Performance analysis of an integrated UFAD and radiant hydronic slab system

Paul Raftery, Kwang Ho Lee, Tom Webster, Fred Bauman

Research output: Contribution to journalArticlepeer-review

31 Citations (Scopus)


In this paper, an EnergyPlus model was used to simulate the operation of a novel integrated HVAC system. This system combines an underfloor air distribution system with a cooled radiant ceiling slab. A cooling tower supplies water to pre-cool the structural slabs during the night and early morning period. The paper compares the performance of this system to both a typical overhead system and a typical UFAD system in the cooling season for the Sacramento, California climate. When compared to the overhead system, the integrated UFAD/Radiant system shows a 22-23% reduction in total energy consumption during the peak cooling months (June to August) and a 31% reduction in peak hourly electricity demand. When compared to the UFAD system, these reductions are 21-22% and 24% respectively. An investigation of the simulation results showed that the integrated UFAD/Radiant system also improves occupant thermal comfort and reduces thermal decay issues in the underfloor plenum.

Original languageEnglish
Pages (from-to)250-257
Number of pages8
JournalApplied Energy
Issue number1
Publication statusPublished - 2012 Feb
Externally publishedYes

Bibliographical note

Funding Information:
This work was primarily funded by the Irish Research Council for Science Engineering and Technology (IRCSET) EMBARK initiative and the Fulbright Commission. This work was partially supported by the California Energy Commission (CEC) Public Interest Energy Research (PIER) Buildings Program and the Center for the Built Environment, UC Berkeley. Many thanks to Stefano Schiavon of the Center for the Built Environment, UC Berkeley and Allan Daly of Taylor Engineering, Alameda, CA for their assistance and for the time they have spent working on the models and the interface used in this investigation.


  • Energy performance
  • EnergyPlus
  • Hydronic slab
  • Radiant cooling
  • Thermally activated building systems
  • Underfloor air distribution

ASJC Scopus subject areas

  • Building and Construction
  • General Energy
  • Mechanical Engineering
  • Management, Monitoring, Policy and Law


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