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information
copied verbatim from original model 25 Spartan Manor owners manual
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The
problem of condensation in houses, stores, shops and other buildings always
exists during cold winter weather. This problem is not uncommon to trailers.
No houses or house trailers can be said to be immune to condensation under
certain conditions of weather and use. This bulletin, for lack of space,
will not attempt to discuss more than a few fundamentals of the subject,
and that very briefly
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| We quote from an article in Consumers Research of March, 1943, entitled "Winter Humidity in Houses and the Problem of Condensation on Windows and Walls" |
| "The maximum amount of water vapor which can be present in air without condensing decreases with lowered temperature; relative humidity is the proportion which the actual amount of vapor present bears to the amount which represents saturation. In cold weather, even at 100% humidity, the actual moisture content of outdoor air is low in comparison with the moisture content of the room air. When this inside air comes into contact with a surface which is much colder, such as the glass of a window, a portion of the moisture condenses on the colder surface. Moisture of condensation of a window causes annoyance and possibly damage to paint, wallpaper, and plaster, if not wiped off the wood of the window and sill. Since the warm air of the room has a higher vapor pressure than the colder outside air with its lower moisture content, vapor tends to pass through walls of the room to the outdoors. When this vapor in its travel form the interior to the exterior meets a surface which is sufficiently cold, it condenses there just as it does on windowglass on a very cold day. Thus condensation may occur inside the exterior walls of a house, with the resultant eventual rotting of wood and insulating materials. It can even cause serious damage houses of brick or stone. Condensation in attics is perhaps more often noticed by the house holder than is condensation in outside walls, since in the attic the presence of condensed moisture often makes itself known. Often, in a house with tightly constructed roof with no open windows or louvres in the attic to permit air circulation from outside, water dripping to the attic floor may leak through and stain the ceiling. |
| For these reasons, unless effective "vapor barriers" are used to bar the passage of vapor through the walls, it is important to keep humidity at reasonably low levels, especially in well-insulated houses. Since the vapor pressure is dependent upon the difference between inside and outside temperatures, the colder the weather the lower should the relative humidity be kept. The U.S. Department of Agriculture Forest Products Laboratory recommends that in order to prevent damage to wood walls, and framing of the house the relative humidity inside of house be not permitted to exceed about 20% in sub-zero weather, and about 30% at temperatures below 15 degrees F." |
| ".....Natural sources of moisture in the household often produce more humidity than is desirable and more than would be evaporated by common types of humidifiers; such sources are respiration of occupants and of potted plants, laundering, cooking, bathing, gas and kerosene heaters not connected to a flue." |