Lowering carbon emissions from the building sector is critical to mitigate climate change impacts. To achieve a decarbonized economy, interest in building electrification is growing with modern high-performance buildings moving towards all-electric mechanical systems.
“In B.C., the main way to reduce carbon is to use electricity. Natural gas is 17 times more carbon intensive than electricity. That’s why decarbonization equates with electrification,” said Andy Chong, managing principal at Integral Group, who shared insights on building electrification in a session for Buildex Vancouver.
He started with the rationale for the trend toward electrification, discussing the evolution of building codes and the need to reduce cost and energy. The trend and conversation today is about reducing carbon emissions and fuel switching (from fossil fuels to electricity) is a necessary step to meet climate action goals.
He cited an IPCC special report on the global impacts of 1.5 °C warming above pre-industrial levels, noting that all three levels of governments in Canada are missing the mark despite setting climate change targets.
“We’re cruising past 1.5 °C. Whether you believe that’s important or not, carbon is a conversation right now,” said Chong.
When looking at electrification of building mechanical systems, Chong said it’s about satisfying end uses of energy with electricity that were coming from somewhere else such as cooking and space heating. Furnaces and boilers constitute one of Canada’s largest sources of carbon pollution.
“Decarbonization is an unavoidable theme in our industry right now,” he said. “In B.C., under specific conditions, it means weaning ourselves off fossil fuels for the end uses in buildings that electricity can be used for.”
The biggest challenge is electricity is expensive. “If making a decision purely on operation costs today, it’s hard to make those numbers work,” he acknowledged. “But when we look at carbon cost – it’s huge. There is a huge difference [with using electricity] against even the highest efficiency gas systems in terms of carbon.”
He cited a hypothetical 100,000 square foot commercial building as an example, illustrating that electricity annual cost is three times more than high efficiency gas. But in terms of carbon emissions, electricity is significantly lower at 17 times. Heat pumps offer even more carbon reduction.
Heat pumps are an important technology in the push to decarbonize. Chong provided an overview of how heat pumps work and the different types of pumps available: air to air, air to water and water to water.
“Are we ready to move from fossil fuel appliances to all electric systems? Combustion is really simple and convenient and cheap. Boilers are dead simple at their core,” he said. “Heat pumps are complicated.”
Performance, complexity, operating costs, reliability, maintenance, and limitations in cold-climates are some of the challenges with heat pumps.
“It’s important that we don’t treat them as oversimplified, silver bullet, black boxes connected to a pipe in the ground with unlimited energy. They’re not,” he cautioned. “They are a great application – great solution to some of the problems that we have but they take some sophistication to do right.”
Making heat pumps work requires following best practices with careful treatment of compressors being a priority.
“Compressors are the heart of a heat pump system and we have to treat them well. We need to design and specify with redundancy, backups and maintenance in mind,” said Chong, advising to purchase equipment that comes with service and 10-year warranty for compressors.
For a 100 ton heat pump system, he recommended using 10×10 modules where compressors can be worked intermittently (and not overworked) to meet fluctuating heating and cooling loads.
“Another easy solution is to put in a buffer tank. The buffer tank strategy is simple and will save your compressors,” he said.
Heat pumps also need a better robust cold weather strategy because they don’t “like operating in cold.” Chong cited a project where the heat pump was connected to two sources of energy as a cold weather strategy: an air heat source pump on the roof is used in warm weather while a geothermal field under the parkade is used in cold weather.
Another tip was to be opportunistic with energy sources. Chong highlighted example projects such as the sewage waste heat recovery at Olympic Village; heat recovery from the data centre for Telus Garden; and heat recovery from product refrigeration systems at a Whole Foods store in Victoria.
“Refrigeration loads are a great source of energy. Heat rejected can heat other buildings on site or go back into heating system for make-up air,” he said about the Whole Foods project.
Synergies with other high-performance building technologies can help maximize heat pump performance. Many radiant heating systems are coupled with heat pumps because of their lower design temperature. The lower the design temperature, the higher the performance of a heat pump, explained Chong.
“Pairing a heat pump system with a good building envelope and a lower temperature application like radiant systems is a match made in heaven,” he said. “The heat pump is there to replace the heat you are losing through the skin of the building in the first place. Reducing the demand for heat pumps in the first place is super key.”
He concluded by saying: “Heat pumps can be a very efficient part in decarbonizing and electrifying our buildings. But if you use a heat pump, it’s not an unlimited black box of energy.”
Cheryl Mah is managing editor of Construction Business.