In the midst of a record-breaking year for Atlantic hurricanes in the U.S., Icynene, Inc., the manufacturer of The Icynene Insulation System, initiated a study last fall to evaluate insulating practices that can protect homes and their occupants from water and moisture damage resulting from high winds.
Based in Toronto, Icynene, Inc. is a member of the National Council of the Housing Industry — The Supplier 100 of NAHB.
The study was conducted by the Alan G. Davenport Wind Engineering Group at The University of Western Ontario, using a model home with reduced air infiltration rates similar to those that would be achieved in a home insulated with Icynene’s insulation/air barrier system.
The model created for the test was a gable-roof house with the attic and living space scaled to maintain similar volume ratios to those of a full-scale home. Two different insulation applications were tested to determine which would perform better in strong winds. Wind climate models for Chicago and Miami were used during the tests.
In the first test of a typical vented attic design, wind and the laterally-driven rain accompanying it entered the attic through the soffit vent assemblies, which under real conditions can cause flooding and an increased risk of mold growth and rotting building materials.
Studying the rainwater performance of residential assemblies in Central Florida during hurricanes in 2004, building science expert, Joe Lstiburek of Building Science Corporation, concluded that “soffit geometries are currently not designed to address extreme wind-driven rain exposures.”
In the second batch of tests, all of the soffit vents were sealed, creating an unvented sealed attic assembly, which is an approach recommended by Lstiburek and other experts to prevent rain from entering. With this approach, the attic becomes part of the conditioned space.
The testing found that sealing the soffits eliminated the entry of moisture into the attic, helping to prevent moisture damage to the insulation and ceiling materials. “This technology has significant advantages in the Florida climate with respect to rainwater control, energy conservation, moisture and humidity control, wind uplift and fire performance over standard attic roof technology” Lstiburek’s study found.
Icynene is one of the few insulation products that are approved for use in this type of application, according to its manufacturer. The material is able to create a complete air-seal, which reduces airflow and accompanying moisture in and out of the building envelope. Because of this product’s proven performance in unvented conditioned attics, it has been the insulation of choice for high-profile demonstration projects that feature this design, Icynene says.
The International Code Council recently approved amendments to its International Energy Conservation Code and International Residential Code that approve unvented conditioned attic assemblies, stipulating that an air-impermeable insulation can be applied directly to the underside or interior roof deck, according to the manufacturer.
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