moist air) in the airspace. That’s bad because it can stain the glass and damage the finishes.

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