Roofs, and particularly flat ones, face unique issues when dealing with sudden downpours. Builders are discovering sprayed polyurethane foam (SPF) can contend with the ‘new normal’ extreme weather that is being witnessed.
Use of two-pound, medium-density closed-cell sprayed polyurethane foam (SPF) is growing rapidly in commercial structures. Utilization of the material has been fuelled in large part by its ability to seal the structure and, in doing so, tremendously enhance energy efficiency.
Unvented attics have been designed and constructed for some 30 years. They are referred to by various names, including conditioned attics, semi-conditioned attics, indirectly conditioned attics, hot roofs, and compact roofs.
With varying degrees of detail and prescription, Canadian building codes—regardless of the model code—require all buildings to be provided with an air barrier. Where the language is more performance-oriented, such as in Part 5 of the National Building Code of Canada (NBC) and Part 3 of the National Energy Code of Canada for Buildings (NECB), key concepts such as “system” and “continuity” are introduced as well as quantitative criteria.
Reducing the operational energy use and increasing durability should be the prime concerns of architects who wish to design and build ‘green’ buildings,” wrote John Straube, PhD, P.Eng., principal at RDH Building Science and RDH Building Science Labs.
In Canada, products approved for use as a thermal barrier for foamed plastic must pass either CAN4-S124-M, Standard Method of Test for the Evaluation of Protective Coverings for Foamed Plastics, or CAN/ULC-S101, Standard Methods of Fire Endurance Tests of Building Construction and Materials, to comply with the National Building Code of Canada (NBC).
For decades, designers of attics and crawlspaces have used cross-ventilation to minimize potential for moisture accumulation and condensation. However, spurred by recent claims of energy savings and moisture control, unvented attics have become popular in both residential and commercial applications. While these attics can be used in many circumstances, this author believes there are reasons to use vented assemblies in many situations.
The effective specification and installation of all types of thermal insulation requires an understanding of the factors affecting performance. The specification of a thermal resistance (RSI or R-value) alone does not ensure the intended heat-flow reduction.
A focus on green building standards and more stringent code requirements has led to adoption of best practices in construction materials and methods. Among those is specifying more efficient insulation systems, air barriers, and seamless monolithic roofing assemblies. Use of closed-cell sprayed polyurethane foam (ccSPF) can help meet the stringent requirements of modern, sustainable building design.