Newland Apartments, Malden, MA Housing Authority
Malden Housing Authority Brings Cutting-Edge Energy Efficiency to Postwar Apartment Complex
In the broad maintenance garage abutting the boiler house for the Newland Apartments in Malden, Massachusetts, a yellowing and much-handled map traces the path of the heating system’s underground distribution loop, a complex, meandering line that swings like a river’s oxbow from the boiler house, through a network of 62 buildings, and back again. Mark B. and George C., Siemens Project Developer and Senior Project Manager respectively, regard the map with respect; it’s at once the record of an impressive engineering achievement, hastily yet thoughtfully put together in the wake of the housing shortage after the Second World War, and a documentation of a current problem: today, that loop is failing.
“It leaks in too many places,” Mark B. says. Worse, even in the best of times and with appropriate insulation, the buildings on the return portion of the loop never received as much heat as those closest to the boilers’ output. The property owners, the Malden Housing Authority, were faced with an exceptionally expensive rebuilding project that would buttress an uneven—and by contemporary standards—woefully inefficient system for providing heat and domestic hot water.
A decentralized approach to efficiency
Fortunately, Siemens presented a much more attractive alternative. Under a performance contract model, Siemens finances, designs and oversees the construction of a new heating infrastructure; further, Siemens guarantees fulfillment of the Housing Authority’s performance and cost-savings targets, transferring risk from the client to itself.
George C. leads the way through the apartment complex, pointing out the most outwardly visible change in the new design: compact huts, much like tool sheds, that now dot the campus—nine 8’ x 10’ sheds serve single buildings; twenty-seven 8’ x 14’ units serve two buildings each. Inside these sheds—so unimposing that George C. refers to them as “dog houses”--each building gets a dedicated boiler and domestic hot water tank; these replace the three massive sectional, cast-iron, oil-burning boilers in the boiler house, and the house’s 2,000 gallon water tank.
The distribution of heat and hot water among these dog houses resolves the distribution piping problem by simply eliminating its need. But the bigger accomplishment, the achievement of greater energy efficiency, is fulfilled through the intelligent application of cutting-edge technologies.
“We started with the envelope,” Mark C. says. “We insulated, added weather stripping, and sealed gaps. For the water, we replaced the sink aerators and brought in new shower heads.” By making these improvements first, Mark B. and George C. accurately sized the complex’s heat and hot water needs.
At the heart of the new system, Siemens has installed 212 MBH condensing boilers that provide heat for each building and each of the new indirect hot water tanks. The smaller doghouses that serve one building get one of each; the larger sheds that serve two buildings get two. The latter take advantage of a lead-lag installation that allows a single boiler to provide heat and hot water to both buildings under low-load conditions, such as the shoulder seasons that surround the high-demand winter months.
Inside the doghouses, the new units look deceptively unprepossessing. The water tanks appear a bit wider than usual due to the ample application of insulation. But the boilers, suspended on steel racks mounted to the wall, seem impossibly small, more like a dormitory mini-fridges than traditional boilers. Looks deceive: inside, each element of the boiler has been engineered, not only to work at optimal efficiency, but to sustain long-term performance and facilitate easy maintenance. The Lambda Pro combustion controls “read” flames in real time, and can make instant adjustments to account for variations in fuel quality, combustion air temperatures and changing draft conditions. The heat exchanger, crafted in the highest quality, titanium stabilized stainless steel available, is built for twenty year and more lifespans. All internal parts and connections are readily accessed by merely removing the outer shell, making routine cleaning a snap.
Under the old system, the boilers maintained a primary loop temperature between 160° and 180°F; residents (there are four to six units per building) had no control over their indoor temperatures. The new system, however, simultaneously allows greater overall control of loop temperature while giving tenants the power, via new thermostats and radiator controls, to adjust their home temperatures within a range from 65° to 74°F. Today, outdoor temperature dictates loop temperature on a reset schedule which allows the Housing Authority to adjust for improved efficiency.
Wring out every degree of heat
Cutting-edge condensing boilers bring the potential for great energy savings; the overall design, including the innovative application of complementary technologies, ensure that their potential is realized. Paul Ross, president of Hydronic Alternatives, collaborated with Mark B. and George C., to introduce system components that would collapse the return water temperature as much as possible. In addition to ensuring that the apartments capitalize on the heat that’s created, the reduced return temperatures maximize the condensing potential on the exchangers, driving the boilers to peak efficiency.
“We’re using state of the art, Grundfos Magna3 pumps for circulation,” notes Ross. “These variable frequency pumps, or VFPs, not only reduce electricity consumption by seventy percent, they adjust to pressure and temperature automatically.” By facilitating the lowest flow rate necessary, the pumps also help the system draw more heat from the loop.
Similar “heat sinks” serve double-duty. The doghouses themselves are heated by passive radiators that draw energy from the return water while preventing system pipes from freezing. An additional heat exchanger on the return pre-heats city water before going into the DHW domestic hot water tanks, wringing out more degrees of heat and reducing the energy load for domestic hot water.
Construction began in the fall of 2014, with full conversion anticipated in the early spring of 2015. Given the promises it is contracted to fulfill—for both reduced energy usage and dramatically increased cost savings—Siemens has its reputation and its profits on the line. But Mark B. has every confidence in the project’s success. “We do two things,” he says. “We buy high-end equipment, and we hire high-end installers. The end result is a win for everyone: us, the Housing Authority, and most importantly, the residents.”
-- George C. & Mark B.
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