Building envelope

“Building envelope” is the technical term for a building enclosure. It includes all the materials that keep the people inside comfortable by stopping the outdoors from coming in.

While that sounds simple, it helps to have a better understanding of the individual components involved, especially if you’re considering making improvements. Making a building more airtight is an excellent way to cut energy use and costs, and doing so is often one of the first recommendations from an energy audit.

The less heating and cooling you need to use, the lower your energy costs will be. In that sense, building envelope upgrades correlate directly with energy cost reductions.

“When done correctly, the return on investment for a building envelope upgrade can be significant, both from a financial perspective and from a ‘soft benefit’ perspective—meaning health and well-being improvements for the people who use the building,” says Paul Reynolds of Affine Climate Solutions, a Vancouver, BC consultancy that specializes in decarbonization solutions and climate resilience.

What constitutes a building envelope?

While the pieces of a building envelope are what you might expect (foundation, walls, roof, windows and doors), there is more to it than meets the eye.

It helps to think of the walls and roof as “components,” says Reynolds—a term that reflects the fact that walls and roofs are more complex than they appear.

A wall component includes insulation, a vapour barrier, exterior cladding and an interior finish. A roof can consist of shingles, underlayment, insulation, a vapour barrier and, in some cases, attic ventilation.

“Both components include a range of elements that contribute to keeping the indoor environment separate from the outdoors,” says Reyolds.

What are the functions of a building envelope?

A building envelope contributes structural support and an aesthetic finish, says Reynolds. But beyond that, it also provides and influences:

• Weather protection—shielding the interior from rain, snow and sun
• Temperature control—helping the building’s heating and cooling systems maintain a comfortable temperature
• Moisture management—preventing water leaks and managing humidity levels so the air is neither too dry nor too moist
• A vapour barrier—preventing vapour from passing through the walls and ceilings to avoid damage from trapped moisture

These climate control aspects of the building envelope work together to offer advantages that many users don’t consider until something goes wrong.

For example, a sound building envelope lends resilience. “If there’s a power outage during a period of extreme heat or cold, and the building envelope performs well, the building will be able to maintain its target temperature for significantly longer than it would with a weak building envelope,” says Reynolds.

For businesses, an effective building envelope can motivate employees and customers to stay longer by improving indoor comfort, such as air quality, he adds.

“For example, if you’re in a location with air pollution, like during a wildfire, a good building envelope can prevent the smoke from coming in.”

It can also provide better acoustics—a sound barrier, in other words—which can be useful if the building is in a noisy urban location. Of course, it can also work the other way around, providing protection to those outside if the operations inside are loud.

How can I evaluate the quality of my building envelope?

An effective building envelope is important because it can help the building achieve and maintain the ideal indoor temperature using the least energy possible, says Reynolds. Heating and cooling systems don't have to consume as much energy if the air isn’t escaping through a weak envelope.

If you’re wondering if your building envelope is effective, you can get a general sense by making informal observations, says Reynolds. For example, perform a visual inspection of potential problem areas, such as under doors and around windows. “If you see daylight, you know there’s a gap in the envelope,” he says.

If you suspect a problem, you may be able to confirm it using a thermal scanner attached to your phone. You can buy a scanner for about $150.

“A decent scanner will show you any problem spots in the walls and roof that might not be as obvious as daylight coming in,” such as areas behind walls where insulation may be thin or absent.

Of course, the most formal and accurate way to measure the energy efficiency of your building envelope is to have an energy auditor conduct an assessment and provide recommendations on how to improve.

How can I improve my building envelope?

You’ve done some investigating or conducted an energy audit. You’re ready to start making improvement. You can start with something simple, like installing weather stripping around windows or door seals beneath doors.

With a bigger budget, you can also replace windows and doors with higher-performance ENERGY STAR-rated doors and windows.

Using materials that absorb and store heat (like concrete or brick) can help regulate indoor temperatures. These materials absorb heat during the day and release it at night, reducing temperature fluctuation

“You can also add to or improve your insulation,” says Reynolds. “However, that normally involves tearing out drywall, so it may be more labour-intensive and costly.”

If you can’t afford to take on that sort of larger project, Reynolds recommends waiting until you have another renovation and then applying a “climate lens” to the work. For example, if you’re opening a wall anyway, you may have an opportunity to improve the insulation.

“Consider what changes you can make to improve the building envelope and its overall energy efficiency,” says Reynolds. “There’s almost always a strong business case for building envelope improvements when you’re planning other renovations. It’s a minor capital increase for a significant improvement that will reduce operating costs going forward.”

Is there financial support to help me improve the efficiency of my building envelope?

Programs to help entrepreneurs retrofit buildings for greater energy efficiency vary across the country. BDC has put together a list of more than 60 provincial and federal active grants, tax credits and loan programs to support environmental initiatives.

Find out more from:

• Natural Resources Canada, which has a directory of ENERGY STAR rebates and incentives available in Canada as well as a directory of energy efficiency programs in Canada. It also has a Green Industrial Facilities and Manufacturing Program to provide financial assistance to businesses to implement energy efficiency solutions.
• The Canadian Climate Institute, which provides a searchable database of emissions reduction policies across Canada at the provincial, territorial and federal levels, including some that may offer financial incentives for businesses.

Next step

Learn how to retrofit your building to reduce its energy use.