Moisture Problems in the Home By Greg Tuttle, graduate leakage. This publication as student, Department of discusses these problems and a liquid on the nearest surface that Agricultural Engineering, and points out means to help you is Susan Mireley, associate identify whether the problems exist in cooler than the air. Three professor and Extension your home, determine their cause(s) conditions housing specialist, Department and implement effective solutions as in the home increase the chances of Human Environment and quickly as possible. that condensation will occur. The Design, first Michigan State University. CONDENSATION of these is a relatively recent phenomenon, a side effect of the efforts many homeowners have In recent years, Michigan Condensation can be a problem in taken to increase the energy Cooperative Extension Service both winter and summer. In winter, it efficiency of their homes. Many staff members have reported an often appears on windows first in the have added insulation to cut heat increase in the number of form of fog or ice on window panes. loss and heat gain, while others questions coming into county In the summertime, water dripping have caulked and weatherstripped offices about moisture and water- from toilet tanks and cold water pipes around windows and doors to related problems in the home. and condensation on masonry or reduce the infiltration of cold air The complaints occur in both stone surfaces in basements are the into their homes. The same winter and summer, and they take major causes of frustration. a variety of forms. practices that trap heat in the Some homeowners complain home also trap high levels of about water and ice formation on Causes of moisture. interior windows in winter. Others Condensation complain about peeling exterior A second common condition paint and the growth of mildew All air contains water in the gaseous contributing to moisture problems and mold inside the home. Still or vapor form. The temperature of in Michigan homes is the existence other homeowners report the air determines how much water of cool surfaces with which interior frustration over water collecting in vapor it can hold. As air gets moisture vapor naturally comes in basements or crawl spaces. warmer, its capacity for holding water contact. This problem often occurs Resulting odors and concerns vapor increases. On the other hand, in the homes of people who have about structural damage that as air cools, its capacity for holding not insulated or weatherized. In could occur and the hard work water vapor decreases. When air less energy efficient homes, and expense needed to clean and cools and its vapor-holding capacity certain locations are prime repair any damage are major decreases and the amount of vapor candidates for condensation concerns. in the air stays the same, the air may problems because they commonly All of these problems involve one eventually reach or exceed its have cool surfaces. These include or more of the three most saturation level. At this saturation poorly weatherized and insulated common types of moisture point, the excess vapor from the windows (in winter), poorly problems in Michigan homes: air insulated exterior walls and condensation, seepage and will begin condensing and collect ceilings (winter), masonry or concrete surfaces (summer), toilet tanks (summer) and cold water pipes (summer). second alternative available to covering the ground, crawl spaces A third condition contributing to lower should be provided with adequate household condensation problems summer time humidity levels is to natural ventilation to facilitate air is excessively high humidity levels purchase and operate a movement throughout the space. in the air within the home. Humidity dehumidifier. If a vapor retarder is present in levels are expressed as percentages If humidity levels remain high in the crawl space, 1 square foot of and can be measured somewhat winter, you may need to run it free vent area is required for accurately with inexpensive gauges then, every 1,500 square feet of crawl purchased at local hardware stores. too. A dehumidifier uses space ground area. Without a The normal indoor humidity range in mechanical vapor retarder present, 1 winter is 15 to 50 percent. In the means to provide a cool surface square foot of free vent area is summer, the humidity range may be where condensation can occur. A required for every 150 square higher because of the higher outdoor container located below the feet of crawl space ground area. humidity levels we sometimes condensation coils catches and Most crawl space vents include experience then. collects the condensed water for louvers and/or screens to prevent eventual disposal down a drain. the entry of insects and small High Humidity Level Problems Though both air conditioners and animals. These coverings slow Because high household humidity dehumidifiers are effective air circulation and cut down on levels can cause problems in both solutions to excessive moisture the vent's effectiveness. Thus, energy-efficient and less energy- problems, they are relatively you will need to double the efficient homes, the first step to be expensive to buy and costly to amount of ventilation needed taken in attempting to control operate. Expect increases in your in most cases to compensate condensation problems is simply electricity bills during the months for this reduction. For example, to reduce the level of humidity in you use them. a 1,500 square foot crawl space the inside air. would require 1 square foot of During the winter, the humidity level Houses on Crawl Spaces ! free you will want to attempt to achieve in In homes built on crawl spaces, vent area if a vapor retarder was your home will depend on the outside evaporation of moisture from the present on the ground. If the vents temperature. As outside temperatures earth is a major source of used had screens or louvers, 2 drop, you need to lower inside relative household humidity The high square feet of vent area would be humidity levels to minimize levels of humidity in crawl spaces needed to vent the crawl space condensation (see Table 1). Monitor can be a problem in both summer adequately. Locate vents near the interior surfaces of double pane and winter. Foul odors in the corners and across from one windows during winter. If running home or crawl space, mold and another to facilitate air movement water (condensation) is apparent on mildew growth in the interior of through the crawl space. them, the interior relative humidity the home (especially in closets) level is too high and should be and growth of fungi in the crawl Attic Ventilation ! lowered. Levels to achieve in summer space itself are signs of the Adequate natural ventilation is are somewhat more arbitrary-they problem. Covering the crawl important in the attics of homes as depend mainly on how uncomfortable space ground with a vapor well. If a vapor retarder is not you are in high humidity conditions. retarder (polyethylene or heavy present in the ceiling to slow plastic sheets available at migration of moisture from the Summer Problems ! lumberyards) is crucial in home's interior into the attic, attics During the summer, one of the major preventing moisture problems in require 1 square foot of free vent functions of an air conditioner, in crawl space homes (see Fig. 1). area for each 150 square feet of addition to cooling warm interior air, is attic area. removing humidity from the In addition to a vapor retarder home. A An exception occurs when the problems for attic vents are located in a homeowners: humidifiers, new construction or, remodeling, and high/low configuration (i.e., half of malfunctioning combustion appliances. the vent area in the eave/soffit area and the other half in the roof Humidifiers ridge area). In that case, 1 square foot for each 300 square feet is Many homeowners use humidifiers to add moisture to their homes in winter. adequate. If a vapor retarder is In the past, when homes were leaky and so less energy efficient, much of the present in the ceiling, attics moisture generated inside the home went out with the warm air escaping require 1 square foot of free vent around and through windows and doors. area for each 300 square feet of attic area. Overly dry air was common, and people experienced static electricity buildup on carpets and clothes, breathing difficulties due to, dry, nasal passages and A number of types of vents are somewhat destructive overdrying of furniture. To combat this dryness, they available to provide attic commonly used humidifiers. Some were incorporated directly into forced air ventilation (see Fig. 2), As with heating systems, and moisture was circulated in the home along with heated crawl space vents, most include air. A second type of humidifier, the free-standing model, is portable and can louvers or screens to prevent the be. moved freely around the home to provide moisture where it is most entry of insects and rodents, and needed. Whether you have extensively weatherized your home or not, these coverings slow air experiencing condensation problems means you should not use a humidifier. circulation. Therefore, twice the amount of ventilation is needed in most cases to compensate for this Construction Moisture reduction. For example, a 1,500 square foot attic would normally Homeowners who move into a newly constructed home or complete require 10 square feet of vent remodeling projects often experience high moisture levels in the interior as area if a vapor retarder was not the building materials and systems dry. If it is necessary to close the house present in the ceiling assembly. If because of cold weather, the problem may seem excessively serious. Over the vents used had screens and time, the building materials will dry and a form of equilibrium will be louvers, 20 square feet of vent established.