Challenge 3: Home Envelope

Space heating makes up 63.6% of household energy use, and the air tightness of your home plays a vital role in its energy efficiency. In this challenge our families explored options to improve their home’s seal to increase energy efficiency and reduce related emissions.

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Keep warm air in, cold air out, and carbon emissions down

Canada is a heating dominant country. In the winter, energy is needed to heat your house. A home’s envelope – which consists of the structural building, insulation, windows, doors, and air sealing – can keep the heat in and the cold out. 

When there are areas that are drafty or uninsulated and doors are thin, heat can escape. Unfortunately, you may be heating the sky while you pay for your monthly energy bills and heating up the planet with unnecessary emissions!

Get the facts

Can stripping make you warmer?

Sealing gaps in doors and windows with weather stripping or foam tape will eliminate drafts and make your home feel warmer.

Intensité carbone de l’électricité, 2020 (grammes d’équivalent CO2 par kWh). Source : Régie de l’énergie du Canada
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Improve your home envelope to decrease emissions

Accordingly to the Canadian Home Builders’ Association (CHBA), in a typical 2300 sq ft house built 30 years ago (1982), 75% of its energy consumption can be from just heating the house. When natural gas is used to keep this house warm, most (if not all) of the greenhouse gas (GHG) emission is produced by this single action. 

Thus, the more energy efficient the building envelope of the house gets, the less energy it requires to keep the house warm. As a result, both the energy bill and carbon emissions are reduced. This is also the main reason why some of the high-performance home standards, such as CHBA’s Net Zero Homes, require the building envelope of all Net Zero rated homes to be at least 33% more energy efficient than a typical new home built today.

However, you don’t have to buy a brand-new home to have a more energy-efficient home. Retrofitting your current home reduces energy use which saves money and decreases your household carbon footprint. It also makes your home more comfortable, and ultimately, more valuable.

The household challenge

In the Home Envelope challenge, our families explored ways to improve their home’s envelope to help keep it warm in the winter and allow cooling and airflow in the summer. 

To start they performed an audit of their home’s envelope: Looking for gaps around doors and windows. Considering the age of their windows and exterior doors. Seeing how many panes their windows have. Checking the outlets and switch plates on exterior walls to ensure they are insulated. Inspecting the insulation in their attic and walls and considering insulating basement walls and floor if they aren’t already. 

Families arranged for a professional energy efficiency home evaluation which included a blower door test to establish the airtightness of their home.

They then determined which changes would have the biggest impact on reducing their household emissions for the budget they had to spend. This was also the perfect time to look into any municipal, provincial, and federal loan and incentive programs available to retrofit their homes.

See how they did…

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    Home envelope for your household

    Replacing your home heating system before sealing your home means potential energy savings could leak out through gaps, drafts, and poor insulation and diminish your reduction of home heating carbon emissions.


    • Weigh your options: Each type of insulation is assigned an R-Value based on how well a material can resist heat. Higher values provide better climate control and energy efficiency for your home, but also come with a higher price tag.
    • Not all insulation is created equal: The material the insulation is made from will affect R-values, but typically the order of lowest performance to highest performance by installation method on a per inch basis is: #4. Blown-in (or loose-fill) insulation; #3. Insulation blankets (batts and rolls); #2. Spray foam insulation; #1. Foam board insulation
    • Don’t be afraid to mix it up: A specific insulating scenario, like ease of accessibility, may dictate the method of installation. In others, these methods can be combined to boost the R-value and home’s energy efficiency, like placing foam board insulation over existing batt insulation between studs or blowing insulation in to fill spaces through small holes in the walls.
    • The more Rs the better: The higher the R-Value, the greater insulation performance, resulting in more savings on your utilities bill along with a decrease in related emissions, though there is eventually a diminishing return.
    • Insulate from the bottom to the top: Insufficient foundation insulation, poorly insulated walls, or under-insulated roof can all add up to significant heat loss, with basements accounting for up to 20% of a home’s total heat loss.

    Windows and skylights

    • Add layers: Window units are classified by the number of panes of glass used in their construction and are single-, double-, triple-, or even quadruple pane windows, with each extra pane adding space to insulate your house from outside temperatures and noise.
    • Fill up with gas: The space between window panes can be filled with air, or filled with an inert gas to provide an even higher energy efficiency – either Argon, Krypton, or Xenon.
    • Know their value: Windows are assigned an ER or Energy Rating based on their energy efficiency in the colder months of the year, taking into account heat loss for the window unit as a whole, and how much solar heat is allowed to penetrate the window glass into your home.

    A new door, or even just a proper seal around an existing door, can make your home less drafty and keep the bugs and weather outside where they belong.

    Exterior Doors

    • Materials matter: A solid wood exterior door will have an R-value of R-2 or R-3, whereas an insulated steel or fibreglass door will typically have an R-value of R-5 or R-6.
    • Glass lets cold pass: Although it may be nice to brighten up an entry with natural light, exterior doors with large glass panes have lower energy-efficiency ratings.
    • Don’t double-up: With the high efficiency of modern insulated doors, there is negligible benefit to adding an exterior storm door as second thermal barrier, and in some instances the heat from the sun that builds up in the space between the two doors can warp or damage an insulated door.

    If major retrofitting isn’t an option right now, there are many cost-effective DIY solutions that can increase the energy efficiency of your home by reducing drafts and heat loss. 

    Quick hits

    • Mind the gap: Check your weather stripping and replace it once it is damaged or too compressed to create a proper seal. Use foam tape to fill gaps in window seals.
    • Have a foam party: It’s easy to use spray foam insulation or caulking to fill gaps around windows, doors, and any other place cold air can sneak into your home such as where services or plumbing go through your exterior walls.
    • Wrap it up: If you’re not ready to replace your windows quite yet, applying heat shrink window film is cost-effective and can make a big difference in stopping drafts and provides an additional layer of air-filled insulation.

    Did you know?

    • Due to updates to building codes, houses built prior to 2010 may use at least 25% more space heating energy than those constructed after increased insulation and air tightness requirements.
    • Often there can be an insulation gap along the “sill” where a house sits on top of the foundation
    • Windows and doors can account for up to 25% of total heat loss in your home.
    • You can make a DIY leak detector using 2-3 sticks of incense. Light the incense and hold close to the place you want to check for leaks. Slower leaks will cause the smoke to trail away or towards the leak, while larger leaks will cause the smoke to dissipate and the tips of the incense to glow.
    • An insulated fibreglass or steel door, 3.81 cm (1-1/2 inch) thick, without a window offers more than five times the insulating value of a solid wood door of the same size.

    Contest Rules & Regulations

    Get yourself to zero

    To help your own household get closer to a zero-carbon lifestyle, see how our five families navigated unique journeys to net zero and learn from their shared their personal tips and tricks.