The many faces of zero

December 15, 2020

Zero seems a simple enough concept. Nothing. Zilch. Nada. But there's more to zero than meets the eye, and it means different things to different people.

Last week Mike Darmon, local cycling advocate and a member of our Board of Directors, sent me a Royal Lepage listing for a property billing itself as a "Beautiful Cape Cod NET ZERO Home". Here's more about this house from the ad:

Imagine having your power bill paid for every month. A 40 panel solar array is included and brings in $3461 annually (averaged over the past 5 years) with the annual total electricity bill last year at $3278. That’s NET ZERO.

The first thing that struck me about this ad was that we've come a long way from when I worked in the solar business eight years ago. Back then, realtors were very nervous about solar panels. Yes, solar provided the homeowner with revenue under the now-closed MicroFIT program. However, realtors feared such a component - they hesitated to call it a feature - was poorly understood by the buying public, making the house a tough sell.

A breakthrough came after someone, possibly me, pointed out that it was like having a built-in rental unit with a tenant that never made a peep, occupied no square footage, and always came through with the rent. Back in those days, a solar array yielded as much as $10K per year (noting that it would have cost over $80K to install). Realtors and buyers eventually came around.

Fast forward to 2020. The term "net zero" is increasingly in vogue. It's used in policy discussions at the international and federal level. It's central to the goal that guides our work - making Guelph net zero carbon by 2050.  Award-winning local homebuilders like Terra View and Claxton + Marsh (formerly Timberworx) proudly attach the label to their developments. But does Terra View mean the same thing when they say "net zero" as the Royal Lepage listing and our community-wide goal?

Not quite. It all depends on whether you look at money, energy, or carbon.

First, the listing. It compares solar array revenues with the utility bill costs, finds them about equal, and claims net zero. The house makes as much money as it costs to run it. So yes, this home is net zero - in dollars.

However, I'd guess the solar array produces about 12,000 kilowatt-hours (kWh) per year. Between its electric baseboard heaters and (I expect) electric water heater, it uses around 15,000 kWh per year, or 25% more energy than it produces - not net zero energy. Also, while the solar array doesn't emit any carbon dioxide, the Ontario electricity system does - not much, since it relies on non-emitting nuclear and hydroelectric sources, but not zero. All told, this house emits about 100 kilos of CO2 per year. That's not zero carbon, but it's pretty darned good. Plant a tree each year, and you've pretty much offset your house's emissions.

What about Guelph's net zero home builders?

Rooftop solar now uses an approach called net metering. You use what you make; if you make extra, you get a credit; if you under-produce, you can draw on your accumulated credit; and at the end of the year, it all balances out (except for unavoidable grid connection costs, which amount to about $600 per year). A well-designed rooftop solar array will produce as much as the building uses. Because the energy you send to the grid has the same price as the energy you take from the grid, it's a wash whether you're looking at dollars or kilowatt-hours.

Here's the rub: The atmosphere doesn't care about net zero dollars, or even net zero kilowatt-hours. If you're worried about the future of the planet, net zero carbon is where you want to be. A house is only net zero carbon if it doesn't use any natural gas. Natural gas emits six times more carbon dioxide than the equivalent energy coming from the Ontario grid. To offset a natural gas furnace with solar panels would require several rooftops' worth. Not happening. As long as you use a natural gas furnace, water heater, or both, you can forget about becoming net zero carbon. 

Fortunately, Terra View and Claxton + Marsh homes don't use natural gas for heating. Instead, they use a heat pump, which uses electricity way (three times) more efficiently than the baseboard heaters in the Cape Cod house. That means these builders achieve the trifecta - net zero dollars, net zero kilowatt hours, and net zero carbon. They’re way ahead of where the market will inevitably go: the Canadian Building Code is destined to be net zero by 2030.

There’s one more part of the story, though. Regardless of how much carbon dioxide a house emits as it operates, the building itself has a carbon footprint. Manufacturing the building materials, getting them to the site, and putting them all together results in a potentially huge amount of so-called embodied carbon. The worst-offender materials are concrete, steel, and glass fibre insulation. Put all that together, and you end up with a hefty carbon footprint before you even move in.

However, this glum picture can be turned not just neutral, but into a good-news story. There are alternative - mainly plant-based - building materials that not only have a low-emissions manufacturing process, and aren't significantly more expensive, but that actually store carbon that would otherwise be in the atmosphere, warming the planet. So instead of a carbon debt, you can start your new homeownership experience in a carbon-positive position.

As an added bonus, those alternative materials offer an economic opportunity. Pulp and paper mill towns across the country have been hit hard by the combined effects of foreign competition, increased use of recycled fibre, and declining demand as newspapers move online. A renewed market for wood fibre-based products could breathe life back into some of these small towns.

The Canadian Home Builders’ Association Net Zero Energy Council is helping to spread the word, as are organizations like the Endeavour Centre. Builders like Terra View and Claxton + Marsh, by educating customers about their carbon footprint and providing a solution for them, are clearing the way for a fulsome conversation about the complete carbon picture. All of this will contribute toward our Pathway to Net Zero Carbon goal that all new home construction will be net zero carbon by 2030.

Let’s all zero in on that.