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Access and use of this website and the material on it are subject to the Terms and Conditions set forth at Condensation on the inner pane of double windows
S e r
February,
1957
no. 30
CONDXNSATIOW
ON
THE IMITER PANE OF DOTWLE TdTNDOIt!Sc. 2
557
BLDG Many house
awners
a r epuzzled
bythe
appearance ofmolsture
film
of water or a s frost on t h e r r nlndow panes in w i n t e r , Thfsmoisture comes from t h e warm a i r
in
t h e home and is d e p o s l t e l l on t h ec o l d .window surface by
a
process c a l l e d condensationo This is the same a c t f o n t h a t c a u s e s m o i s t u r e to c o l l e c t on the surface of a g l a s sc o n t a i n i n g i c e w a t e r ,
The a i r
in
e v e r y home c o n t a i n s molature w h t c h o r i g i n a t e sf r o m
t h e d r y i n g of c l o t h e s , c o o k i n g or f r o m h m i d i f i e r s in the
furnace
Some m o i ~ t u r e i s a l s o a d d e d t o the
a i r
by e v a p o r a t i o n f r o m t h e skinand lungs of p e o p l e occupying t h e house, The a a d e r n C a n a d i a n home i s
more
t i g h t l y constructedthan
~ l d e r homes and t h i s t e n d s to s e a l in much of' t h i s r n o i ~ t u r e a n d t h u s r a i s e the r e l a t i v e hwnfdity w i t h i n t h ehome
.
When w a r m a? r
in
t h e home comesin
c o n t a c t with a cool wrndow ,s u r f a c e some of
the
moisturei n
it w i l l b e d e p o s i t e d on t h e glass s u r f a c e a 3 m a t e 7 or T r u s t5f
the temperature o f the g l a s s s u r f a c e i sa t o r below the "dew p a i n t n temperature, When the r e l a t i v e h m l d i t y
is lev, t h e "den p o l n t " t e m p e r a t u r e m i l l be low and c o n d e n s a t i o n w i l l
then o n l y occur
on
a v e r y cold a u s f a e e ; when -tiher e l a t i v e
hwnidltyis
high, the dew point temperature
i s
c l o s e toa i r
temparatureand
condensation w L l 1 occur on surfaces which are slightly
c o o l e r
t h a ntha
a i r
surroundingthem,
rdndaw s u r f a c e s a r ecool. in w f ~ t e r
simplybecause t h e m is a r e l a t i v e l y h i g h h e a t l o s s through windows, Double
window= p r o v i d e much better i n s u l a t i o n than single ones, but even a
triple-glazed wjndow p r o v i d e s l e s s i n s u l a t i o n than an uninsulated
f r a m e wall.
Condensation
on
d o u b l e windows I s to be e x p e c t e d , t h e r e f o r e ,d u r i n g c o l d weatheru The conditions under v k i c h this w i l l o ~ c u r c a n
be forecast, For example, condensa t i s n
r n ~
lll occur on a p ~ o p a r l g i n s t a l l e d d o u b l e mv5ndo:v when the i n s i d e t e m p e r a t u r e f s TO°Fm, ther e l a t t v e h a ~ i d i t y is
38%
a n d theout
s i d e temperature is-lO°F,
When condenzatllon o z c u r s on 'the i n n e r p a n eof
a d o u b l e w l ~ d o nit
is asignal t h a t the humidity should b e lowered, This can be accomplished by t u r n i n g o f f t h e h u m f d i f i e r
or
by v e n t i l a t i o n of t h e house tor e p l a c e the
m o i ~ t
a i r in the hoqe r - i t h d r y a i r from outside, Ther e l a t i v e h l s ~ f d i t y c a n be a d j u s t e d , a s
the
a v e r a g e outsf de t e m p e r a t u r a changes, t o p r o v i d e h t g h e r r e l a t f v ehumidity
d u r l n g m f l d w e a t h e r andlower h m 5 d i t y dur;ng p e r i o d s or c o l d w e a t h e r ,
.-
J *
3
39
-'y :; p:,. DIVISION OF EUELDING R E S E A R C H M A T t O N k L R E S E A R C H COUNCIL OTTAWA, CANADASo
f a r t h l s n o t e h a s o n l y considered c o n d e n s a t i o n w h f c h a p p e a r s on the Lnner pane of double w i n d o w s o The nzorecommon
l o c a t i o n far c o n d e n s a t i o n i s on the o u t e r or storm pane of
d o u b l e viindov~s. This I s c a u s e d by l e a k a g e of warm a i r
around
t h e I n n e r v,indovr l n t o t h e s p a c e between t.he t v m g l a s s
s u r r a c e s ,
Sinee the t e r t ~ p e r a t u r e of t h e o u t e r
-7ane
9 s l o r w ~ e r than t h a t oft h e F n n e ~ pane c o n d e n ~ a t i o n can occur on the o u t e r Dane a t
q u i t e lor.; r e l a t i v e hum1 d i t i e s , C o n d e n s a t i o n on o u t e r panes
is
o f t e n observed when the I n n e r v:indoa is r a i s e d for ventilation,
on
upstair w i n d o ~ ~ s of tinostore;.
h c u ~ e s snd on t h e lee1:~ard skde of houses d u r i n g cold windy weather, This p r o b l e ~ 1 s o v e r c m e5n
s e a l e d window units v~'?ieh p r e v e n t t h e e n t r y o f m o i s t u r e and d u s t
between t h e panes ,
CC=SI,G.]
Dear S i r s :
It
is the questfon of condensation on t h e i n s i d e oftheoretically 'Isealedt1 units which is the big problem today and it is on t h i s matter t h a t information is required. T h i s
condensati_on occurs not only on the more cheaply c onstxlucted
u n i t s but also on t h o s e of reputable companies. T M s conden- sation is almast impossible to remove and is a great incon- venience,
Yours truly, Donald Gash,
23 Normandie Rd.,