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


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

ASJC Scopus subject areas

  • Building and Construction
  • Energy(all)
  • Mechanical Engineering
  • Management, Monitoring, Policy and Law


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