This preliminary study explores the impact of various design assumptions on the supply fan energy consumption of pressurized underfloor plenum systems as compared to that of traditional overhead constant air volume (CAV) and variable air volume (VAV) systems.

The results of this study indicate that, in terms of optimizing energy efficiency, variable air volume (VAV) control of supply air is the preferred method of cooling perimeter zones of pressurized underfloor air distribution (UFAD) systems just as it is for overhead (OH) systems. Moreover, cooling fan energy consumption for underfloor VAV systems can be significantly less than that for overhead VAV systems. Results show also that constant air volume (CAV) systems can be an effective approach for zones, such as core areas, that have little load variation (assuming oversizing is minimized). For these situations a UFAD-CAV system can offer low installed cost, simplicity, and provide modest energy savings compared to an overhead VAV system.

The design of many unconventional internet and technology office spaces in the late 90’s has challenged many standard conventions of workplace protocol. Although it is easy to poke fun at the free café lattes, foosball machines, and dogs in the office, the desire to create a workplace that is healthier, more functional, and casual is seen by many as a positive and continuing trend. The question then arises, how well do these new innovative workplaces actually perform?

The Teledesic Broadband Center, in Bellevue, Washington, is one example of this new office paradigm. Designed by the architecture firm NBBJ of Seattle in conjunction with mechanical engineering firm Arup of San Francisco, the project is an adaptive reuse of an industrial building to create the new headquarters for Teledesic, a company that is building a global broadband communications network. The design of the 70,000-square foot space incorporates many new workplace features, including a high loft-style ceiling, an open workstation plan, an open mezzanine, and an underfloor air distribution (UFAD) system that allows occupants to control the airflow to their individual workstations.

A field study of the Teledesic offices was conducted during the winter months of 2000/2001 to gain both quantitative and qualitative insight into the building’s performance. This study, carried out by researchers from the Center for the Built Environment (CBE), included several specific research objectives:

1. Assess occupant satisfaction and comfort.

2. Evaluate the operation of the underfloor system.

3. Assess the underfloor system energy performance.

4. Understand the interactions between building design characteristics and the underfloor system.

5. Investigate the thermal stratification in the high ceiling area.

The study included two site visits for detailed observation and data collection, an on-line survey of the building’s occupants, and interviews with the project design team. During the first site visit the research team gathered building and occupancy information and installed automated sensors that would record air temperatures at multiple locations over a six week period. During a second visit the research team retrieved the sensors and collected data, and made final observations. Measurements of the indoor environment using hand held equipment were made during both visits