10 May 2018

Largest zero-energy office building in the Southeast U.S. planned in Raleigh

Written by Jim Pierobon

A proposed 10-story office building in Raleigh, North Carolina is set to become the largest zero-energy structure in the Southeast U.S. and could boost construction of green high-rises for commercial tenants throughout the region.

City Gateway, developed by SfL+a Architects in Raleigh, North Carolina, is designed to produce about 20% more energy than it uses by how all of its systems – electricity, ventilation, windows, foundation and insulation – work together, says CEO Robbie Ferris.

City Gateway, planned for Raleigh, NC by SfL+a Archtects, is designed to generate 20% more energy than its tenants are projected to us. CREDIT: SfL+a

At the outset, among the City Gateway private tenants will be businesses choosing to work with Sfl+a on additional zero energy structures and the charter Exploris School.

“I’m thrilled they’re combining mixed-uses and being a progressive leader in Raleigh,” said Cathy Higgins, director of research at the New Buildings Institute, which tracks zero-energy structures throughout the U.S. “Energy-positive design is an important technology in the efforts to create a more sustainable built environment,” she said.

“We are seeing more architects and engineers pursue energy-positive buildings because they recognize the urgent need to address climate change and create more resilient buildings,”  Corey Enck, vice president of Leadership in Energy and Environment Design (LEED) technical development for the U.S. Green Building Council.

City Gateway, Higgins said, is “the first in the Southeast of this type to reach this ambitious level.” Once completed, she said it stands to be one of about a dozen mid- or high-rise zero-energy structures in the country not designed for and occupied entirely byand for non-profit organizations and government agencies.

How private architects and developers in the Southeast move to zero out utility energy costs is being closely watched by developers, leasing agents, environmental advocates and policy makers. Can Raleigh and other Southeast cities trying to score points for sustainability begin to catch up with cities in California and elsewhere with dozens of zero-energy buildings for all types of tenants to their credit?

“When you share what the potential is in terms of operating expenses and the technologies that are being provided, (leasing agents) are very excited about it,” said Arnold Siegmund, a principal in the Avison Young leasing firm in Raleigh.

Nationally, the New Buildings Institute counts 520 zero-energy structures in its database. The tally is rising every year. “There used to be about 20 practitioners (architects) doing roughly 60 zero-energy buildings in 2012,” Higgins said. “Now there are a couple hundred firms doing so.”

Origins of ‘zero-energy’ buildings  

Depending on whom one talks to, the concept of a zero-energy building began drawing attention in the U.S. and Canada after the 1973 Arab oil embargo. By many accounts it didn’t take root until American Physicist William Shurcliff published a book – The Saunders-Shrewsbury House – articulating the benefits of a “passive house” for residences in 1982.

SfL+a has nine zero-energy buildings in operation with two more under construction. All are one- or two-story structures. It is well known in North Carolina for designing and building the Sandy Grove Middle School in Fayetteville, North Carolina.

The energy needs at City Gateway are to be met by a geothermal heat pump system and about 4,000 fixed Sunpower solar modules with a capacity of 1.4 MW secured on two canopies (image).

Geothermal systems circulate a fluid from a network of underground pipes into and throughout the building to capture subsurface heat in the winter and cooler subsurface temperatures in the summer. A diesel generator will back up the geothermal and solar systems. The building will be connected to the local grid.

Reducing peak demand is key

A key to generating more power than the building needs is how the building will reduce its peak demand level. That’s because many utilities, including Duke Energy in Raleigh, sets a fixed charge every month regardless of how much electricity a tenant uses. Actual usage of electricity is billed in addition to that.

Tenants’ energy costs will be included in the rent they pay and are to include incentives for conserving energy on their own. “This may be in the form of energy credits or an (added) cost if energy-use goes above a pre-determined threshold,” said SfL+a spokesperson Danielle Davis.

Occupants will further benefit from radiant concrete flooring and ceilings along with electric chrome and glass to deflect heat off its occupants. An air-cleaning system similar to what’s deployed in submarines will clean and circulate the indoor air.

“Most of the contaminants” humans are exposed to Ferris said, “come from human beings. It’s not just CO2 from outside. We’ll bring in some outside air but a lot less than we would need otherwise.”

The cost to build City Gateway is estimated to be $225 per square foot, or about $77 million. Once financing for the building closes soon, lease terms to be offered on the 175,000 square feet of usable office space will be “at market terms for Class A office space” or about $34 per square foot for a seven-year lease, according to Davis.

Critical to achieving the building’s optimal performance and comfort, Ferris said, is how it operates during its first three years.

“Most buildings don’t work as designed,” Ferris said. “With energy-positive buildings, you’re measuring all it automated systems. If it’s not working as designed, you fix it.”

Ferris contrasted that with developers who sell the buildings they develop soon after the reach near or full occupancy. In the process they step back from witnessing how it operates, garnering feedback from tenants and tweaking the numerous systems to consistently achieve optimal energy efficiency and comfort levels.

Raleigh’s energy costs a factor in calculating ROI

Because developers in California have a compelling incentive to zero out the relatively high costs of energy supplied by utilities, investments in green buildings are often easier to justify on economic grounds. Because energy costs are lower in North Carolina that is a taller hurdle to clear when calculating a tenant’s return-on-investment.

The businesses and a charter school that have pledged to occupy the City Gateway project comprise about two-thirds of the 85,000 square feet of usable space. The remaining 30,000 square feet is earmarked for parking.

Construction is to begin once financing and all permits from the City of Raleigh are in place, expected early this summer. The elementary school and allied businesses have been told they could expect to move in as early as the 4th quarter of 2019.

Leave a Reply