From: Eunoia Eigensinn 
Newsgroups: alt.home.repair  misc.consumers.house  alt.building.construction
Subject: Re: Bow windows and condensation
Date: Tue, 17 Feb 2004 20:54:04 GMT

Eric;

If your comments about "seal contact" are intended to suggest that cold air 
leaking in around the window sash are a cause of the condensation on the glass, 
I'd have to disagree and say that the opposite is often the case.

On a window which is fogged up due to condensation, if there are small air leaks 
present around the sash, one will usually see clear areas on the glass 
immediately adjacent to the point(s) of leakage, but there will also likely be 
puddles of water (or ice) below that area too, on the sill.

Even cooler air which is moving fast enough past the glass so as to not linger 
long enough to reach the dew point, will not result in condensation.


If re-routing the warm air supply vent to immediately beneath the window as Rob 
Tom suggests is not an option, a reactive solution would be to make shallow 
sheet metal pans or troughs to collect condensate so that it can't wet moisture-
susceptible materials; the same principle as that of placing condensation 
gutters beneath the edges of skylights. 
If the condensate isn't too plentiful or there is someone around to empty the 
accumluations regularly, then drywall J-trim (or similar) may suffice for the 
gutters.
  

On Tue, 17 Feb 2004 12:09:17 -0500, "Eric Ryder"  
wrote:
> 
> "LD"  wrote in message
> news:ed86be0a.0402170433.45a09239@posting.google.com...
> > Greetings all;
> >
> > We have massive condenstion on both our bow windows.
> > Not in any of the bathrooms, not in the kitchen, not on any of the
> > original awning windows (dating back to the 60's).  The living room
> > has two windows:  one awning, one bow window.  Condensation affects
> > ONLY the bow window.
> >
> > I'm beginning to think that the problem could be due to a defective
> > installation - or to a poor-quality product.  (We don't know who
> > installed them, or when.  They were there when we bought the house.)
> >
> > We have to replace them (the gyproc underneath is beginning to rot).
> > Can we have new bow windows put in, or would it be safer to go with
> > something that does not project out too much from the wall of the
> > house?
> >
> > TIA
> >
> > LD
> > Ottawa, Canada
> 
> The previous post re: heated airflow is one part of the problem.  Large
> windows dump heat.
> 
> Bow windows are typically casements, which should seal as well as the
> awnings from the same window order.  Exceptions would be 1)large sash with
> insufficient draw locks (ie 6' sash with a single locking point) and 2)
> Inadequately supported bow and bay combos often sag from the unit weight and
> roof construction.  This would affect the seal contact.  To determine if
> this is contributing, examine the side (flanking) sash for an out-of-square
> condition relative to their frames.  A 45 degree projection bay with large
> flankers would be the most likely to exhibit this, a three unit bow with
> small flankers the least likely.
> 
> Also, the head and seatboards of projecting windows should be insulated in
> heating climates.  Sounds obvious, but I've seen it omitted often.  This
> would create a zone of cooler air on the inside of the windows, contributing
> to condensdate.
> 
>