Is “building envelope” one of those terms you didn’t know you didn’t know? "Building envelope" refers to the entire exterior of a building. It includes the roof, foundation, exterior doors, windows, sub-floor, insulation and exterior walls. Think of it as the wrapper that protects everything inside a building.

The building envelope is key to energy efficiency because it helps control the indoor climate: temperature, humidity, and air tightness. A tight building envelope allows for very few air leaks, making it easy to control the indoor environment. It is snug and free of drafts so your heating system doesn’t have to work harder than necessary to keep you comfortable. That means keeping the cold out and heat in during winter, and doing the reverse in summer.

A good building envelope is well ventilated with fresh air and prevents unwanted moisture from entering the building. The envelope works with other “systems” in a building (like ventilation and heating) to keep the building comfortable, energy efficient and healthy.

Maintaining this balance – few air leaks, breathability, moisture control, are what make the building envelope fundamental to the energy efficiency of a building. The balance is most challenging to control where the roof meets the walls and where the floor meets the foundation.

A loose or leaky building envelope can be the source of all sorts of problems. Heat loss means higher energy costs and unwanted moisture can cause mold, mildew, and even structural damage.

Not all building envelopes are created equal

The more efficient your building envelope the less energy it will take to control the indoor temperature and humidity.

It’s easy to improve the efficiency of a conventional building envelope (built to the current National Building Code). Choosing ENERGY STAR® certified windows and doors, and adding extra insulation (higher R-value), in more places, will make your building significantly more efficient. (According to ENERGY STAR®, certified windows can lower energy bills by an average of 12 percent.)

For a net zero home, the building envelope has all that and more. The building envelope of a net-zero home often begins with rigid foam insulation under the foundation. The building envelope often uses advanced framing, a technique that improves energy efficiency by replacing some timber with insulation. In many cases the building envelope is even wrapped in a layer of continuous insulation under the siding to improve comfort and lower energy use.

How to improve the building envelope of an existing building

Creating an efficient building envelope is simplest with a new build but it is possible to retrofit the envelope of an existing building to make it more efficient. Air sealing, adding extra insulation, and installing efficient doors and windows will all contribute to a more efficient building envelope.

  • Air sealing is the process of plugging any leaks in your home that allow cold air to enter and warm air to escape. Air sealing is done with caulking, weatherstripping, gaskets, foam, and tape.
  • Adding extra insulation to attics and walls will make a building more energy efficient. As well, upgrading to high-efficiency windows and doors, such as those that are ENERGY STAR® certified, will increase the efficiency of the building envelope.

The better the building envelope, the more comfortable, energy efficient and healthy the building will be; these are all important reasons to invest in this part of your building.

There are incentives available to upgrade your building envelope, for new builds and existing structures. Contact us today to learn how you might qualify.


What is included in the building envelope?

The building envelope refers to the entire exterior of your building. It includes the roof, foundation, exterior doors, windows, sub-floor, insulation and exterior walls.

What is R-value and why does it matter?

R-value is a measure of heat transfer through insulation materials. The higher the R-value the slower the heat transfer so the better the insulation is at keeping heat inside the home. Higher R-value insulation is typically more expensive but will help to reduce your overall heating and cooling costs.