NBI Completes Study into Energy Performance of Commercial Buildings with Radiant Systems for Cooling and Heating

During the renovation of the Edith Green Wendell Wyatt Federal Building, a variable air volume (VAV) system was replaced with a radiant design system. The design team included numerous CBE industry partners, including SERA Architects, Stantec, Interface Engineering, and Charles M. Salter Associates. Image copyright Nic Lehoux Architectural Photography.

Read the radiant energy performance report here.

New Buildings Institute (NBI) has partnered with U.C. Berkeley’s Center for the Built Environment (CBE) to provide valuable insights into the effectiveness of radiant cooling and heating systems. These systems are a promising new HVAC technology which is increasingly being used in commercial buildings seeking ultra-low and zero energy outcomes. NBI led the energy study as part of a multi-pronged research effort focused on optimization of radiant systems for energy efficiency and comfort. The study was led by CBE on behalf of the California Energy Commission’s Electric Program Investment Charge (EPIC) program.

This research represents the largest dataset of measured energy use from buildings with radiant systems for both cooling and heating. While forced-air distribution systems remain the predominant approach to heating and cooling in U.S. commercial buildings, radiant systems are emerging as an integral part of high performance buildings. Radiant systems transfer energy via a surface that contains piping with warmed or cooled water, or a water/glycol mix. This study focused on radiant floor and suspended ceiling panel systems[1]. These systems can contribute to achieving significant energy savings due to relatively small temperature differences between the room set-point and the cooling/heating source, and the efficiency of using water rather than air for thermal distribution[2]. The full research study included a review of the whole-building design characteristics and site energy use in 23 buildings, and surveys of occupant perceptions of indoor environmental quality for 26 buildings involving 1645 individuals.

The completed energy performance report provides an analysis of measured energy use, compared to standard benchmarks, for 23 buildings in North America with radiant systems for both heating and cooling (including descriptions of each building — type, size, location, climate zone, etc.). The study found that nearly all the buildings outperformed similar buildings and national benchmarks, suggesting that when radiant systems are part of an integrated design approach, they can lead to lower energy consumption.


Cathy Higgins, Research Director


[1] Thermally Activated Building Systems (TABS) and Embedded Surface Systems (ESS) are located in the floor. Note: Chilled beams also use water distribution but typical ‘active’ beams provide cooling predominantly via convection by blowing building ventilation air across cooling coils, and were not the focus of the study.

[2] Water transfers thermal energy about 7 times more effectively than air. (CBE Brower Study, CEC EPIC 2011 http://escholarship.org/uc/item/7tc0421f#page-1)