Project Title:

Optimizing Radiant Systems for Energy Efficiency and Comfort

Creating standardized guidance for design and operation of efficient radiant systems.

Status (updated 6/16/2017): Ongoing

Funding sources: California Energy Commission EPIC, Industry In-Kind Support, and CBE Industry Consortium

Project Objective

Radiant technology, while representing a commercialized technology, is still predominantly unfamiliar to the building design and operation industry at large. The overall goal of this project will be to address needed enhancements to radiant technology by developing the following: (1) sizing and operation tools; (2) energy, cost, and occupant satisfaction data; and (3) Title-24 and ASHRAE Standards advancements.

Significance to Industry

Radiant cooling and heating systems provide an opportunity to achieve significant energy and peak demand savings compared to conventional all-air systems. As a result, application of these systems has increased in recent years, particularly in zero-net-energy (ZNE) and other advanced low-energy buildings. Despite this growth, our experience in completed installations to date has demonstrated that controls and operation of radiant systems can be challenging due to a lack of familiarity within the HVAC design and operations professions. Recent research from CBE has shown that the fundamental differences between radiant and all-air systems require new and/or revised definitions and methods for the design, sizing, and control of successful and effective radiant cooling and heating systems. This has created a situation where radiant systems are being designed, installed, and operated with only limited guidance and often inappropriate tools to assist the designer and building operator. To achieve the significant reductions in building energy use proposed by CPUC’s Energy Efficiency Strategic Plan that all new non-residential buildings be zero-net-energy by 2030, it is critical that new technologies that will play a major role in reaching this goal be applied in an effective manner.

Research Approach

The technical approach will include a combination of fundamental full-scale laboratory experiments, whole-building energy simulations, development of simplified models for radiant system controls, validation of these new methods in field studies, occupant satisfaction surveys, and an update to Title-24 for radiant systems. Research tasks include:

Laboratory tests: In collaboration with Price Industries, we will conduct full-scale laboratory experiments to understand the behavior of radiant slab systems, for example, to determine cooling loads, cooling capacity, and system sizing issues, and to investigate the impacts of acoustical ceiling systems. Additional tests to be conducted at FLEXLAB will take into account solar gains and evaluate optimized control strategies.

Simplified design and control tools: Results from the lab testing will provide a realistic range of radiant system configurations. We use this information to create a simplified design and operation tool for radiant slab systems, and we will implement this via a web-based tool.

Field studies: Conduct detailed field studies in three field studies of radiant slab buildings, to include occupant satisfaction surveys, system monitoring, analysis of system and energy performance, and testing and demonstrating optimized control approaches. CBE's industry partners at Viega identified the ARTIC project (image right) as a potential field study site. Delta Products has also agreed to provide their new headquarters building in Fremont, California, as one of the field study sites.

Energy analysis, cost assessment, and occupant surveys: CBE will identify approximately 50 buildings having radiant systems, and gather and analyze data for energy performance, cost, and occupant satisfaction. This work will provide industry with reliable comparisons of radiant system performance in comparison to other buildings.

Codes and standards: Provide updates to the Title 24 Alternative Calculation Method Reference Manual, to enable improved modeling capabilities of radiant systems. Participate on related ASHRAE Standards and Technical Committees to provide new information and guidance based on the results of the above mentioned tasks.

Project Team

CBE faculty and staff will lead the project, with support from Taylor Engineering, New Buildings Institute, TRC, and Price Industries.


Higgins, C. and K. Carbonnier. 2017. Energy Performance of Commercial Buildings with Radiant Heating and Cooling. Internal report. June.

Paliaga, G., F. Farahmand, P. Raftery, and J. Woolley. 2017. TABS Radiant Cooling Design & Control in North America: Results from Expert Interviews. Internal report. June.

ARTICThe recently completed Anaheim Regional Transportation Intermodal Center (ARTIC), designed by CBE partners HOK and BuroHappold, uses an innovative radiant system.

SMUD HQDelta Products Headquarters, in Fremont, CA, is a CBE field study site.