Fenestration Forum: February 2014
By Brian Burton
Changing with change
By Brian Burton
Engineers Canada has established a committee to examine the
vulnerability of buildings to global climate change, defining it as any
systematic change in long-term statistics of climate elements sustained
over several decades or longer.
Engineers Canada has established a committee to examine the vulnerability of buildings to global climate change, defining it as any systematic change in long-term statistics of climate elements sustained over several decades or longer. Building envelopes have become thinner and lighter with evolving construction materials and systems and are especially susceptible to even minor changes in weather patterns.
Cities, with their high density of buildings, are particularly vulnerable to extreme weather events and premature deterioration of building enclosure systems. The foremost concern involves the health, safety and well-being of occupants. Canadians spend over 90 per cent of their time indoors. In addition to temperature extremes, occupants can be adversely affected by changes in humidity levels and by the presence of chemicals, pollutants and/or mould. Building enclosure systems are also in direct contact with the elements. As such, the envelope serves an important function as an environmental separator between the outside elements and interior conditions.
For existing buildings, the age and condition of the structure, the materials used in its construction and the type of building envelope system can influence its ability to resist the forces of climate change. For example, a 50-year-old masonry building constructed using a face-sealed cladding system will have very little capacity to resist the impact of climate change because the shell of the building is directly exposed to the ever-changing and increasingly hostile exterior environmental conditions. In buildings that incorporate pressure-equalized rainscreen walls, the primary environmental separators are concealed and less exposed to the elements.
Several climate change factors may have a direct impact on the building envelope. Higher solar intensity causes higher exterior and interior surface temperatures.
Some areas may see shifts the in the form and intensity of precipitation, including an increase in instances of melting permafrost, freezing rain and rain on snow. Shifts in the peaks and frequency of high humidity levels can be harmful, as can changes in the seasonal range of temperatures combined with increased frequency and longevity of heat waves or cold snaps. These changes in temperature and the forms of precipitation acting on the enclosure systems can lead to dimensional changes of materials which in turn can lead to cracking and fissuring in polymer-based materials such as vinyl cladding, window frames, sealants and gaskets.
Other environmental factors that may be indirectly exacerbated by climate change include increases in dust and other airborne particulate matter, acid rain, UV radiation, wind-driven dust mixed with rain, and rain.
Biological agents carried by the atmosphere can deposit fungi or moulds on surfaces while chemical agents transported by atmospheric moisture or by direct deposition can lead to corrosion in metals or deterioration of concrete, stone and fenestration components. Climate change also creates uncertainty that may undermine the meteorological data we use to design our buildings.
It is a relatively straightforward exercise to simulate at least some of the impacts of various climate change scenarios on full-scale mock-ups of building envelope assemblies in laboratory settings. These strategies might assist in determining what changes in design, building codes and building practice could mitigate these impacts.
Brian Burton is a business development consultant and is serving on the Personnel Committee for the CSA’s Certification Program for Fenestration Installation Technicians. You can contact him at firstname.lastname@example.org or visit his new website at http://burtons-pen.com