“Simply replacing fossil fuel-powered equipment with electric components will only go so far toward reducing overall emissions,” Sheff says. “Adding more load to an electric grid that burns coal or natural gas to produce its power is not the ideal solution. Electric components must be added to an existing strategy to make the building as efficient and responsive as possible. Adding variable speed technology to pumps, fans and compressors and using controls technology to operate that system at peak efficiency is key to optimizing a decarbonized building and reducing upstream emissions, as well.”
For many examining the concept of decarbonizing buildings, the key is electric—specifically electric power that is generated by renewables, like wind and solar. A move away from sources that burn fossil fuels and toward renew- able electricity could change the game in the fight against climate change.
“The biggest trend lately has been to go fully electric as an energy source for heating and cooling in buildings,” Podesky says. “This is often done with variable refrigerant flow heat pumps. We are taking this approach on most of our building projects in Boston, where the city is pushing electrification. In one particular project, the one system in the building that is not electric is the domestic hot-water system, which is natural-gas fired. For larger multifamily developments, the technology isn’t there yet for large electric water heaters with short recovery times. Also, the operating cost for electric systems would be higher than gas at current utility rates.”
“It’s important to optimize and always question,” Booth says. “I question my own engineers and clients about HVAC. Do you need that much? Are we oversizing that? The usual approach is to oversize and say we’re better safe than sorry. That needs to change. I think it’s important to ask at every level, ‘Is this the right solution?’.”
Challenges
With the push to decarbonize the built environment, the momentum is not infinite and there are headwinds. The main one is economics. Although sustainable strategies can often deliver excellent return on investment, there are costs and, in the end, budget is still king in much of the design and construction industry. But as most climate scientists will agree, the situation doesn’t give us enough time to let the dollar be the driver. Action is needed now, along with some faith in the long-range economics.
“Initial cost is still a huge barrier to decarbonizing buildings,” Sheff says. “The paybacks on these projects are often quick, but their upfront cost can be significant. Even in new construction, where the best decarbonized designs are available, gas-fired equipment is still chosen because of upfront costs, especially in markets where policies are not in place to incentivize decarbonization.”
“Retrofitting HVAC systems in older buildings can be challenging, and first costs can sometimes be a drawback,” Flammia says. “Over time, though, most of the interventions will save money and work toward a safer, healthy environment.”
Initial investment is one hurdle, but another challenge comes from ongoing operation and the fact that our current balance of policy and power generally rewards doing things the way they’ve been done for years.
“Current utilities pricing does not incentivize decarbonization at a large enough scale,” Podesky notes. “As the hot-water system example demonstrates, in many cases natural gas is currently less expensive than electricity. That drives development decisions and ultimately influences how much the building team will focus on decarbonization. But as energy codes become more stringent, building envelopes are getting tighter and better insulated, so heating and cooling systems can be smaller as a result. Hopefully this will combine with technological advances to bring electrical costs more in line with natural gas.”
“Whilst many retrofit solutions cannot be justified on an economic basis purely in terms of energy savings, when you consider the avoided maintenance costs and end-of-life replacement costs in the analysis, there is a strong business case for these systems even considering that gas is currently a third of the cost of electricity,” Booth adds. “In most cases we are very much advocates for optimizing the existing systems before replacement at the end of life or during major refurbishments. We also recommend deferring major equipment replacement until an audit has been carried out (chiller and boiler replacement) to avoid missing an opportunity to switch to a low-carbon solution for little to no additional investment cost.”
Opportunities
In the end, there is great potential for long-term savings on buildings that pursue a path of decarbonization. Market forces, as well as new and evolving technologies continue to shorten the payback periods and make designing a less impactful building easier and more attractive. Improved sensors and building data also give engineers and building operators the tools to make vast improvements in building performance.
“Delving into building data is low-hanging fruit in terms of capital spend, but it does take time and smarts,” Booth says. “Once you’ve optimized the building as far as you can, you may notice systems fighting with each other and being counter- productive. For example, you wouldn’t believe how many buildings are heating and cooling simultaneously. We see a huge opportunity with retrofits.”
“Heat pumps are emerg- ing as the No. 1 technology for replacing gas-fired boilers in buildings,” Sheff says. “Not only do heat pumps reduce emissions, they also lend themselves to variable speed technology, allowing the building’s HVAC system to ramp up and down to meet demand. When this happens, the building is capable of transitioning from an efficient building to a high-performance building.”
“There are amazing new products and research going on in many areas,” Flammia says. “One is a building material made from mushrooms. There are concrete innovations that use fly ash, instead of cement. There are experimental 3D printed buildings made from Hempcrete, which is made of hemp. This is a time that is requiring innovation and a wholesale rethinking of the industry, how we make things and what we value. It is daunting, but it is doable.”