Mass systems like roofs should not need to be replaced prematurely. They should be properly designed to be durable. If a building is designed to last for the long-term with minimal maintenance and ease of replacement when it comes to the end of its service life, then it is truly sustainable.
The life cycle of a roof is often benchmarked at 20 years; however, this is fairly short sighted as buildings are typically designed to last 50 years or longer. Although a 50-year roof would be great, it most likely wouldn’t provide the cost-benefit of two roofs that are properly designed to last 25 years each, meaning one roof replacement in the cycle of the building.
A roof that lasts longer is usually more sustainable since less waste is generated through the removal of an additional roof. Less energy is spent making that extra roofing product, transporting it to site and installing it. In this scenario, there is also the potential over the long-term for the overall maintenance and renewal costs to be lower, meaning that a durable, well designed roof may cost less as well.
To obtain the long-term performance of a roofing system, a proper design is required. Many minor changes can be made during original construction that can significantly impact the cost of the eventual system replacement.
When it comes to determining a suitable roofing assembly there are many factors to consider, including roof slope, type and frequency of penetrations, drainage, building location and orientation.
Every component of a roof system from the type of deck and insulation to the air barrier and perimeter flashings needs to be properly selected based on all the other variables because every component within the roof assembly is linked. For example, increasing the insulation can provide benefits to energy consumption. But if this is looked at in isolation, it can also cause problems with dew points within the assembly, leading to premature failure.
If building owners want to be sustainable, then they are really talking about a durable roof. The best way to provide a durable roof is to hire a professional roof consultant to properly design and oversee the roof installation. This will provide the best performance and can reduce maintenance and renewal costs over the long-term.
Josh Jensen is an associate and manager of the roofing division at JRS Engineering, a building envelope and roofing firm providing service in Western Canada and the Northwestern U.S.