Integrating active thermal mass strategies with HVAC systems in officebuildings: development of a concept design tool

Thermal mass can be used in buildings toreduce the need for and dependence onmechanical heating and cooling systems whilstmaintaining environmental comfort. Activethermal mass strategies further enhance theperformance of thermal mass throughintegration with the Heating, Ventilation andAir Conditioning (HVAC) systems. For thedesign of new buildings to include activethermal mass strategies, experience fromoperational projects and design guidelines arenormally used by engineers. However, dynamicthernial modelling is required in most cases toaccurately determine the performance of itsintegration with the environmental systems ofthe building. Design decisions made in thepreliminary stages of the design of a buildingoften determine its final thermal characteristics.At this stage, reasons for not integrating activethernial mass strategies include the lack oflcnowledge about the performance of previousbuildings and the time and resources required to carry out detailed modelling.This paper outlines a simplified design toolthat can be used at the concept design stages ofa typical office building to determine thebenefits of integrating an active thermal massstrategy. This was developed by carrying outsimulations using a dynamic thermal modelwhich was calibrated- by measurements inoperational buildings with active thermal massin the UK. Four active thermal mass strategiesare considered (a) hollow core slabs (b) earthto-air heat exchanger (c) floor void with massand (d) thermal labyrinth in addition to a standard office with no active thermal mass. Key design parameters were identified for each system and parametric analysis was carried out to determine the resulting environmentalconditions and energy consumption in the office.The tool has an easy-to-use interface whichallows direct comparison of the different activethermal mass strategies together with the effectsof changing key design parameters. Results arepresented in terms of thermal comfort andenergy consuniption.