Assessing the effectiveness for thermal mass in the building envelop

Abstract

The well known steady-state R-value traditionally used to measure energy performance of a building element does not reflect the dynamic thermal behaviour of the envelope, in particular it does not account for the possible benefits of thermal mass in reducing energy consumption for heating and/or cooling. This paper describes research to provide simple design guidance on the benefits of thermal mass. The paper is set in the context of building code requirements in Australia. The first part of the paper gives a brief history of understandings on the role of thermal mass in improving building performance. The so called m-Factor and similar techniques are described and examined. A new technique is proposed to show the effectiveness of thermally massive walls constructed of precast concrete sandwich panels. Using advanced thermal performance computer software data are derived to construct a Calculator that determines a Mass Enhanced R-value. This R-value can be used to demonstrate Building Code compliance.