Mention the term “Net Zero” and most people think of solar panels mounted on a roof. It’s generally assumed that homeowners with solar panels are trying to reduce their hydro bill and/or their impact on the environment.
By definition, Net Zero Buildings (ZEB) have net zero energy consumption. They are designed, modelled and constructed to produce as much energy as they consume over a year. These buildings will at times consume non-renewable energy and produce greenhouse gas (GHG) emissions but will offset that by reducing energy consumption and greenhouse gas production the rest of the year by the same amount. A significant reduction in energy costs, regional rebates and tax incentives combine to make zero-energy buildings financially viable and a sound investment.
Whether new or renovated, net zero homes are up to 80% more energy efficient than traditional new homes. They use renewable energy systems to produce the remaining energy they need. By choosing net zero, your utility bills will drop to an all-time low, and they’ll remain low all year.
Net zero homes deliver exceptional comfort all year round. They offer superior draft-free heating and cooling, thanks to a sealed building envelope, super-insulation and high-efficiency windows and doors. A filtered fresh air system significantly reduces dust, pollen and outdoor air pollution, for exceptional indoor air quality. Outside noise is virtually silenced.
The development of a zero-energy building is typically motivated at least partially by a desire to have less of an impact on the environment. According to the US Department of Energy, traditional code-compliant buildings consume 40% of the total fossil fuel energy in North America and the European Union. Residential buildings are significant contributors to greenhouse gases.
To combat runaway energy consumption, energy codes are being introduced and gradually implemented for new construction across North America and Europe, based upon the carbon neutrality principle. Buying a net zero home or retrofitting means you’re doing your part to reduce your family’s carbon footprint while helping to preserve natural resources for future generations.
Net zero isn’t just for new construction projects. If you love the neighbourhood you live in and your home, your building might be a candidate for a net zero retrofit. PACE (Property Assessed Clean Energy) is a financing tool for homeowners interested in investing in a deep energy retrofit.
Canada’s commitment to net zero
In March of 2022, the National Research Council published the latest version of the 2020 National Model Building Codes for new buildings. The latest version of the codes is an integral component of Canada’s climate action plan. The National Building Code (NBC) pertains to low-rise buildings.
The latest version of the model codes presents a 5-tier performance system. Step 1 represents the minimum building code. Step 2 is 10% more efficient, Step 3 is 20% more efficient and Step 4 is 40% more efficient than the minimum code. Step 5 in the model codes targets a “Net Zero Energy Ready” standard for the year 2030 and net-zero emissions by 2050. Net Zero Energy Ready means that with the addition of a renewable energy source the building is so energy efficient it can easily supply its own needs.
During the 2021 federal election, the Liberal Party promised to “accelerate” the rollout to 2025 adoption, while adding emissions to the code. Provinces, cities and municipalities across Canada have set ambitious climate targets. So far, only the Province of British Columbia has committed to a Net Zero Energy Ready and Zero Carbon code, while revising the target date to 2032.
The BC Energy Step Code is the latest development for energy efficiency in British Columbia. It sets energy-efficiency targets for new homes; a 5-tier program with 5 steps that will form part of the BC Building Code between now and 2032.
Net zero: energy
Reducing energy consumption
An energy model is used during the design process to optimize the home’s specifications, then confirm that your new house or energy retrofit will achieve Net Zero Energy or Near Net Zero Energy at completion. Your home’s building envelope separates the inside of your home from the outside, protecting its interior while facilitating climate control.
Here are some of the design considerations during the net zero design process:
- an airtight building envelope
- super-insulation with R-values from R-42 to R-56
- elimination of thermal bridging with double-stud framing
- air-tight triple-glazed, Low-E (low-emissivity), inert gas-filled windows (0.20 U-value Btu/hr-ft2-°F or better)
- a solar shading strategy that allows the sun to heat the building when needed and reject heat to avoid overheating
- air-tight thick doors with multiple gaskets ( U-value of 0.14 Btu/hr-ft2-°F or better)
- Expanded polystyrene (EPS) under the concrete floor, Insulated Concrete Form (ICF) foundations and perhaps an additional interior layer of expanded polystyrene or a framed wall with batt insulation
- a geothermal or ground source heat pump (GSHP) system (running at approx. 250% efficiency); or alternately an air-source heat pump or electric baseboard heating
- a heat recovery ventilation (HRV) system to capture heat and exchange stale indoor air with fresh outdoor air
Passive solar energy
Where possible, placing 50% to 60% of the window surface area facing south allows energy from the sun to be absorbed by the thermal mass of the concrete floor and pillars. The building’s thermal mass gathers and stores heat energy during the daytime, releasing it during the cooler nighttime hours.
