Four Myths About Net-Zero Homes
3/16/2017
Imagine living in a home with practically no energy bills, where all your energy is produced on-site. A net-zero building uses a renewable energy system to generate as much energy as it consumes annually.
Most net-zero homes feature an ultra-energy-efficient envelope with generous amounts of insulation, meticulous air sealing, and a mechanical ventilation system. Many net-zero homes are built to the Passive House standard, a rigorous international standard for energy efficiency that is growing in popularity. There are many myths and misunderstandings about net-zero homes, so let’s explore a few of them.
Myth 1: You Might Run Out of Energy
Most net-zero homes are connected to the power grid and then have a solar energy system to generate electricity. When the system produces more energy than the home is consuming, the excess is fed to the power grid, and the homeowners are compensated for the energy. At night or on cloudy days, the home draws power from the grid. Homes that aren’t connected to the power grid typically rely on batteries for energy storage, and it is possible they could run out of power.
Myth 2: High-Performance Homes Have Poor Indoor Air Quality
Although this is largely a myth today, many older high-performance homes without mechanical ventilation did have indoor air quality issues. When building to the Passive House standard, heat recovery ventilation or energy recovery ventilation is necessary to ensure high indoor air quality.
Zehnder heat recovery and energy recovery ventilators are certified Passive House components that are up to 92 percent efficient in transferring heat from the exhaust air to the intake air, saving energy. These systems continuously extract stale, moist, or contaminated air from the bathrooms and kitchen and supply fresh, filtered air to the living spaces.
Myth 3: You Need a Large Lot in the Suburbs or a Rural Area
It is helpful for ultra-energy-efficient homes in North America to have a southern orientation to absorb solar energy in the colder months. On an ideal site, the sun’s rays would be unobstructed, but this is not necessary. There are numerous examples of homes built to the Passive House standard on small lots in urban areas.
When one is considering solar system output, less shading does result in greater energy production. In some cases, trimming trees or installing a solar system with microinverters or power optimizers boosts solar electricity generation.
Myth 4: These Homes Aren’t Worth the Upfront Cost
Net-zero homes almost always have a higher upfront cost. Although constructing an ultra-energy-efficient house involves little or no additional cost, a renewable energy system does increase costs (unless the solar system is leased instead of owned).
The return on investment of the solar energy system varies depending on the local cost of electricity, the cost of the solar system, and the amount of energy produced by the system. Where the cost of power is high, the solar system can pay for itself in a decade or less.
As net-zero homes grow in popularity, greater options exist for consumers. There are now more builders and architects trained in ultra-energy efficient building techniques and a variety high-performance building products provide more options than ever before.