Research

Thermal comfort in buildings using radiant vs. all-air systems: A critical literature review

Stefano Schiavon, Assistant Professor of Architecture

Team

Caroline Karmann, Ph.D Candidate, Stefano Schiavon, Ph.D and Fred Bauman, PE

Partners

California Energy Commission Electric Program Investment Charge and the Center for the Built Environment

Project Description

A team of researchers at the Center for the Built Environment has conducted a critical literature review to determine if radiant heating and cooling systems provide better, equal or lower thermal comfort than all-air systems in buildings. The review was conducted by Caroline Karmann, Ph.D Candidate, Stefano Schiavon, Ph.D and Fred Bauman, PE. The research team identified results from eight conclusive studies out of a total of seventy-three studies reviewed. Five studies could not establish a thermal comfort preference between all-air and radiant systems and three studies showed a preference for radiant systems. Overall, the team determined that a solid answer could not be given. 

Abstract: Hydronic radiant heating and cooling systems are considered an energy efficient technology to condition buildings. We performed a literature review to assess if radiant systems could provide better, equal or lower thermal comfort than all-air systems. We included only peer-reviewed articles and articles published in proceedings of scientific conferences. The publications we found have been classified based on the following research methods: (1) building performance simulation (BPS), (2) physical measurements (in laboratory test chambers and in buildings) and (3) human subject testing/occupant based surveys. This review identified eight conclusive studies: five studies that could not establish a thermal comfort preference between all-air and radiant systems and three studies showing a preference for radiant systems. Very few studies were based on occupant feedback in real buildings suggesting a significant research need. Overall, we found that a limited number of studies are available and therefore a solid answer cannot be given. Nevertheless, there is suggestive evidence that radiant systems may provide equal or better comfort than all-air systems.

These studies used multiple methods to demonstrate their findings and, in addition, several types of all-air and radiant systems were tested. The two systems performed similarly when compared based on building energy simulation, laboratory studies and and human subject testing in laboratory conditions. Radiant cooling ceiling panels showed better results than all-air systems based on laboratory studies and occupant responses in a building. A side-by-side field comparison between an all-air system and TABS with DOAS that was based on occupant survey responses showed increased satisfaction with thermal comfort for the radiant system. All these studies were fully (or mainly) about cooling applications (only one heating variant was referenced.

Publication: Karmann C, Schiavon S, Bauman F.  Thermal comfort in buildings using radiant vs. all-air systems: A critical literature review. Building and Environment. Volume 111, January 2017, Pages 123–131