Moisture Problems Associated with Windows
By far the biggest health concern involving windows occurs when they fail to do their job properly. This job is to let in natural light and allow for ventilation while keeping water out. Windows have drainage channels that are designed to shed water away from the building, but if these are not working properly they can channel water into the building cavity, causing serious water damage.
A simple testing procedure can determine if the windows themselves are shedding water properly (see Division 13 for window testing). Windows can be faulty because of manufacturing defects, mishandling during transport, or improper installation. Windows have a structural weak point where the sill is screwed into the jamb. The seal can break during handling and the tiny gaps can go undetected. Some window manufacturers have added a neoprene gasket at this juncture to make it more secure. If the juncture between the window and the wall contains gaps resulting from incomplete or incorrect application of sealing, air will travel through the gaps. When that air sheds moisture because of temperature differentials, condensation can accumulate. Proper sealing is discussed in the section on insulation around doors and windows in Division 7.
Improper head, jamb, and sill flashing can also result in water finding its way into the wall cavity. (For appropriate flashing materials, see the section in Division 7 on water management at doors and windows.) These water intrusions, which are not readily detectable in the completed building, can eventually lead to structural deterioration and mold problems. In the section on testing for weathertightness in Division 13, we discuss a test that can help determine if there are any installation faults that can lead to future water damage. This test can be performed at a time in the construction when faults can still be easily and inexpensively corrected. All of these potential problems related to windows are exacerbated if the wall cavity does not have a means of drying out once it gets wet.
Because the quality control testing procedures we have referred to are not standard for most residential construction companies, it is unlikely they will be performed unless you specify them in your construction documents. These measures will take a little extra time but can potentially extend the life of a building for many years and prevent mold problems that could be devastating to your health.
Wood windows are routinely dipped in a waterborne fungicide. Unlike wood doors, it can be cost prohibitive to have operable windows custom made. Chemically sensitive individuals will often choose steel or aluminum windows with a baked-on enamel finish to avoid exposure to the fungicide as well as to the ter — penes from pine frames. Wood windows can be sealed to avoid these exposures. You may wish to specify the following: [14] [15]
the section on clear vapor-barrier sealants for wood in Division 9.
• Where a painted finish is scheduled, use a primer paint that seals in VOCs, as specified in the section on paints in Division 9.
Most wood window manufacturers also produce clad windows, which have wood on the inside and aluminum, steel, or fiberglass coating on the outside for weather protection. The cladding provides UV protection so that it is unnecessary to apply protective coatings on the window exterior. If unclad windows are used, you will need to do yearly maintenance consisting of staining and sealing in order to protect the window frames from the elements.
The following products do not contain many of the toxic substances commonly found in exterior wood finishing products and can be used for the preservation of wood window frames and doors:
• AFM Safecoat DuroStain: Wood stain
• Auro Natural Wood Stain No. 160: Colorless and color finish, good weather resistance
• BioShield Aqua Resin Stain: Weather — resistant wood finish with ultraviolet protection
• BioShield Primer Oil #1: Undercoat; use finish coat of Livos Kaldet Stain or Livos Vindo Enamel Paint
• OS Color One Coat Only: Weather — and UV-resistant, water-repellent, semitransparent wood stains
• Weather Pro: Water-based, water-repellent wood stain
Weatherstripping is used around doors to make them airtight and resistant to water leakage. Weatherstripping can also be specified around interior doors where noise or odor control is desired. Most available weatherstrips are made of synthetics, including silicone, urethane foam, polypropylene nylon, and neoprene. Some will outgas. Neoprene, for example, can have a strong odor. Brass and stainless steel weatherstripping are available at many hardware stores. Choose the least odorous weatherstripping that accomplishes the job.
As mentioned earlier, when planning a healthy home the garage and mechanical room should be designed so they do not open directly to the interior because they will introduce harmful byproducts of combustion and odors into the home. A simple breezeway can provide weather protection between a detached garage and the home. However, doors and common walls between home and garage are found in almost all new housing because many people find a detached garage to be an unacceptable inconvenience. Where a door to the garage or mechanical room opens into the living space, it is important to specify that these doors have a threshold sealed with an acceptable sealant. The doors should be fully weatherstripped to prevent harmful fumes from entering the living space through the door openings. In fact, the entire common wall between the home and the garage should be made airtight so that fumes do not seep through the wall from the garage into the home. For the specifics on creating this airtight wall, refer to Division 9.
