Castle Square Apartments occupies an entire city block in Boston’s South End. A product of urban renewal, this 1960s property looks like buildings all across the country. Seven stories tall, it is brick with concrete infill and no insulation in the walls (R-3) and minimal insulation on the roofs (R-20). There is extensive air leakage between apartments and the outdoors and between the apartments and each other. The windows are poorly insulated aluminum sliders (R-1.7). There are four central boiler rooms (each serving 48 apartments) with large, oversized atmospheric boilers and indirect hot water heaters. Apartments have hydronic baseboard heat. There is no pipe insulation. Each apartment has an individual inefficient through-the-wall air conditioner (9.9 EER). Refrigerators and lighting are above average in terms of efficiency, because most were replaced in 1992 with Energy Star products. Before the renovation, residents’ two largest complaints were 1) poor ventilation and 2) uncomfortable conditions (either too hot or too cold).
Before the renovation, electricity and gas at Castle Square Apartments (192 apartments) cost $590,000 per year. This breaks down to $194,000 (127,000 therms of gas) for heat and hot water and $397,000 (1,974,000 kwh of electricity). Overall energy consumption (including gas and electric) was 13.26 BTU per Square Foot per Heating Degree Days. Residents pay for electricity in their apartments and the property pays for heat and hot water. Before the renovation, the property’s energy use would be considered relatively average compared to other buildings of its age.
Annual Gas Usage Before

Annual Electric Usage Before


Castle Square gas usage before was heat dominant.
