Optimal supply air temperature with respect to energy use in a variable air volume system

Research output: Contribution to journalArticle


In a variable air volume (VAV) system with 100% outdoor air, the cooling need in the building is satisfied with a certain air flow at a certain supply air temperature. To minimize the system energy use, an optimal supply air temperature can be set dependent on the load, specific fan power (SFP), chiller coefficient of performance, outdoor temperature and the outdoor relative humidity. The theory for an optimal supply air temperature is presented and the heating, ventilation and air-conditioning (HVAC) energy use is calculated depending on supply air temperature control strategy, average U-value of the building envelope and two outdoor climates. The analyses show that controlling the supply air temperature optimally results in a significantly lower HVAC energy use than with a constant supply air temperature. The optimal average U-value of the building envelope is in practise mostly zero. (C) 2003 Elsevier B.V. All rights reserved.


Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Building Technologies


  • supply air temperature, heating, ventilation and air-conditioning, variable air volume system
Original languageEnglish
Pages (from-to)205-218
JournalEnergy and Buildings
Issue number3
Publication statusPublished - 2004
Publication categoryResearch