The National Building Code of Canada (NBC) requires glazing in certain applications in educational facilities to be fire-rated. Today’s advanced fire-rated glazing products make it possible to do significantly more than protect against the spread of fire.
For the past 100 years, developers and architects driven by the Modern movement have designed skeletal boxes skinned with glass for beauty and simplicity. Natural light, the diminishing of separation between interior and exterior, and open working environments were the result of these experimental glazing assemblies. This strategy continues to spread throughout the globe, in all climates.
In many large, urban areas of Canada, most of the population lives in apartment buildings. In the downtown core of cities like Toronto, the proportion is up to 70 per cent. With the current trend to intensify urban areas to limit sprawl into surrounding valuable farmland, the proportion of high-rise multi-family dwellers is expected to increase.
Today, more and more architects are literally thinking outside the box. Modern buildings are taking on unique shapes and forms, and structures are reaching staggering new heights. This shift means the purpose of the building envelope is also expanding.
One of the strategies employed by architects to increase (or regain lost) glazing area to meet the performance objectives of building energy codes and standards involves using established building envelope elements such as window louvres, fins, and shelves, along with emerging technologies such as vacuum-insulated glazing and panels (VIGs) and electrochromic (EC) glass.
For decades, the words ‘design flexibility’ and ‘fire-rated glass’ would not have appeared in the same sentence. Traditional polished wired glass was the only glazing material permitted in fire-rated areas. Its network of wires holds together broken glass during a fire to slow the spread of flames and smoke longer than was previously possible with other available glazing products.
The building industry consumes 40 per cent of the world’s energy, and is responsible for more than 38 per cent of greenhouse gas (GHG) emissions, according to studies completed by the World Business Council for Sustainable Development (WBCSD 2009). The energy demand and its costs will continue to increase; this explains why Canadian building code requirements are becoming more stringent.
Glazing is an integral part of modern design. From a thermal standpoint, glazing and its structure or frame is the weakest point of a wall assembly.1 A double-glazed vinyl window with argon’s U-factor (i.e. thermal transmittance) is typically around 3 W/(m2 K). This means the window will gain or lose around 3 W per m2 per degree Celsius. An efficient fibreglass window system’s U-factor can be as low as 1 W/(m2 K). An aluminum curtain wall system can range as high as 4 W/(m2 K). On the other hand, the U-factor of a 152-mm (6-in.) steel stud, with batt and exterior continuous insulation, can be around 0.4 W/(m2 K).