Center for the Built Environment

The David Brower Center (DBC) is a 4-story 45,000-ft2 office building located in downtown Berkeley, California (Figure 1). The building was completed and first occupied in May 2009. It contains lobby and public meeting space on the first floor and open plan office spaces on the 2nd-4th floors, which primarily house non-profit environmental activist organizations. Integral Group (formerly Rumsey Engineers) was the mechanical design engineer on the project and, working with the architect (Solomon E.T.C. – WRT) and other design specialists, put together a design promoting low energy consumption.

 The goal of a low energy building was achieved through an integrated design process that combined thermal mass, shading, and insulation into an efficient building envelope, implemented daylighting and efficient lighting control strategies, and used a low energy HVAC system. The primary space conditioning subsystem is hydronic in-slab radiant cooling and heating, which is installed in the exposed ceiling slab of the 2nd – 4th floors of the building. Due to their larger surface area and high thermal mass, slab integrated radiant systems use relatively warmer chilled water temperatures, making them well-matched with non-compressor-based cooling, such as cooling towers. In addition to the improved efficiency of transporting thermal energy with water vs. air (about 7 times more efficient), the building cooling energy savings are attained through the utilization of a cooling tower, instead of a chiller, to make cooling supply water.

CBE selected the Brower Center as a field study site because it represents a good example of a radiant cooling system using a chilled hydronic ceiling slab design. The main goals of this case study are: 1) to assess occupant satisfaction with the building using CBE survey methods; 2) to analyze the energy consumption of this high performing building; and 3) to set up and begin a more detailed evaluation of the controls and operation of the David Brower Center and to identify strategies for improving system performance in terms of energy use and comfort.