Carbon Reduction Begins With the Building Envelope

As they get set out to comply with New York City’s ambitious Climate Mobilization Act – which will require most buildings to sharply reduce carbon emissions in coming years – many co-op and condo boards are mulling retrofits such as installing LED lights, solar panels or a cogeneration system, maybe switching the boiler from oil to natural gas. Such thinking is exactly backward, according to a new book, The Power of Existing Buildings: Save Money, Improve Health, and Reduce Environmental Impacts. 

“This book is a step-by step strategy how to achieve zero energy or low-energy consumption through deep energy retrofits,” says co-author Craig Stevenson, president of the Auros Group, a sustainability consultancy. Stevenson and his co-authors, Beth Eckenrode and Robert Sroufe, dismiss LED lights and solar panels as “low-hanging fruit.” Instead, they argue, owners of multifamily buildings should adopt the “holistic” approach to retrofits present in passive houses. Under this system, first developed in the 1970s, the top priority is to improve the entire building envelope – roof, walls, windows, doors, foundation – so there is no “thermal bridging,” the loss of heat or cool air through gaps in the envelope. 

“In traditional buildings, when you have a leaky envelope the mechanical systems are set up so they pressurize the building, and you’re pushing all the heat and the cooling you just purchased through your walls,” Stevenson says. “In a passive house, you do have cooling and heating elements, but you might never have to turn them on. The ventilation system is cheap and super-efficient with 30 percent greater ventilation than the current requirements, and the air goes through a heat recovery system.” 

Most existing buildings can be insulated from the outside, using modular, prefabricated panels created by technology developed in the Netherlands. The authors of The Power of Existing Buildings liken the process to putting a “sweater” on the building: “With its new ‘outfit,’ the building has enhanced market appeal, lower utility costs, and superior air quality. Insulating from the outside is generally an easier process than interior insulation.” An added advantage is that residents can continue living in their apartments while the insulation is installed. 

Once the envelope is tight, all the systems in the building will become much smaller and more affordable. Only then is it time to install renewable energy sources, such as solar panels or cogen systems. “If you’re using less energy for the systems because those systems are now smaller, the onsite energy generator is also that much smaller and affordable,” Stevenson says. “Instead of putting solar panels on the entire roof, one can put up a small, affordable array. People who are looking at renewables first will find it’s not really a good financial decision. They over-purchases onsite generation because they have not dealt with efficiency first.” 

Stevenson is on the board of directors of the North American Passive House Network, which will provide any building owner with information about financing and resources. The New York State Energy Research and Development Authority offers significant incentives for passive-house-certified residential buildings. Information and tips on financing and incentives are also provided by the nonprofit Building Energy Exchange. 

While passive buildings, both new construction and retrofits, are booming across the U.S. and Europe, the concept might still sound like a stretch to many New York co-op and condo boards. It shouldn’t, says Stevenson: “If building owners identify their goals and will throw some financial metrics against those goals, then they would be incentivized into this holistic performance of their building.”