Airtightness requirements
In addition to the thermal characteristics of wall assemblies, critical consideration must be given to airtightness. Sections 3.2.4, Air Leakage, and 3.2.4.2, Opaque Building Assemblies, of the NECB require all opaque building assemblies to include an air barrier.
An integral part of EIFS is the liquid-applied air- and water-resistive barrier (WRB). Although this is not a requirement of either the Canadian Construction Materials Centre’s CCMC Technical Guide (The Technical Guide for Exterior Insulation and Finish Systems [EIFS] was published by the National Research Council of Canada [NRC] in 2006) or the Underwriters Laboratories of Canada (ULC) CAN/ULC-S716.1, Standard for Exterior Insulation and Finish Systems (EIFS) – Materials and Systems, many EIFS manufacturers test their WRB for airtightness properties—another feature of EIFS that, when designed and installed as a high-performance cladding system, easily surpasses the requirements of the the NECB in all Canadian climate zones. (For properties and test results of specific WRBs, it is best to consult the manufacturer.)
A key consideration for air barriers is the interconnection of the planes of airtightness from roofs to walls, walls to fenestration/doors, and walls to below-grade foundations. A robust design requires a would-be builder to manage the transition of materials and trade contractors at every interface of a building’s envelope. Air leakage testing for building commissioning is a growing method of validating building performance. (For information on standards for airtightness testing, visit the National Air Barrier Association at www.naba.ca and the Air Barrier Association of America at www.airbarrier.org/whole_building/index_e.php.) Though this testing was first devised as a method of certifying R-2000 homes in the 1980s, recent developments in Canada Green Building Council (CaGBC) and U.S. Green Building Council (USGBC) circles, ASHRAE, and building science consultants are working toward standardizing methods and processes as part of the evolving business of commissioning building envelopes for commercial, institutional, and multi-residential projects. (This information was taken from the “Building Science Roundtable” in February 2016, edited by Ted Kesik.)
Meeting code requirements with EIFS
Stretch codes are pushing the minimum requirements for building energy performance, meaning thermal performance is increasing. (Upcoming code changes can be viewed at www.nrc-cnrc.gc.ca/eng/solutions/advisory/codes_centre/public_review/summary.html.) Concurrent to code evolution, understanding and accounting for thermal bridging is becoming commonplace. Building designers specifying EIFS as a high-performance cladding solution can meet the NECB more effectively, economically, and ecologically than with other cladding choices. (More information can be found in “Sustainable Cladding Choice Equates to High-performance Building Envelopes,” an article released in Construction Canada’s January 2016 issue. It can be found at www.constructioncanada.net/sustainable-cladding-choice-equates-to-high-performance-building-envelopes.)
As summarized by Edgar, a truly continuous insulation improves the longevity and performance of the building by eliminating thermal bridging and, therefore, also condensation, air movement, and building movement induced by thermal shock. A high-performance, EIFS-clad wall assembly incorporates an integrated air barrier, and where an increased window-to-wall ratio may be needed, EIFS’ insulation thickness can be increased to accommodate. EIFS has the additional advantage of providing distinct exterior finishes, which can be made to look like masonry, stone, metal, or other appearances while providing the benefits of CI with an air barrier. EIFS is CI, and lacks thermal bridging. Combined with its versatile appearance and service life of 50 or more years, this makes it invaluable in meeting the requirements of the country’s energy codes.
Amanda Sinnige is the manager of technical services for Dryvit Systems Canada, having joined the company in early 2015. She has worked in the field of building science for the past 26 years, concentrating her efforts on the energy performance of buildings, sustainable construction and renewable energy, and the impact of these on the performance of the building envelope. She can be reached via e-mail at ajsinnige@dryvit.ca.
Kevin Day, LEED AP, is the vice-president of sales and marketing for Dryvit Systems Canada. He is the chair (and past-president) of the Exterior Insulation and Finish Systems (EIFS) Council of Canada, and a past-president of the Ontario Building Envelope Council (OBEC), winning its 2014 Anthony A. Woods Award. Day is regarded as a leading expert on EIFS, and is widely recognized for his extensive cladding engineering experience. He is a frequent contributor to Construction Canada. He can be reached at kcday@dryvit.ca.
