Net zero homes: what the label means and how to build one
A net zero home in Canada produces as much energy on site over a year as it uses, usually with a very efficient shell, a heat pump and rooftop solar panels. A net zero ready home has the efficient shell and the rest of the design but stops short of installing the panels.
What does net zero home mean?
The idea is an annual balance. Over twelve months, the energy the house generates matches the energy it draws. On a given winter night the house still pulls power from the grid, and on a sunny July afternoon it pushes surplus back. The balance only works across the year.
Definitions differ between programmes, and some count only the energy used for heating, cooling, hot water and ventilation, while others include appliances and lighting. Before comparing two houses, check which loads each label includes.
What is the difference between net zero and net zero ready?
A net zero ready house is designed and built so that adding solar panels later would be enough to reach net zero. It has the insulation, airtightness, ventilation, efficient equipment and structural and electrical provisions for the array, but no panels. Many builders offer it because the panels are the part that can be added at any time and that price changes the most from year to year.
A net zero house includes the generation, and its performance is normally confirmed by a licensed energy advisor using modelling and testing. The difference matters when you read a listing, since the two phrases are easily confused.
What are the steps to a net zero home?
- Reduce the load first. Cut heat loss with continuous insulation, good windows and a tested airtight shell. A sensible insulation order applies to a new design as much as to a retrofit.
- Use the sun in the design. Orientation and glazing choices lower heating needs for free; see passive solar design.
- Choose efficient equipment. Heat pumps for space heating and often for hot water move heat instead of making it. The cold climate heat pump guide covers what to check.
- Size generation last. Solar panels are sized from the remaining annual use, as described in the guide to how many panels you need.
The order matters. Panels bought to cover a leaky house cost more than insulation that removes the need for those panels.
Which mistakes cost the most on the way to net zero?
Three show up repeatedly. The first is oversizing the solar array to compensate for a weak shell, which spends more than the insulation would have. The second is ignoring the electrical side: a heat pump, an electric vehicle charger and an induction range together can need a panel upgrade, so the service size should be planned early. The third is judging the result from one summer. Net zero is an annual figure, and the first full year of utility data is the honest test of whether the model was right.
A worked example of the annual balance
Suppose a house is modelled to use 9,000 kWh of electricity a year after a heat pump replaces gas heating. A panel array that produces roughly 1,100 kWh per installed kilowatt in a sunny prairie location would need around 8 kW to match that. Those are assumptions for illustration only, because output depends on location, tilt, shading and the year's weather, and a quote or a modelling report would replace them.
The same house with a better shell that needed only 6,000 kWh would need roughly 5.5 kW. The shell upgrade, not the array, did most of the work.
Where does Drake Landing fit in?
Drake Landing Solar Community took a different route to a low-carbon house: shared solar heat and seasonal storage for 52 R-2000 homes, with 800 flat-plate collectors on garage roofs and 144 boreholes about 35 m deep. It reached 100 percent solar space heating in the 2015-16 season but did not generate electricity, so it was not a net zero electricity design. The lesson that carries over is the order of work, since the efficient homes were what allowed such a modest heat supply to be enough. Read the full how it works page for the system.
Quick answers
What is the difference between net zero and net zero ready?
A net zero ready home has the efficient shell and equipment to reach net zero, but without the solar panels. A net zero home includes the generation and balances its energy over a year.
Do net zero homes use no energy from the grid?
No. They draw from the grid when generation is low, such as winter nights, and export when generation is high. The balance is measured across a full year.
Is a net zero home more expensive to build?
Typically yes, because of better windows, more insulation, airtightness work and the solar array. How much more varies by region, design and year, so builder quotes are the only reliable guide.