3.6 Insulation Safety and Durability
Insulation activities require awareness about safety. Reference the following safety-related sections of this guide if necessary.
ü See “Asbestos Containing Materials (ACM)” on page 38.
ü See “Decommissioning Knob-and-Tube Wiring” on page 43.
ü See “Respiratory Health” on page 50.
The following fire-safety and durability issues are particularly important to installing foam insulation.
• Foam insulation requires a thermal barrier covering of at least half-inch drywall when installed in a living space.
• Foam may require an ignition barrier when installed in attics or crawl spaces or it may not.
• A thermal barrier is a material, usually drywall, that protects combustible materials behind it from heat and flame creating a fire.
• An ignition barrier is designed to delay the ignition of the material it protects. Ignition barriers include plywood, galvanized steel, damp-spray fiberglass, and intumescent paint. Intumescent paint is a proprietary latex coating designed to delay the ignition of foam insulation in a fire.
Moisture is the most common and severe durability problem in insulated building assemblies. Moisture fosters rot by insects and microbes. Entrained moisture reduces the thermal resistance of many insulation materials. Moisture affects the chemistry of some building materials: metals for example.
Moisture prevention includes denying moisture access to building cavities, allowing condensed water to drain out, and allowing moisture to dry to the indoors, outdoors, or both.
Retrofitting insulation can affect the preventive measures listed here. Consider the function and relevance of these building components whenever you install insulation.
• Air barrier: Air can carry moisture into building cavities from indoors or outdoors where the moisture can condense and dampen insulation and other building materials. Air leakage is an energy problem too. The air barrier is any continuous material or building assembly that provides acceptable resistance to air leakage.
• Vapor retarder: Vapor diffusion can carry large amounts of water vapor into building cavities where it can condense and dampen insulation and other building materials. Vapor retarders resist water vapor diffusion from indoors into cavities where condensation can dampen insulation and other building materials.
• Ground-moisture barrier: The ground under a building is the most potent source of moisture in many buildings, especially those built on crawl spaces. Most crawl spaces require ground-moisture barriers to prevent the ground from being a major cause of moisture problems.
• Water resistive barrier (WRB): Asphalt paper or house wrap, under siding and roofing, serves as the home’s last defense to wind-driven rain, which can dampen sheathing and other building materials. This water resistive barrier must be protected during insulation and incorporated into window openings during window replacement.
• Vapor permeable materials: Most common building materials are permeable to water vapor, which allows the water vapor to follow a gradient from wet to dry. This process allows building assembles to dry out to both indoors and outdoors. Vapor permeable materials are essential for fail-safe building assemblies in most climates.
• Flashings: Seams and penetrations in building assemblies are protected by flashings, which prevent water from entering these vulnerable areas.
• Drainage features: Intentional or unintentional drainage features of buildings allow water to drain out of cavities. Examples: Masonry veneers have intentional drainage planes and weep openings near their bottoms. Cathedral ceilings drain water out through their soffit vents unintentionally.
• Water storage: Masonry veneers and structural masonry walls have the ability to store rainwater and dry out during dry weather.
• Ventilation: Roofs, attics, crawl spaces and even some walls have ventilation features that dry out wet building assemblies.
• Termiticide: When foam insulation is installed below grade in regions with termites, apply a termiticide to the soil in amounts determined by the labeling of the termiticide.
Consult with experts when necessary to preserve, protect, or install these moisture-prevention features, according to local climate and established best practices.