By William Pyznar P.E. & Andrew Amorosi, P.E., R.S.
Community associations, building owners, engineers, contractors and property managers deal with the constant battle of keeping water out of the building envelope, but sometimes the water that causes stains, mold and decay actually originate from within the building envelope. The cold temperatures of the winter months combined with specific interior conditions can result in excessive condensation and even bursting pipes.
Condensation may be in the attic, basement and crawl spaces or inside wall cavities. Deficiencies in the original construction or recent reconstruction of exterior wall cavities, basements, crawl spaces, roofs and/or attics can exacerbate the conditions resulting in excessive condensation conditions and potential for damage and mold development. Sometimes, the conditions may be seen, but many times, the conditions and subsequent damages may be hidden from view and worsen with each passing winter season, escalating repair costs.
Condensation will also form on cold surfaces (such as single window panes and aluminum window frames with no thermal break or un-insulated walls) as warmer moisture saturated air contacts the cold surface, causing the air that is in contact with the window to cool. These conditions can also result in damage to insulation, structural components, or interior finishes and mold growth.
Aside from proper construction methods and materials, the most essential aspect of preventing moisture damage to a building from condensation is to keep indoor relative humidity at effective levels during the winter season. Humidity levels consistently below 30% may cause respiratory problems and shrinking of wood furniture, flooring or trim. Readings of 30% or higher appear to prevent or certainly reduce these problems; however, higher humidity levels begin to create the potential for condensation build-up.
When indoor heat and humidity become elevated during the winter season, condensation conditions begin to appear. It is difficult, even with proper wall construction and vapor retarders, to construct a building that will not have condensation problems when indoor humidity exceeds 40 or 50 percent without incorporating special design aspects of mechanical equipment including de-humidification; however, lack of proper construction can result in major problems.
Normal household activities such as cooking, showering or bathing, washing clothes and dishes, drying clothes, even breathing and perspiring can raise the humidity levels in a home. A typical family of four converts three gallons of water into water vapor per day. It takes only about six pints of water to raise the relative humidity of a 1,000 sq. ft. home from 15 to 60 percent. Therefore, any excess of the activities listed above can elevate the moisture in the air even more.
To reduce the potential for condensation and avoid the problems of excess moisture, it is necessary to limit or control the amount of water vapor in the house. This can be accomplished by modifying lifestyle activities and/or by using mechanical means such as exhaust fans or dehumidifiers.
To reduce moisture vapor production within the home, the following can be implemented:
- Decrease shower time.
- Maintain heat at 68 degrees F and not higher.
- Avoid boiling water or liquids excessively.
- Limit clothes washing to full loads.
- Open blinds and drapes so that air can circulate freely over the windows.
- Do not hang wet clothes inside the home.
- Move furniture such as sofas and bookcases so they are not touching outside walls. This will improve air circulation around the cooler, outside, wall and reduce condensation potential.
- Open windows a bit to allow moisture to escape and promote air movement as well when cooking.
- Install properly sized dehumidifier(s).
Similarly, bursting pipes in the winter may be a result of deficient construction. Lack of insulation, or the location or penetrations of the pipes through walls are main factors in this condition.
Ensure that pipes are in heated spaces and/or properly insulated.
Look for areas where water supply lines are located in unheated areas. Look in the basement, crawl space, attic, garage, and under kitchen and bathroom cabinets. Both hot and cold-water pipes in these areas should be insulated.
Install products made to insulate water pipes like a pipe insulation sleeve or heat tape on exposed water pipes as needed.
Keep garage doors closed if there are water supply lines in the garage.
Allow a cold-water drip from the faucet served by cold exposed pipes, running water through the pipe (even at a trickle) – may prevent pipes from freezing by allowing air to escape.
Building codes address the amount of insulation to be used and the use of vapor barriers and vapor retarders; however, specific design analysis is not a requirement. While building codes also address ventilation and moisture control in general terms, they lack specifics with regard to varying construction or conditions. It is critical that each specific condition be properly analyzed.
In general terms, the following information typically applies to Northeast construction:
As the most basic and general rule, a vapor retarder should be installed on the warm side of the insulation during new construction or during significant rehab projects. This vapor retarder will limit the amount of interior water vapor that passes into the wall cavity. This is typically accomplished by installing paper faced insulation upon original construction. Although not a code deficiency, the paper backing on typical blanket insulation is technically a vapor retarder, but the ends do not overlap each other over the edge of the studs for it to be completely effective. It is also difficult to provide coverage of wall, window and door framing with this type of vapor retarder. A more effective vapor coverage may be the installation of wide sheets of polyethylene inside the wall with precise cutouts for windows and outlets.
Locations of water pipes and penetrations in cold spaces should be properly insulated. The design professional should analyze the wall cavity to determine whether the assembly is susceptible to condensation. There are many variables that affect this potential: 1.) Different systems will react differently and need to be investigated to ensure that they are proper. 2.) The types of materials and their respective R-values, permeability ratings, thickness as and even locations within the cavity are all factors that can affect the potential for excessive condensation to occur. 3.) The size, type and layout of the interior environment are also factors that should be considered.
A change in any of these variables can affect the potential for condensation build-up dramatically. For example, a change in a building façade from vinyl siding to a stucco system may create future condensation problems if the above discussed variables are not analyzed. Additional vapor barriers or other products may be necessary, and should be considered.
Attics should be properly vented and insulated. The temperature of the attic space should be consistent with the exterior temperature. Flat roofs may require a similar analysis as with walls as discussed above.
Crawl spaces should be properly vented including as needed exhaust fans and/or sump pump systems to reduce moisture and protect framing. Water pipes in these spaces should be properly protected and may require heat devices.
Dehumidifiers and proper wall cavity construction are needed if finished space is desired. The construction, use and maintenance of a building can have significant impact on the humidity levels and condensation issues that may occur. Condensation was not much of a problem in pre-WWII construction, as the ‘loose’ or inefficient energy construction allowed for the flow of air and humidity in and out of the building. With new, more efficient, construction methods, and more appliances and living habits that encourage or increase the release of water vapor into the home, condensation has become more prevalent and the damages and mold growth that go along with continued wetting have become an issue.
It is important to properly evaluate an existing condensation or water pipe break condition to ensure the problems are not solely weather related.
William Pyznar, P.E. and Andrew Amorosi, P.E., R.S. are principals of The Falcon Group with headquarters in Bridgewater, New Jersey.