The building envelope, referring to the outer shell of a building separating the interior and exterior, serves as a barrier against heat, cold, moisture, noise, and air infiltration. The components of the building envelope, including insulation, windows, walls, doors, and roof, play a critical role in the overall energy efficiency and performance of the structure.
Substantial evidence supports the importance of the building envelope on overall energy efficiency. Several studies identified saving potentials from the building envelope in European countries in the range between 75% and 80%. Another study noting that about half of the annual air conditioning heating energy consumption of public buildings were consumed by the heat transfer of building envelope.
Traditionally it has been difficult to evaluate the actual thermal performance of the building envelope. Pressurizing the building and conducting a blower door test may be impractical and cumbersome. Handheld thermography usually does not provide detailed insights or recommendations. These challenges may have contributed to the building envelope being overlooked in the past.
A logical first step to understanding the actual thermal performance of the building envelope is undergoing a comprehensive audit. Modern technologies have evolved where these audits can be done with a high degree of precision while being convenient, timely, and cost-effective. The audit should be able to get into granular details and identify specific issues throughout the building envelope such as moisture accumulation, thermal bridging, poorly performing windows, and areas of poor or degraded insulation to name a few. Ideally, you would know which windows, walls, doors, roof, etc. are performing poorly from an energy leakage point of view and empower you to take specific and targeted repairs or retrofits that maximize the financial investment.
Having a detailed understanding of the building envelope is the first step in planning and executing on building envelope retrofits and repairs that will save energy use and associated dollars. Retrofits are crucial to realizing the energy savings potential of the envelope because nearly 85% of residential and 55% of commercial buildings that exist today will still exist in 2050 . In order to meet our net zero targets, Canada needs to retrofit one building per minute . However, at the current rate of retrofits of under 1%, Canada would need 142 years to retrofit all homes and 71 years to retrofit all commercial and public buildings .
The building envelope is a critical line of defense against energy loss and environmental elements, making it an essential aspect of any decarbonization plan. As existing building stocks age, the building envelope will play an even greater role in sustainability and energy efficiency in the built environment. Whether the focus is on financial savings or net zero goals or both, it is critical to have an accurate diagnosis of the building envelope in order to begin planning retrofits that will maximize energy savings and return on investment.
 M. Hummel, R. Büchele, A. Müller, E. Aichinger, J. Steinbach, L. Kranzl, A. Toleikyt, S. Forthuber. The costs and potentials for heat savings in buildings: Refurbishment costs and heat saving cost curves for 6 countries in Europe. Energy and Buildings, Vol. 231, 15 January 2021, 110454. https://www.osti.gov/servlets/purl/1651335
 Analysis of the building envelope influence to building energy consumption in the cold regions. Guohui Feng a, Shuai Shaa, Xiaolong Xua. Procedia Engineering 146 ( 2016 ) 244 – 250.
 Harris, Chioke. Opaque Envelopes: Pathway to Building Energy Efficiency and Demand Flexibility: Key to a Low-Carbon, Sustainable Future. United States: N. p., 2021. Web. doi:10.2172/1821413.
 National Research Council presentation on Platform to Decarbonise the Construction Sector at Scale, 2022.
 National Research Council Canada Green Building Strategy, 2023.