During the cold, snowy winters in much of Canada, many of us rely on furnaces, boilers and baseboard heaters to keep our homes and offices comfortable — and hope they don't suddenly quit during a cold snap.

But what if you didn't need any heating equipment in your home? What if your community provided a greener, more efficient, more reliable source of heat using locally sourced energy? What if it didn't take up space in your home or office building, you didn't have to maintain it, and it was just about guaranteed to keep running and keep you warm through big storms and power outages?

That's the promise of district energy systems — along with climate benefits that have earned them an endorsement from the United Nations Environment Program. World leaders meet Dec. 2-13 for the COP 25 UN climate conference in Madrid to discuss next steps in implementing the Paris Agreement to reduce greenhouse gas emissions and curb global warming, and district energy is one potential tool.

The idea is that instead of having an individual heating and cooling system for each building, multiple buildings are hooked up to a single, central system — similar to the idea of hooking into a municipal water service instead of each building relying on individual wells. The heating and cooling is distributed to individual buildings through pipes that typically contain heated or chilled water.

It's not new — some district energy systems in Canada are more than 100 years old.

But thanks to environmental concerns and the desire in communities to use greener energy technologies for heating and cooling, new projects are popping up across the country.

"Yes, there's a real renaissance," says Bruce Ander, president and CEO of Markham District Energy in the Great Toronto Area. A past chair of the International District Energy Association, Ander has been working in the field for 40 years.

More than half of district energy facilities inventoried in Canada in 2014 had been commissioned since 2000, and more than half of them planned expansions in the near future.

They range from a project in Vancouver that recovers heat from sewer water to provide heat and hot water to more than 30 condo buildings to one that cools Toronto office towers in summer with water from the depths of Lake Ontario. And even smaller communities are jumping on board, including the village of Teslin, Yukon, which has installed a biomass system, and the rural municipality of Ritchot, Man., which has a district geothermal system.

Many new projects are underway such as:

Why? A major factor is climate change and climate change resilience.

In Canada, buildings are the third largest source of greenhouse gas emissions, after oil and gas and transportation, Environment and Climate Change Canada reports. And nearly two-thirds of energy use in buildings is for heating and cooling .

Vancouver's False Creek Neighourhood Utility used waste heat from sewage to provide heat and hot water to 30 condo buildings in the neighbourhood, which was redeveloped for the 2010 Olympics. (Darryl Dyck/Canadian Press)

Much of that comes from burning fossil fuels, either directly in furnaces or indirectly through power generation. In 2011, for example, natural gas was used to heat half of Canadian homes and electric baseboards were used to heat most of the rest , Statistics Canada reports.

When buildings are individually heated, there aren't many green options.

But Ander says, once a community has installed a district energy system, "Now you can unlock a bunch of technologies."

Buying local

Many energy sources used in district energy systems, such as biomass, sewage, lake water or seawater aren't very feasible or economically viable on a small scale.

The choice of energy source for a district heating system is what is available locally and can generate co-benefits for the local community.

For example, Vancouver captures the heat from families' hot showers, dishwasher and laundry loads in its high-density False Creek neighbourhood. The waste heat literally is heading down the drain, but can be extracted at the nearby sewage pumping plant.

"It's a great opportunity," says Alex Charpentier, acting manager of the False Creek Neighourhood Utility that runs the system. "In a dense urban environment, there's not many sources of local energy."

This is some of the distribution pipe used to carry hot water to buildings in the Charlottetown District Energy System. Such pipes are easier to install in areas that haven't yet been developed. (PEI Energy Systems/Enwave Energy Corp.)

Charlottetown has little land for landfills and no equipment installed to prevent methane generated by rotting garbage from escaping into the atmosphere, so it burns garbage in its district energy system, says Carlyle Coutinho, president and chief operating officer for the Canadian region at Enwave Energy Corp., which runs the system.

The heat is distributed through underground pipes carrying heated water.

Meanwhile, Teslin, Yukon, is surrounded by boreal forest. Installing district energy means it can now heat buildings with locally sourced wood chips, generating jobs and keeping $300,000 a year that would have been spent on imported diesel in the local community, said project manager Blair Hogan, president and CEO of Gunta Business Consulting.

