Creative Juxtaposition

A 133-year-old municipal building in Cambridge, Mass., recalls the past, even as it looks forward to an energy-efficient future.
August 11, 2010

Surrounded by history, the residents of Cambridge, Mass., understand the importance of preserving it. But this Boston suburb is also a mecca for high-tech activity.

It is perhaps not surprising, therefore, that Cambridge elected to save a 133-year-old building that serves as a City Hall Annex — and to equip it with the latest technology. This imaginative blend of past and future was recognized with a Grand Award in BD&C's 21st Annual Reconstruction & Renovations Awards.

Built for $30,000 in 1871, the building served both elementary and high school students before becoming the City Hall Annex in 1942. Over the years, the interior was renovated as needed, without a real conversion from its previous use. A decision about the building's future was triggered in 1999, when it was closed after a steam pipe leak spread moisture that resulted in mold infestation.

At about the same time, the U.S. Green Building Council was developing its Leadership in Energy and Environmental Design criteria. Cambridge city fathers decided to "go green," and mandated that all future city buildings would be designed and constructed to LEED criteria.

With the mold problem in mind, they saw the implementation of LEED criteria as a signal that the building would no longer be plagued by poor indoor environmental quality. The city anticipates earning at least Silver (and possibly Gold) accreditation under LEED for Existing Buildings.

The building was vacated for the four years required to perform remediation, assess options, and complete the renovation. HKT Architects, Somerville, Mass., was awarded the design work when the initial firm hired, David Perry Architects, closed shop.

The most significant interior alteration was the relocation of the main entrance from Broadway to the Inman Street side of the building. The original main entrance was at mid-level, requiring a redirection either up or down a half level to get to city offices. Visitors are now greeted by a new lobby with a wide staircase leading up to an art gallery. "Because it is a two-story space, you have a complete sense of where you are and where city departments are located," says HKT project principal William Hammer. As a bonus, previously unusable basement space can now be used, because the atrium allows light to reach areas that otherwise would have been uninhabitable.

 
Once an eyesore to the community, Cambridge’s City Hall Annex has received new life after a $7 million renovation.


Drilling down to save energy

The heart of the building's HVAC system is a groundwater heat pump system that utilizes three 1,200-foot-deep, standing column wells that supply underground water. The wells, covered with manhole covers, are located below the parking lot.

The application is somewhat unusual because it is used in conjunction with a traditional office VAV air distribution system, says Chris Schaffner, project manager with ARUP, the project's mechanical/electrical engineer. In most applications, heat pumps are distributed throughout the building, and installed above the ceiling. The City Hall Annex system's eight heat pumps serve as both chiller and boiler and operate in conjunction with a central air handler. This arrangement provides benefits in terms of maintenance and noise reduction, according to Schaffner.

Efficiency vs. aesthetics

The building's 5,000 sf of roof-mounted photovoltaic panels are expected to produce about 10% of its electrical requirements. The system can generate 27kW of power in full sunlight.

The placement of the panels was scrutinized by the Mid-Cambridge Neighborhood District Commission, which objected to equipment that would rise above the roof level. As a result, the panels were installed flat. The optimum installed angle is the latitude of the location where the panels are used, according to Bill Kanzer of Evergreen Solar, Marlboro, Mass., which supplied the panels. For the Boston area, this is about 40 degrees.

However, the flat installation was "pretty much a prerequisite," says John Bolduc, the city's environmental planner, who notes that only a small part of the installation is visible from ground level.

Direct/indirect pendant lighting fixtures with a self-contained daylight sensor are another energy-saving feature. A relatively new product, they were used throughout the building. Energy codes typically require occupancy sensors, but daylight sensors are normally installed independently, according to Schaffner. This can lead to problems with satisfying the needs of various users, as well as causing integration problems, he says. Employees can turn lights in their area on and off, and control their intensity, through a computer interface. About 90% of the building interior now receives daylight.

The annex is projected to achieve a 44% reduction versus ASHRAE 90.1 (1999). Factoring in the impact of the solar photovoltaic system will push energy savings to more than 50%, Schaffner says.

 
Daylight now reaches about 90% of the building’s interior. Pendant lighting fixtures with self-contained daylight sensors adjust lights according to the daylight level.


A payback period of less than five years was projected for the sum of the building's energy-conserving features, excluding the photovoltaic system, but paybacks on individual items were less impressive. For example, the $143,000 groundwater heat pump system was calculated to have a payback of 10 years. For the photovoltaic system, it would be about 35 years without the $350,000 grant the project received from the Massachusetts Technology Collaborative, a funding source for renewable energy that is underwritten by a charge on electric bills, says Schaffner.

Recyclable materials were used whenever possible. They included carpeting and ceiling tiles made with recycled materials, and wood harvested from FSC-certified sustainable forests.

Education for everyone

Todd McCabe, project manager with general contractor Consigli Construction Co., Milford, Mass., says the project was a true gut rehab that involved extensive demolition, reframing new floors at different elevations, and constructing a new roof. The tight urban site was challenging. "We were working, literally, only 10 feet away from bedroom windows," he says.

The annex was Consigli's first green project. Its employees not only had to learn LEED requirements themselves, they had to educate the subcontractors as well.

By source-separating materials, Consigli diverted about 85% of the project's construction debris from landfills. McCabe says the company made "a 100% conscious effort" to communicate LEED criteria to both field and office employees. It began keeping track of waste recycling achieved on its projects, posting the results weekly and monthly. This generated competition among superintendents to see which project team could achieve the best results. Due to the limited space on the site, Consigli used 15-yard dumpsters rather than the normally used 30-yard units.

For two weeks prior to occupancy, the building was flushed with 100% outside air to remove offgassing from materials inside, as well as dust and construction debris — a specific LEED guideline.

When the building first opened 133 years ago, its large operable windows were heralded for providing ample daylighting and good ventilation — attributes that were diminished over the years as the building was converted from school to office use. The renovated structure now admits a greater amount of daylight to the interior and circulates fresher air. "We're kind of coming back full circle," Bolduc says.

Awareness of the building's greenness has generated pride among city employees and the community, Bolduc says. Neighboring residents, in addition to being relieved that the project was completed, "were happy that the city made this kind of investment and did it well — not just as cheaply as possible."