Upgrade in Sustainability: Medford Housing Authority’s Saltonstall Building
Thursday, January 20, 2011
The recent installation of a “Solar Thermal Domestic Hot Water System” and the replacement of the existing electric baseboard heating system with a high efficiency hot water system at the Saltonstall Building is the latest achievement of R.W. Sullivan Engineering in its commitment to sustainable design.
The Saltonstall Building – located at 121 Riverside Avenue in Medford, Massachusetts – consists of approximately 200 apartments located on floors 2 through 11, as well as administration areas and common areas on the first floor. This high-rise is the largest of Medford Housing Authority’s properties.
The new Solar Thermal Domestic Hot Water System is expected to provide a minimum of 250,000 million BTU annually, which is approximately 45% of the domestic hot water load for the building. An array of 1,600 square feet of evacuated tube solar collectors were installed on the roof of the building. Two 1,200 gallon storage tanks, two stainless steel heat exchangers and several pumps were installed in the lower level mechanical room. The system is controlled by a state-of-the-art control system that exceeds National Grid’s rebate monitoring requirements. The performance of the system can now be monitored through the internet.
In addition, the replacement of the existing electric baseboard heating system with a new high-efficiency hot water system is expected to reduce Medford Housing Authority’s annual utility cost by around $80,000 and substantially reduce their carbon footprint. The project consisted of the removal of the electric baseboard and installation of the hot water baseboard in all 200 apartments. Hot water is generated by a state-of-the-art boiler plant which consists of three, 1,300,000 BTU per hour Lochinvar Sync boilers (up to 98% efficient), two high-efficiency pumps, and Variable Frequency Drives (VFD). The system is controlled by a Tekmar control system that varies the system temperature based on the outdoor air temperature and modulates the hot water flow based on the system demand.
The projects’ costs were approximately $310,000 for the installation of the solar thermal system and $1,241,000 for the replacement of the heating system. With RWS’s assistance, the two projects respectively received a $159,000 grant from ABCD Inc. and a $32,000 grant from National Grid as part of the MASS SAVE utility program. Both projects were fully functional by January 2011.
