Posted: July 31, 2017
Taking into consideration a respective regions environment and climate is critical to the long term performance of a building. Most of us would never wear a snow suit in Hawaii or shorts and a t-shirt in the middle of winter in Calgary. Like dressing for the weather, buildings must be designed to properly suit the climate in which they are built in. Tropical climates such as Hawaii have higher temperatures, more rainfall, and much higher relative humidity levels compared to a climate like Calgary where you can expect dry conditions with low relative humidity and temperature swings from -40°C to 35°C annually. A city like Calgary is a particularly harsh environment for building envelope design as the region experiences more than 120 freeze/thaw cycles throughout a calendar year. This is particularly challenging on the materials that are used in buildings as they must be able to withstand the stresses (i.e. expansion and contraction, flexibility, etc.) placed on the building as a result of drastic temperature swings. In addition to selecting the proper building systems and materials, there are several considerations that should be taken into account when designing a new building or assessing an existing building including energy efficiency and sustainability, technology, and comfort for tenants and building owners.
The National Energy Code of Canada for Buildings (NECB) is a National Model Construction Code developed by the Canadian Commission on Building and Fire Codes and published by the National Research Council of Canada to improve energy efficiency of Canadian buildings and reduce greenhouse gas emissions. The NECB sets a minimum standard for energy use efficiency within building systems. It covers elements of the building envelope, mechanical, and electrical systems, ensuring that buildings are efficiently designed and provide energy savings to owners and users.
A number of changes have come into place as a result of NECB. Where in previous building codes, the insulating value (R-value) of the insulation material (i.e. batt) itself in a wall was used, it is now required that the effective R-value of any wall including all thermal bridges such as studs, balconies, and other larger penetrations through the building envelope, be calculated for all building envelope assemblies. Under the prescriptive pathway of the NECB the effective R-value required in the Calgary Climate Zone for walls is R-27 and the effective R-value for roofs is R-35. Previous code requirements for walls were nominal R-12 under Part 9 of the building code. This is resulting in significant changes in the way in which the building envelope is designed. Insulation is more commonly being moved from within the stud cavity, to outside of the building to reduce the thermal effect of studs on the wall; however, this is also increasing the size of our buildings footprint.
Similarly, as there is a growing push to design more air-tight, highly insulated buildings in combination with mechanical systems that are forcing air throughout the building, we are creating a “pop bottle” effect. A small hole in the building envelope can lead to a number of large issues which is why the building envelope detailing of the air barrier, vapour retarder and thermal barrier have become more critical to define.
Innovative Building Materials & Technology
Building materials are evolving at a rapid rate. There has been an increase in the number of products coming into the market place to provide added insulation value, better air seals and vapour retarders, and are easier to install, saving time during construction. It is very important to understand the properties of these materials as-well-as their limitations. Early in the design process products need to be reviewed for suitability to the installed environment, applicability to expected and volatile weather conditions during construction and installation, as-well-as compatibility with other materials in the building and the desired long-term performance of the building.
The colder conditions expected in the northern region of Canada can result in higher energy demands as well as condensation issues as warm interior air meets the cold exterior air. Even the smallest openings of leaking air can lead to extensive frost and icicles. Specialized blower door equipment is utilized to measure air leakage coming from a building which helps identify construction details that require repair.
In building condition assessments, specific equipment is used such as thermographic cameras and borescopes to literally see into the walls and other building envelope assemblies. A preliminary review of a building envelope issue can be completed using the aforementioned tools. In addition, these same diagnostic tools can be used prior to completing high-cost removals and remedial repairs. For a recent condition assessment of a recreation centre, our team was able to confirm that the humid pool environment was not properly contained within the building, resulting in damages within the building envelope. This allowed the owner to understand the existing issues without invasive demolition.
A Role to Play in Comfort
Not only does the building envelope need to be properly designed for the exterior environment, but also the interior environment. This is where Building Science plays into building design. As our mechanical and electrical systems evolve as a result of smart home technologies being introduced in both residential and commercial properties, interior living conditions can be adjusted to anyone’s comfort. It is important for occupants to understand the impact that they can have and the role that they can play when it comes to maintaining the building envelope while achieving a healthy and comfortable interior living environment. Although experiencing higher-levels of heat and humidity during a vacation in Hawaii is perhaps a welcomed change, maintaining a building at higher than normal humidity levels in a location like Calgary, especially in the cold, dry winter, can lead to large issues such as condensation, lack of air flow, and deterioration of both interior and exterior building materials.
No matter what climate you are constructing in, it is important to consider all aspects of a building. Selecting the proper building systems and components for a respective climate can be a complicated process. As engineering consultants, we are well positioned to address any areas of concern that building owners may have regarding this topic. Our experienced team of building science professionals can help with the selection of proper building systems and materials at the beginning of the design stage for new builds as-well-as assess and review existing buildings and how their respective systems and materials are currently performing and how those same materials may impact the exterior and interior of the building envelope in the future.