Achieving LEED Silver with Metal Frame Construction

Mission Walk is a development by Berry Street LLC—an affiliate of BRIDGE Housing Corporation—and the San Francisco Redevelopment Agency (SFRA). “This workforce housing is for folks who earn too much to qualify for low income housing but not enough to buy market rate housing in San Francisco,” says Richard Stacy, FAIA, Leddy Maytum Stacy Architects (LMSA), the San Francisco-based firm that designed Mission Walk.

[Mission Walk was featured in MHN Magazine’s May issue. Click here to read “Development & Design: Staying in San Francisco.”]

Mission Walk is on track to being certified LEED Silver. The paperwork has been submitted and the project team is waiting to hear back from the USGBC. Does it cost more to go for LEED? The associated architect did charge a fee to coordinate the LEED documentation. “There’s also the commissioning cost which is always the biggest hurdle,” adds Stacy. “A commissioning agent had to be hired.” But in terms of design costs, there was no impact.

“We didn’t design it any differently—we believe in doing sustainable design whether it’s LEED or not,” says Stacy. “Other than the photovoltaic system on the roof, the rest is just good building practices such as observing water conservation and indoor air quality guidelines. In California, a lot of that is mandated by the state anyway,” says Stacy. “You’re half-way there just by following the state’s requirements, like the energy code and limitations on plumbing fixtures, water use and those sorts of things.”

This architectural team also focuses much attention on indoor air quality whether the project is being built to LEED criteria, Green Points or no formal certification program at all. These days ventilation is more important than ever because building envelopes have tightened up so much for energy efficiency as well as waterproofing reasons.

“All of our multifamily developments have an active ventilation system at all times. We build in a system for delivering low level, constant ventilation to every apartment because it makes for better air quality, prevents mold issues and is fairly energy efficient,” adds Stacy. “This we would do anyway, but it also has sustainability benefits.”

Mission Walk is a metal frame building which, according to Stacy, is not that common in California. One of the discoveries made during this project is that it’s difficult to control air flow between units because the framing is so porous—unlike wood framing which prevents air from moving through the wall.

“One of the LEED requirements,” says Stacy, “is to control tobacco smoke from getting from unit to unit and that was a challenge with metal framing. We had to do a series of blower door tests in order to see whether the units were leaking. We found in the first test that the walls were leaking quite a bit. We then developed an elaborate system for caulking and sealing. That is a LEED prerequisite. So to get our LEED rating we had to pass.”

The decision to use steel framing was made early on, and The San Francisco Redevelopment Agency agreed that they wanted to go this route. Metal is less likely to develop mold, shrink or cause cracking issues and it’s recyclable at the end of the building’s life. According to the World Steel Association, this material’s unique magnetic properties make it an easy material to recover from the waste stream so it can be recycled. The properties of steel remain unchanged no matter how many times the steel is recycled. Therefore it is one of the world’s most recycled material.

For the Mission Walk team, using steel in a San Francisco multifamily project resulted in an interesting learning curve. “In the end it all turned out well,” says Stacy, “but there was some extra effort to get there.”