PREFACE This design guide is a revision of the REHVA Chilled Beam Application Guidebook@ which was published in 2004. ASHRAE and REHVA decided to collaborate on a revision of the guidebook and enlisted experts from both organizations to revise the document. This new guide is aimed at consulting engineers@ architects@ owners@ and contractors who are involved in the design@ operation@ and installation of active and passive beam systems. This book provides tools and guidance to design@ commission@ and operate active and passive beam systems to achieve a determined indoor climate. It also presents examples of active and passive beam calculations and selections. Online tools can be found at ashrae.org/beamcalc.