Solar-electric systems use photovoltaic (PV) modules to generate as much electricity as the home consumes over a year. The solar arrays are usually tied to the power grid. A grid-tied system means that your home will provide surplus energy to the grid during the day, then draw energy from the electrical grid during the evenings, or when the home needs more power than the solar arrays are generating at the time.
Another option is storing excess energy in a battery backup system. Batteries can provide backup power in the event of a power outage, or offer the opportunity to disconnect from the power grid, saving line service charges from the power utility company.
Net zero: water
In a net zero water building, the alternate water used and water returned to the original source equal the building’s total water consumption. A net zero water building is designed, constructed or retrofitted to minimize the total water consumption, maximize alternative water sources, minimize wastewater discharge and return water to its original source.
Your building’s total annual water use is calculated by adding all the freshwater use and alternative water use. Next, you add up the alternative water use, treated wastewater and stormwater returned to its original source. If the sum of the water returned is equal to or greater than the total annual water use, your building is considered net zero water.
Rainwater collection, harvesting or rainwater catchment is the collecting of run-off from your building to store it for later use. Rainwater is a relatively clean and free source of water. Rainwater can be added to your home’s grey-water system, promoting self-sufficiency, while helping to conserve water.
Net zero: waste
Canadian energy, water, and waste management have typically focused on reducing consumption first, then encouraging alternative paths to reduce resource use, impact, and costs. The ultimate target is zero waste, completely diverting waste from the landfill during the construction phase.
Net zero waste buildings have not yet gained the public and government attention of net zero energy buildings, but municipal authorities and stakeholders in the construction sector are beginning to work toward zeroing waste. The policies and tools adopted by the building construction industry currently work on the principles of the 3Rs – reduce, reuse and recycle – while striving to minimize waste in landfills and incinerators for ecological and economic gain.
Once operational, all buildings should generate their own energy on-site and also adhere to strict consumption limits. Garbage, spent containers and consumer products, and food scraps must be recycled to the extent possible. Greywater from the building’s sinks and showers can be reclaimed. Human waste also needs to be addressed, so all wastewater is infiltrated or reused on-site, and sewage sent for municipal processing is kept to a minimum. Some net zero waste homes separate the three wastewater streams into black, grey, and stormwater, managing each individually.
Natural sustainable landscaping
Native plants are essential to creating sustainable landscapes. Native plants are those that existed in your geographic region before Europeans settled in North America. In modern suburban neighbourhoods, healthy native habitats have been replaced by vast expanses of lawns, with only a few trees and other plants added as accents.
These manicured yards are dependent on irrigation, fertilizer, chemicals, and gasoline-powered mowers and trimmers for maintenance. This is not a sustainable practice. The constant use of fertilizers and pesticides produces sterile soil, devoid of the microbes your plants rely on for survival.
Successful sustainable landscapes incorporate plants that are native to the region into the design. By understanding the endemic plants in your community, select varieties can be reintroduced to restore the existing local biodiversity, while considering their harmony with the immediate surrounding landscape. Care is given to choosing those that won’t seed excessively or spread vegetatively, invading surrounding gardens and natural areas.
Your garden spaces can be more efficient at capturing rainwater and preventing runoff. Plants that have root forms which hold soil help prevent erosion. Native plants are pre-adapted to grow in your area with almost no input of water or energy. They are part of the local food web, providing nectar for insects, shelter for birds, and food for local wildlife. When you choose natural sustainable landscaping you’re participating in the conservation of flora and fauna in your region.
Mounting solar panels on the roof and making your home more energy efficient is not the ultimate destination. Net zero energy is the first milestone in each household’s net zero journey towards sustainable living in the twenty-first century.