The wood comes from trees cleared for development, and more will be cleared in the future to create fire breaks to protect the community from wildfires, a risk that grows with climate change.

"In every community, there's a unique technology for their unique situation," Hogan said.

In addition to accessing different heating and cooling sources, district energy systems make it easy to feed in new energy sources or switch altogether. For example, a system in St. Paul, Minn., switched from fossil fuels to biomass "almost overnight" without affecting customers, Ander said: "How it's fuelled doesn't really matter to them."

But it can have a huge impact on their greenhouse gas emissions.

'Key measure' for carbon targets

In fact, the United Nations Environment Program calls district energy a "key measure for cities/countries that aim to achieve 100 per cent renewable energy or carbon neutral targets." Its District Energy in Cities Initiative notes that district energy can:

Reduce energy consumption and costs from heating and cooling by up to 50 per cent.

Store large amounts of energy at low cost.

Make transitions to sustainable heating and cooling sources fast and cost-effective.

It adds that such systems are increasingly low-carbon and climate resilient — that is, they can often keep running through storms and extreme weather disasters that are becoming more frequent with climate change and that often knock out the electricity needed to run many traditional heating systems.

That's why they're often hooked up to places like hospitals that can't afford to lose power.

Queen Elizabeth Hospital is among buildings hooked up to the Charlottetown District Energy System. Such systems are considered more resilient and reliable in case of storms or power outages. (Tom Steepe/CBC)

Ander says Markham's system has had more than 99.99 per cent reliability since it launched in 2000 — in 165,000 hours of continuous operation in 20 years, it's been down just 2.5 hours.

"The buildings are much easier to operate," he said. "You don't need to worry about this critical equipment failing."

He notes there are other benefits for customers:

They don't need to pay the large up-front cost of installing equipment, such as furnaces, boilers, chillers or air conditioners. Nor do they need to maintain the equipment.

They free up space that would have been taken up by that kind of equipment.

There's reduced noise and vibration from heating and cooling systems.

There are safety benefits to not being directly supplied with natural gas, for instance.

Markham District Energy's Markham Centre system serves every new building that has been built in the city's "new" downtown since 2000. It expects to ultimately heat and cool 30 million square feet of homes for 41,000 residents and 39,000 employees in commercial and institutional buildings.

For now, the system burns natural gas and uses electrically powered chillers for cooling, but its use of fossil fuels remains more efficient than if the buildings had individual heating systems. It also has started to incorporate waste heat from data centres .

Installation barriers

Despite the benefits of district energy, most buildings in Canada are still heated and cooled individually. As of 2013, district energy heated and cooled about 2,600 buildings across the country, representing less than one per cent of total energy used for heating and cooling in Canada, reported the Canadian Energy and Emissions Data Centre at Simon Fraser University .

Partly, that's because building an economically viable district energy system typically requires two things that aren't often found together:

High density.

Undeveloped land.

But the biggest challenge is the upfront cost to install the infrastructure, especially since it must be done before there are any buildings with paying customers attached, Ander says, adding that it takes decades of customers paying their utility bills to recover the cost.

"So there has to be some sort of some assistance in some manner from higher levels of government," he suggests.

Biomass boilers burn locally sourced wood chips to heat homes via a district energy system in Teslin, Yukon. One of the co-benefits is it allows money that was previously spent on imported diesel to circulate in the community and provide local jobs, proponents say. (Nelly Albérola/Radio-Canada)

Another challenge is the low price of natural gas that is the dominant heating fuel in Canada, says Lucio Mesquita, senior engineer with the Solar Thermal Renewable Heat and Power Group at Natural Resource's Canada CanmetENERGY Research Centre.

"To compete with natural gas — it's a tough one."

Mesquita was part of the team that built and continues to monitor the Drake Landing Solar Community in Okotoks, Alta., which collects heat using solar panels in the summer and stores it for home heating use in the winter. In the past 13 years, more than 90 per cent of home heat — 100 per cent some years — has come from the solar collectors.

He says not enough of the discussion on reducing emissions has been about ways to decarbonize heating in Canada.

"We have the solutions. We have the technology to do the deep decarbonization," he said. "It's a matter of resources and the right market conditions."