The Importance of the Building Envelope

The Importance of the Building Envelope

Understanding Air Flow, Air Sealing and the Building Envelope | Image via U.S. EPA

What is the Building Envelope?

A building envelope is the physical separator between the conditioned and the unconditioned environment of a building. Due to its role in the maintenance and protection of a structure it is one of the most important components in building design. The envelope includes many components of a building: walls, floors, roof, windows, doors and quality construction can enhance the architectural design whilst improving the thermal performance of a building.

The envelope determines the formal qualities of the building and is a crucial part of the architectural design. A good building envelope involves using exterior wall designs and materials that are aesthetically pleasing, structurally sound, and climate-appropriate. The 3 basic elements of a building envelope are air and thermal barriers and weather.

Air Barrier Systems

The external environment is very dynamic but of course, people want the internal environment to be constant. To create a good building with high comfort and low energy for its occupants, the design first relies on the envelope and second on the services.

One of the important parts of your building envelope is the air barrier system. The air barrier system prevents unwanted air flow and leakage from the interior of your home to the exterior. It also helps to:

  • Ensure a comfortable indoor environment
  • Prevent moisture condensation
  • Minimize soil gasses moving into the interior

Vapour Barrier Systems

Also the vapour barrier is equally important in your building envelope as the air barrier. It protects your home from unwanted moisture and water in your attic, walls, floors, and roof. The Ontario Building Code specifies the number of different types of vapour barriers: vapour barrier paints, foam plastic vapor barriers, and polyethylene and other membrane type vapour barriers.

In order to work efficiently a vapour barrier needs to be installed correctly or if not it may fail and cause damage. A vapour barrier needs to be: 

  • Installed close enough to the insulation in order to prevent condensation
  • Installed on the warm side of the floor, wall, or ceiling

Why is the Building Envelope Important?

One of the easiest ways to significantly increase the performance of a building is a good building envelope design. The overall construction is important in controlling the levels of ventilation, light and heat flow.


A way how we can measure the quality of a building envelope is whether it can allow for the ventilation of fresh air whilst protecting the structure from air leakage. If the envelope and fenestration components are not sealed correctly, natural weather conditions such as strong winds can increase the amount of air that escapes through the envelope. Therefore, it is possible to increase the energy efficiency of a building by restricting the passage of air.


With both new build projects and refurbishments, adding thermal insulation to a building envelope has proven to be a cost effective way to reduce energy bills. Insulation provides resistance to energy flow by reducing the amount of energy required to cool or heat a building throughout the year. Can also contribute to the reduction of energy consumption maximising sunlight in the design by incorporating glazing.


The arrangement of doors and windows can have a significant effect on building envelope efficiency. Well-sealed energy efficient windows and maximising sunlight with glass can be significant in design, but regulating the orientation and the size in a large commercial premise is essential to balance the flow of heat that is generated from natural light.

Home Insulation

One of the things you can do to affect the airtightness of your building is to ensure that you have installed adequate insulation. But what is adequate differs for each house, the building sciences approach means that each part of your building envelope and the varied advantages, needs, and disadvantages of each home must be considered as a whole instead of individual parts. One of the key terms in insulation is R-Value. Which refers to the material’s ability to withstand heat transfer. A higher R-Value doesn’t equate to better airtightness of your building and needs to be considered by your contractor in relation to the other component parts that are making up your building envelope.

When it comes to insulation we recommend paying attention to two places in the home: the attic and basement. The most important place in your home is the attic when it comes to making your building more airtight. If the attic is not insulated the conditioned air may be escaping into the attic and out through the roof ventilation or that heated attic air may be coming down and making for an uncomfortable environment. An uninsulated basement may have moisture problems that can lead to mold growth. Insulating a basement can help improve the efficiency of the entire home. Spray foam insulation adds structural stability as well as airtightness, making it an excellent all in one application.

Contact the Experts

When it comes to addressing the building envelope, you can trust the experts at Eco Spray Insulation to help you to get it right. As we have mentioned above, insulation plays a huge role in an effective building envelope. Our top choice is spray foam insulation for new builds and retrofits because it acts both as a vapour and air barrier in one. It also provides excellent R-Values and insulating power.

The team at Eco Spray with nearly a decade of experience working with insulation and The Ontario Building Code, have the practical knowledge and skills to make installation easy. Contact us at 1-416-860-6664, or by email at [email protected] and our Professional Team will be happy to assist you.

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