[Greenbuilding] condensation on storms
RT
archilogic at yahoo.ca
Thu Oct 24 14:25:40 CDT 2013
on Wed, 23 Oct 2013 23:39:42 -0400, Benjamin Pratt
<benjamin.g.pratt at gmail.com> wrote:
> Although I caulk all my windows with removable caulk every Fall, the
> storms always get quite a bit of condensation on them, especially on the
> top floor in the rooms adjacent to the shower.
Ben;
My parents' century-old home used to have wooden-sash exterior storm
windows that were put up every Fall and removed every Spring.
On the bottom rail of the sash there four 1.5 - 2 inch holes arranged in a
pattern and there was a pivoting flap which could be opened as required.
As a kid I just assumed that those ventilation holes were to allow fresh
air into the house if desired. In later years it occurred to me that they
were to facilitate drying of moisture build-up between the double-hung
windows and the storms.
About 30 years later when building my own home, I installed Pella [spit!]
windows because they were considered the best ( but in reality, just the
best promo literature).
This was back in the days when they offered a removal interior pane which
clipped into the wooden sash and used compression bulb gaskets to provide
the air seal.
Unfortunately, the folly of Pella's [spit!] design became apparent the
first heating season when condensation formed against the inner surface of
the exterior pane of glass. Pella [spit!] had designed the wooden sash
with two 3/8" dia holes drilled through each of the four rails, with
plastic sleeve inserts in each of the holes which could capture a plastic
ball "plug".
Which of the holes received a plastic ball plug was determined by the
orientation of the sash. (ie Awning window sash are casements flipped 90
degrees).
Some of my windows had fogged up because paper wasps had plugged up the
ventilation holes with mud.
D'Oh!
You may be too young to remember but there was a time when sealed
insulating glass units sometimes had a small breather hole drilled through
the outer pane of glass in an upper corner to allow moisture between the
panes to cook off.
The point of all of the above ? In the past when window makers
acknowledged that they had difficulty making a perfect air seal, they
provided ventilation holes in the outer pane to exhaust any moisture that
got into the air-space. In century-old homes, where air-leaky sliding
sash and trim were common-place, the ventilation holes were huge (ie 4 x
1.5-2" dia holes) In Pella [spit!] windows in the 70's & 80's of the
previous millenium, where the window units are kinda tight, the vent holes
would be two 3/8" dia holes.
In old sealed insulating glass units, the vent hole would be one 1/8" dia
hole.
The size of the vent holes that you'd need would, I imagine, fall
somewhere between Pella's [spit!] and the
1/8" hole in the old IGUs. That would be the quick/dirty solution to your
problem.
The better solution would be those mentioned by Mike and Topher ...
interior storms with very good air seal and lowering interior humidity,
either by exhausting it at the source and/or dehumidification.
Unfortunately for me, those Pellas [spit!] that I installed in my home
have proven to be very longevous
(no edge seals to fail, aluminum cladding on frames and sash) so they're
still being used. I dealt with the lousy air seal of the removable inner
pane by making interior storms which snap into the space which the
(inteior) insect screens vacate when cold weather comes.
I went to the local H4H ReStore and got a bunch of 4 mm glass that was
used in 1950s-era sash-less sliding windows and inserted the glass into
mini-frames made out of 0.5 " x 1" pine, with Shoji/Greene & Greene-style
muntins to restrain the long flimsy perimeter pieces. The interior storm
creates a 13/16" air-space.
The interior storm sash is made smaller than the actual opening to allow
for a screen spline "gasket" to be compressed into the gap to provide the
air seal. The screen spline is reusable year after year but you could use
your peelable caulk if you can't be bothered futzing with the screen
spline.
As a belt & suspenders strategy, I also insert a piece of silica
gel-filled spacer bar (salvaged from dismantling patio door IGU) at the
bottom of the air-space and include a brake-formed sheet metal
condensation gutter (to match the profile of the bottom sash rail (set in
place before the storm is put in).
--
=== * ===
Rob Tom AOD257
Kanata, Ontario, Canada
< A r c h i L o g i c at Y a h o o dot c a >
(manually winnow the chaff from my edress if you hit "reply")
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