David Baker Architects


Modular Construction and Sustainability's Triple Bottom Line

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Union Flats features 388 wood-framed modules, craned into place at a rate of 12 per day. Image: OxBlue

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by Dodge Data & Analytics

The case study first appeared in the 2020 SmartMarket Report.


The Union Flats, a 2.4-acre, 243-unit, mid-rise housing development 30 miles southeast of San Francisco, pioneered large-scale modular construction in the region while achieving exemplary environmental performance. Completed in 2018 by developers CityView and Windflower Properties as northern California's largest modular multifamily development, the Union Flats epitomizes the advantages of offsite construction in a tight market. the question for practitioners of green design and development is the degree to which modular construction also enabled the project's LEED Platinum certification.

The vertiginous cost of housing in the Bay Area makes it impossible to forget here that sustainability has economic and social dimensions, as well as environmental ones. "It's quite a struggle right now for those of us in the Bay Area trying to do housing development that is affordable to even middle-income earners," says Windflower CEO Fei Tsen. She cites such constributing factors as the shortage of skilled labor that has resulted from migration out of the recession of 2009, and the inability of housing development, with its lower profit margins, to complete with nearby big tech projects for the remaining workers now commuting two or three hours a day to work in the area. "So it's imperative that we look at prefab and modular," she says. 

Modular to the Rescue

The Union Flats shows what is possible. Its location--only a block from an intermodal transit station--made the development eligible for millions in funding from the Infrastructure Infill Grant Program of the California Department of Housing and Community Development. But that funding mandated a completion date that conventional construction couldn't meet. Modular--with its simultaneous constructin of sitework and superstructure--could. 

The development consisits of 388 wood-framed modules, shipped from Idaho and craned into place--either onto a foundation, atop a Type I podium, or wrapping a Type I concrete parking garage--at a rate of 12 per day. The resulting schedule compression allowed the project to meet its funding deadline, and in that sense made the rest of its achievements possible. 

Designed by San Francisco-based Bavid Baker Architects (DBA), the buidling fronts onto a new civic plaza, edges a landscaped promenade along one site, presents ground-floor front doors to a sidewalk along the other and backs onto an embedded parking garage. Cladding materials include wood, stucco and strips of fiber-cement panels in board-and-batten configuration. The massing is self-shading: At the southwest facade, balconies are recessed; at the northwest and southeast, bays are articulated to provide shade while opening up to daylight and views of the nearby hillls. Helping to foster the casual interactions among neighbors that can build social connectivity, a central courtyard provides a swimming pool and green-roofed pavilions with spaces for leasing, co-working. fitness, events and a dog spa. 

Sustainability Independent of Modular

By beyond that inital enabling schedule compression, how much did modular construction contribute tot he proejct's LEED Platinum achievements? As it turns out, surprisingly little. Reduced waste was the main factor, says Daniel Simons, a principal at DBA. And the mamnufacturer was also able to obtain linoleum florring at a price that allowed the project to substitute it for the VOC-emitting vinyl more commonly used in multifamily housing, which improved the project's indoor air quality. But, in general, says Simons, "most of the things that we did that made the project more sustainable were independent of it being modular."

The Union Flats was DBA's first modular project. The firm now has another almost complete, and four or five more in design or about to start construction. "We've learned a lot since the first one," says Simons. "It was definitely a bit of a proving ground." Even so, he says that the environmental opportunites that were missed on this project--and that continue to be missed in modular construction more generally--"mostly come from sustainability not yet being on the radar of the facotires as a benefit." Modular manufacturers know that it is the method's timeand cost savings that are selling their products, he says, so their research and development efforts are aimed at improving those outcomes even further. Now, however, he sees some manufacturers beginning to realize that prioritizing sustainability can open up more opportunites. 

Room for Improvement

Top of Simons' wish list is healthier materials. DBA's efforts to improve the quality of materials in their multifamily projects are often stymied by a lack of product ingredient transparency, a lack of choice, prohibitive costs or a combination of all three. Unlike the office sectior, where money-backed research and advicacy has been able to improve materials transparency and health, "that hasn't really happened with multifamily hosuing," says Simons. 

But while individual hosuing developments may lack acess to the economies of scale that have allowed corporations building millions of square feet to advance materials health in the office sector, modular facotires may have an opportunity. "They've started getting purchasing agreements with manufacturers because they know they're going to need a lot of this stuff, and so they know they can get good pricing," says Simons. "But they haven't taken steps to say, 'not only can we get good pricing, but we should also push for PVC-free flooring and other materials health priorities that could be on our radar.'"

Another sustainability advantage fabricators could offer lies in their tighter control of quality standards. " The quality of multifamily construction is variable, to put it generously, in terms of quality of insulation installation, thinking through thermal breaks and even down to mechanical systems," says Simons. He sees these areas where modular fabricators could leverage their factory-based methods and growing market options available to the multifamily sector. "If it becomes a facotry standard, we could bring in more advanced technologies to help with energy efficiency and ventilation at prices that are accessible," he says. "There's a bunch of areas  like that where multifamily housing isn't very sophistocated, and modular could help."

Such improvements will come too late for the Union Flats. Nevertheless, the project's parallel achievements--in pioneering large-scale modular development and attaining LEED Platinum certification--stand as a milestone for the multifamily sector. They demonstrate how modular construction's schedule and labor market advantages can help get an environmentally and socially progressive project built and contribute to sustainability's triple bottom line.