Due to their light weight per unit area, steel roofs can provide structural savings in buildings when compared with heavier non-metal roofing alternatives. For reroofing projects, steel roofing can often be applied over the non-metal roof, saving removal and disposal costs. Above all, steel roofing systems provide significant advantages in reduced energy use and overall sustainability.

Buildings consume two-thirds of all electricity produced and one-third of all energy produced in North America. While it is recognized that adding insulation under the roof surface can reduce cooling and heating costs, there is a diminishing return on the strategy of increasing insulation to conserve energy costs. This is where ‘cool roofing’ can play roles in further reducing the energy consumed and in minimizing the heat island effect created in large urban areas.

Steel roofing materials are available in a variety of finishes, colours, textures, and roofing profiles, with varying levels of reflectivity and emissivity to fit building needs in a wide range of regions and climates. Reflectivity is the ability of a roof to reflect solar radiation back into the atmosphere, preventing it from being absorbed into the building envelope and reducing the need for energy to cool the building. Emissivity is the ability to emit absorbed solar infrared radiation back to the atmosphere.

Since much of Canada has long, cold winters, this time of year’s ‘heating load’ conditions generally have a greater influence on energy consumption than the summer’s ‘cooling load’ when analyzed over the course of a full year. The degree of influence depends primarily on the geographic location, the insulation level in the roof assembly, and the cost of energy. For example, heating loads in Winnipeg are much higher than in Windsor, Ont., because of the former’s greater number of heating degree days. These climate factors require building professionals to consider materials with different reflectivity and emissivity properties than their colleagues working on projects in warmer climates such as the southern United States.

Calculations involving solar reflectance and emittance can be used to determine the energy savings attributable to a roof. Steel roofing can reduce energy costs associated with air-conditioning. For cooling loads, it is advantageous to reflect as much solar radiation as possible, and to re-emit as much of the absorbed infrared radiation as possible. However, for energy savings associated with heating loads, absorption of solar infrared radiation is beneficial; it is best to retain absorbed solar radiation rather than emit it back into the atmosphere.

In other words, for colder Canadian climates, it is best to have roofing products with high reflectivity and low emissivity. Metallic coated steels, such as Galvalume Plus (i.e. 55 per cent aluminum-zinc) combine these properties, making them the best option for low-slope roofs in Canada.

In addition to their energy-saving benefits, steel roofs can contribute to a building’s use of renewable energy. They provide the optimal foundation for photovoltaic (PV) installations since the roof can be expected to last longer than the solar system it supports. When it is ultimately removed as part of building demolition or renovations, steel used in metal roofing is fully recyclable, allowing it to credibly claim both a high level of recycled content and 100 percent recyclability by recognized definitions. The product’s recyclability also provides significant savings on construction removal and disposal costs.

Residential buildings can also benefit from steel roofing applications. This sector has grown significantly as residential customers begin to see the long-term energy savings and other benefits of steel roofing. For residential customers interested in steel roofing, a rebate coupon for up to $500 is available from Canadian Sheet Steel Building Institute (CSSBI).*

* Visit steelroofsource.com.