In winter months, they can be spotted throughout the northern regions of the United States. At first they might seem harmless. Some even sparkle as the winter sun reflects from the stalactite-like structures. They are ice dams, and these giant icicles are surefire predictors of damned indoor air quality.
Ice dams are caused when the temperature on the upper part of a roof is warmer than on the lower edges. The melting snow freezes at the colder lower edges, creating dams in the eaves troughs (gutters). Problems start when the dammed ice begins to melt, and water backs up under shingles, seeking the paths of least resistance.
Water that backs up under shingles and runs into the attic, insulation, walls, and ceilings often remains undetected. However, hidden within the wet cavities are feeding frenzies for mold and other nasty microorganisms. Sustained moisture causes structural damage, odors, and biological growth.
Consequences of Dammed Ice In most regions of the US, ice dams melt before March, and signs of water damage begin to appear. Some indicators of water damage from ice damming include:
• Curling and cupping of shingles
• Stains on ceilings and walls
• Stains on the underside of a roof deck
• Mold growth on wood structures in the attic
• Drip stains on insulation in the attic
• Oxidized nails on the underside of a roof deck
• Musty or mold type odors
If signs of damage from ice damming are discovered, a qualified professional should be called upon to evaluate structural damage, assess mold growth, and develop a safe remediation plan. A qualified consultant will not only provide recommendations for addressing visible mold and water damage, but will also identify areas that should be evaluated for hidden damage. To prevent cross-contamination during invasive investigations into suspect cavities, personal protection, HEPA-filtration, and partition barriers should be used. An ounce of prevention is priceless when hidden mold contamination is found, especially in a home with immune compromised individuals.
Effective remediation involves two components: (1) removal of the mold and (2) addressing spores in the air and on surfaces. Removal of attic mold caused by ice damming typically requires removal of the affected roof decking, as the growth is not limited to visible surfaces. Trusses, joists, and other wood roof members can usually be cleaned using some type of abrasive cleaning. One of the best abrasive cleaning methods for attics is dry ice blasting. This method is not only less labor intensive than sanding or scrubbing, it is more effective because the dry ice freezes the surface of the moldy substrate. Dry ice blasting also facilitates cleaning of crevices and hard to reach areas. As with all mold remediation, appropriate containment measures, personal protection, and engineering controls must be employed.
Remediation after ice damming generally requires removal of the attic insulation. Insulation that is directly impacted by water loses its efficiency. Insulation in proximityof mold growth must be removed because of cross-contamination. Aerosolizing of mold spores, fragments and other propagules that settle onto insulation can cause adverse health effects. After insulation is removed from an attic, surfaces must be cleaned to remove particulate debris and settled spores.
Removal of attic insulation also allows for a thorough inspection of the topsides of drywall ceilings. Assessment of staining patterns can provide clues about areas of potential hidden water intrusion into wall cavities. Drywall with visible mold growth on the topside of ceilings must be removed under appropriate containment.
Appropriate mold remediation after ice damming is necessary to protect the air quality within an indoor environment and prevent structural damage. Re-construction after remediation must be executed in a manner to correct the conditions that caused ice damming in the first place. The most common approaches to preventing dammed ice involve installation of appropriate insulation, ventilation and vapor barriers. Roofing contractors should provide warranties and be held accountable for these issues.