Re: GBlist: condensation question

["Mike Rogers" <mprogers@together.net>]

Ah, an easy one.  There was actually a short thread on this about a year
ago.

The curtains are in effect insulation.  When they are closed what you are
doing is adding insulation between the room and the window.  Without as much
warmth from the room, the temperature of the inside of the window drops.
The curtains are not an airtight seal, so warm moist air from the room
enters the space between the curtain and the window, finds the cold window
pane, and condenses.

You have two options (or a combination of the two) to reduce this
condensation.  You can lower the RH in the room.  As it gets colder, this
will be increasingly more difficult, and eventually you would be forced to
lower the RH well into the uncomfortable zone.  The other option is to warm
the pane of the window slightly.  How?  By leaving the curtains open a bit.
In my home, on windows with blinds, lower the blinds on cold nights makes
the room much more comfortable.  I've found that leaving the blinds up off
the sill an inch or two, still provides most of the comfort, and by keeping
the windows just a bit warmer, I don't have condensation expect when the
temperature drops below -10 to -20 Farenheit (roughly -22 to -28 Celcius).

----- Original Message -----
From: KG <kgiansante@operamail.com>
To: <greenbuilding@crest.org>
Sent: Saturday, December 16, 2000 8:36 AM
Subject: GBlist: condensation question


> Greetings One and All,
>
> When my double-glazed windows are uncovered (no curtains), I see very
little
> condensation.  When the curtains are closed, however, I see more -- even
if
> the air feels dry.  I've been using the window condensation as a rough
> guide to when I should turn on the ventilation fans, but now I'm wondering
if
> that's such a good idea.  Why do I get more condensation when the curtains
> are closed?
>
> Thanks for your thoughts and for the stimulating reading!
>
> Kevin Giansante
> Veliko Turnovo, Bulgaria


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