Building Envelopes, Energy Efficiency, and Your Home

Published on October 11, 2019

The building envelope is one of the most important pieces of your home, and one of the most important aspects in achieving overall home energy efficiency. The building envelope is what separates conditioned and unconditioned space. Therefore, if there are any holes or leaks in the building envelope, you are significantly reducing the overall energy efficiency of the structure.

The building envelope is also concerned with the technical performance of the home. Again, if there are any holes or leaks in the home, it will notably increase the need for your mechanical system to continuously run in order to keep your home comfortable. This results in reduced overall performance, reduced energy efficiency of the home, and increased utility bills.

What Is A Building Envelope?

A building envelope is what separates conditioned and unconditioned space in a home or building. Essentially, it is what protects you from the harsh elements -- rain, snow, wind, and sun.

The building envelope is made up of multiple layers of barriers: air barrier, vapour barrier, thermal barrier, weather barrier, and interior/exterior finishes. All of these layers work together harmoniously. All barriers play unique roles as part of the building envelope. If one of the barriers is insufficient, it affects the other barriers. This, in turn, will reduce the energy efficiency of the home. The continuous layers make up the barrier that helps to keep your home warm and dry.

Air sealing, including caulking and weather stripping, are a cost effective way to reduce the amount of air leakage in your home. The blower door test, or air tightness test, completed during your home energy audit will indicate where the air leaks are, and how much your home is leaking. However, air sealing alone does not eliminate the need for proper insulation. Proper insulation is also key to an airtight, energy efficient home. If you are looking to air seal, or increase the insulation in your home, don’t forget there could be rebates available! The Home Efficiency Rebate offers up to $5,000 for energy efficient upgrades made to your home. 

Why Is A Building Envelope Important?

The building envelope as a whole is extremely important to the home as it protects you from the outside elements. It also plays a major role in the overall energy efficiency of your home. If any of the barriers fail, your home will be much less energy efficient. For example, holes or leaks in the air barrier will allow outside air to mix with the conditioned air. This means your HVAC system will be working overtime to make your home comfortable.

Alternatively, if the thermal barrier isn’t at an optimal level, you’ll likely experience a home that is unevenly heated/cooled. Your home will experience a loss of energy through heat loss. The thermal barrier, or insulation, is a key component to a home’s overall energy efficiency. It plays a large role in keeping your home evenly heated, comfortable, and affordable.

All of the barriers that make up the building envelope play key roles in the overall energy efficiency of your home. If one isn’t working sufficiently, it affects the entire building envelope.

How Does A Building Envelope Affect Energy Efficiency?

If your home doesn’t have a complete, airtight envelope, you’re essentially paying to heat/cool the outside air. For the average home, the interior air is exchanged with outdoor air approximately 7 times every hour. That’s the equivalent of having a window open at all times.

If your home is airtight, you pay less money heating and cooling the air as it’s not constantly being exchanged with unconditioned, outdoor air. Furthermore, if the insulation values (the thermal barrier) are effective, you’re going to have a more comfortable home.

Since the building envelope is what protects you from the outdoor elements, it’s one of the most important components in overall home energy efficiency.

What Is A Hole In A Building Envelope?

A hole in a building envelope is where unconditioned air (or outside air) is allowed to penetrate the air barrier in the building envelope. This means that outside air is able to make its way through your home and into the interior to mix with the conditioned (or inside) air.

An airtight home allows for an easier controlled environment; easier to control temperature, moisture, and humidity. An airtight home also means that less conditioned air is escaping to the outside, so you’re not spending money by constantly having your HVAC running to keep your home comfortable.

A blower door test is the most effective tool to determine how airtight your home is. During a blower door test, a fan is placed in your main door frame and pulls the inside air to the outside of your home. The air is then drawn back in through leaks or cracks in the home. The blower door test measures how many times your home exchanges indoor air with unconditioned (outdoor) air. This is measured in air changes per hour, or ACH, and the lower the number, the better. 

How Do I Know How Energy Efficient My Building Envelope Is?

An energy assessment, or an energy audit, is the most effective way to determine if your building envelope is energy efficient or not. It’s also a great tool to help you decide which upgrades would be most beneficial to your home and your utility bills.

After your Registered Energy Advisor completes the walkthrough of your home during the energy audit, they will provide you with an EnerGuide label and a list of recommended upgrades. The EnerGuide label indicates how energy efficient your home is in the form of an EnerGuide rating in gigajoules per year. For more information on your EnerGuide rating, contact us today.

By having an energy audit conducted on your home, you could also be eligible for rebates. Having an energy audit performed on your home before any renovations have begun is the first qualification step for the Home Efficiency Rebate. This rebate initiative put on through Enbridge Energy Inc. allows Ontario homeowners to receive up to $5,000 in home energy upgrade rebates.

Contact BSG today to schedule an energy assessment on your home. You can call the BSG offices at 1-866-333-3920, fill out a form on the contact us page, or speak to the BSG office through the live chat option on the BSG website. By having an energy assessment completed, you’re one step closer to a more energy efficient, comfortable, more affordable home.