[Greenbuilding] Humidity between multiple windows

David M Delaney ddelaney at sympatico.ca
Mon May 9 21:58:11 PDT 2011

On 5/9/2011 6:09 PM, nick pine wrote:
> Bob Klahn <Home-NRG at dnaco.net> wrote:
>> The old rule of thumb for minimizing / avoiding condensation between 
>> windows (e.g. between prime and storm windows) has been to be sure that
> the innermost window was five times tighter than the outer.
> How would you measure that?
> I might be sure the inner window is as airtight as possible and drill 
> one 1/8" weephole in the bottom of the storm window frame, and drill 
> another if there's any condensation during the first winter, and so on.

I have a childhood memory about ventilation holes in storm windows.  My 
parents  lived in Winnipeg in three houses with storm windows from 1942 
to 1975. At that time you could count on at least two winter months in 
Winnipeg  during which the average daily temperature was well below 0 
F.  I remember that the storm windows had three ventilation holes in the 
bottom of the frame of each storm window. They were about an inch in 
diameter, and were positioned on approximately 4 inch centers in the 
bottom center of the frame.  A narrow wooden flap fastened on the 
interior side of the storm window frame by a single screw in one end was 
positioned so that it could be adjusted to cover any fraction of the 
total area of the three holes.

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