The idea of precooling and demand limiting is to precool buildings at night or in the morning during off-peak hours, storing cooling in the building thermal mass and thereby reducing cooling loads during the peak periods. Savings are achieved by reducing on-peak energy and demand charges. The potential for utilizing building thermal mass for load shifting and peak demand reduction has been demonstrated in a number of simulation, laboratory, and field studies.

In a preliminary case study in a government office building in California in summer 2003, it was found that a simple demand-limiting strategy reduced the chiller power by 80%- 100% (1-2.3 W/ft², 11-25 W/m²) from 2 p.m. to 5 p.m. without causing any thermal comfort complaints. This paper describes a follow-up study in 2004 in which tests were performed in two office buildings over a wider range of conditions. A Web-based comfort survey instrument was developed and used in the field tests to assess thermal sensation, comfort, and perceived productivity ratings in these two buildings.

Units: Dual