How to minimize condensation in unheated rooms


Material Information

How to minimize condensation in unheated rooms
Physical Description:
Teesdale, L. V ( Laurence Victor )
Forest Products Laboratory (U.S.)
U.S. Dept. of Agriculture, Forest Service, Forest Products Laboratory ( Madison, Wis )
Publication Date:

Record Information

Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 29300980
oclc - 61871983
System ID:

Full Text
Nevcmnbcr 1942

u. S. D FPT. OE 04 /4

m"T' 6 lJ43
No. P~1421
Madison, Wisconsin
In Cooperation with the University of Wisconsin


. V. 'ZS7ALE
Senior Engineer
Fuel shortages will cause mny home owners to close .nused rom for the
wimtsr nd p, tibly to leav bedrooms unheated even thouh they are in con-
vtat usn. Reducing the heated portion of the space within a luilin_-7 i ,
of course, an effective means of conserving fuel. Lowering the averae
temperature of the heated areas is another. Both means will be ir.cticed
in most homes in the Ncrthern States this winter.
Unfortunately, we can expect orme trouble from condensation during cold
weather in the rooms that are closed off and, unless -nrecautions are t-aken
to minimize the condensation, several tyes of damage may develoIe. nen
temperatures drop to 200 F. or more below the freezin, point, frost may
ather thickly on windows protected by storm sn,!h, and at much higher tem-
peraturen where no storm sash is used. hen the sun shines on these winds,
the frost will melt and. tae water can cause any number of difficulties.
Getting the sash repeatedly may cause paint to peel, putty to loosen, and
over, stain and decay. Water running down on the window sto1 will spoil the
finish. The water -:iy also run down the plaster wall belot 1 the wnow and
upen the floor, spoilinF the finish on both. Frequent liretting ma :amge
the plaster and cause buckling of the floor boards. during rrotr-cte4 cold
or-ells moisture may condense on the interior face of exterior wells and
Damage the plaster, stain painted or calcimined walls, an, loosen p, er on
ppered walls.
Consistently hirh humidities will also cease wood trial an! furniture to pick
uin moisture. Drawers and doors may swell, joints loosen, -r -U Oints be
adversely affected. Clothing and other hyeroscopic mpteri,2 will ecome
damr, and mold might develop during subsequent mild we-titer.
It des not follow that these difficulties ind Trobes e-ni1 arise in every
house or all of them in any one hcuse. W"ey are citi- onl, expr ls of
da.tge arld trouble that have developed in t 11e T7st in eated hous or
heatd. rooms of occuied houses. Corr(etive or nroective mensrc~ cn
be uase. to -rev-nt amge and zub eqent itenance cx:en-e.
jjeestinns forProtection
1. 30 not operate h=idifiers or witer pans in f nnaces, or use ~ny other
C ers tf inter tionPlly increas1nlr -huidity in heated portion of !auses n
which 7ome rooms are unheated. The crdinnry sources f moisture, uch as

Mince. ~50, B1421

cooking, dish washing, bathing, and laundry work, will maint, in considerable
moisture in the atmosphere. In fact, because of the reduction of heated
area and the lower average temperature maintained, the relative humidity
will probably be higher during the heating season than would occur under
normal operating conditions.
2. When frost on windows melts, wipe up the water on the sash -,ith a diry
cloth before it has a chance to soak into the sash.
3. Open windows on bright sunny da:s and ventilate closed rooms for 2 or
3 hours. Even on very cold days, ventilation will help to 64raw moisture
out of the rooms, at the expense, of course, of some loss of heat from the
house. When drying laundry in the basement, open windows to eliminate as
much of the moisture as possible by ventilation.
4. Install storm sash on all windows, including those of unheated rooms.
Such sash will materially reduce heat loss from both heated and unheated
rooms and will minimize the condensation on the inner ,-lass surfaces.
Absorbent salts are sometimes used in basements and cellars to reduce the
dampness and lower the humidity during the summer. This same method might
be used in closed, unheated rooms, particularly spaces that are not in
daily use rather than bedrooms where windows provide some ventilation.
Certain chemicals and salts have a great affinity for moisture and will
absorb it from the atmosphere. Calcium chloride is suggetd ic ti
not expensive and will take up about its own weight of moisture before it
goes completely into solution. It can then be disposed of and a fresh
supply used, or it could be dried over an open fire, preferably out of doors,
and reused. If used, it should be placed in shallow granite pans or glass
dishes, employing about 2 pounds per 100 square feet of floor sroace to be
served. The pans should be placed on the floor, or on a table near wrindowvs,
and in the coldest parts of the room. As moisture is taken lip the lunrips
gradually dissolve. The salt will function for 1 to 2 weeks before com-
pletely dissolving.
Reducing the humidity by use of chemical salts, Till not entirely eliminate
condensation on windows during severe cold wreather, but should materially
reduce it. It will not create an objectionable odor nor cause danage to3
furniture or clothing in the room. Spilling the solution, especially on
metals, should be avoided an the solution is corrosive.

Mimeo. No., R1421

3 126 089'24 5517