Experimental thermal characterization of a Mediterranean residential building with PCM gypsum board walls I. Mandilaras, M. Stamatiadou, D. Katsourinis * , G. Zannis, M. Founti National Technical University of Athens, School of Mechanical Engineering, Lab. of Heterogeneous Mixtures and Combustion Systems, Heroon Polytechniou 9, Athens, Greece article info Article history: Received 12 September 2012 Received in revised form 11 December 2012 Accepted 14 December 2012 Keywords: Building monitoring Phase change materials Thermal energy storage Energy efficiency abstract A two-storey typical family house was built in the mid-western part of Greece, comprising a load bearing steel skeleton and dry wall systems. Its walls consist of multiple layers of insulation materials and gypsum plasterboard panels containing Phase Change Materials (PCMs) for thermal energy storage purposes. A detailed matrix of sensors was installed in different locations of all external walls of the house, as well as indoors, in order to provide detailed temperature measurements and thus lead to a thorough depiction of the house’s thermal behaviour. In this work, experimental data obtained during the first year of monitoring (2011) are presented. Throughout this particular monitoring period the house purposely remained closed, unoccupied and no energy systems were installed. Hence the presented analysis focuses on the thermal characterization of the house’s walling system. Average monthly temperature, decrement factor and time lag values are presented for each roomewall and are discussed with respect to their orientation and exposure to the external weather conditions. Furthermore, measurements conducted on different layers of the living room’s east wall aim to examine the influence of PCMs in the wall’s thermal response. It is shown that within the adopted conditions (unoccupied house/no energy systems), the thermal mass of the walling system is enhanced during late spring, early summer and autumn, due to the PCM implementation, resulting also in a decrease of the decrement factor by a further 30e40% and an increase on the time lag of approximately 100 min. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Now-a-days, the need for more energy-efficient and sustainable buildings becomes more and more pronounced due to changing living habits (working from home) accompanied by abrupt market (e.g. fuel costs), economic and environmental changes. New building materials are needed, with improved and controllable thermal properties, capable of reducing heating and cooling energy demands, ensuring thermal comfort of the occupants. Lightweight buildings are inherently characterized by low thermal inertia contrary to massive construction. It has been shown that by incorporating Phase Change Materials (PCM) into lightweight building materials, latent heat storage can compensate for their small heat storage capacity [1]. The use of Phase Change Materials (PCMs) for energy storage and increase of thermal mass has been studied since the 1940s [2,3]. However, their usage in buildings has gained interest during the last three decades, due to reductions in their cost [4]. PCMs are characterized by a specific phase change (melting and solidifying) occurring at a temperature value or range due to latent heat. When these materials are implemented in building components (e.g. walls), they attain an improved ability to effectively store the solar energy that enters a room in the daytime, leading to the establishment of cooler conditions in internal spaces. Conversely, when temperatures decrease and become lower than the PCM’s characteristic melting point (usually at night), the material solid- ifies and the previously absorbed heat (latent heat) is released, supporting the maintenance of higher indoor temperatures. Numerous review papers can be found in the literature, providing a detailed analysis of PCMs main characteristics, focussing on material properties and assessing their applications and possible benefits [5e8]. Recently, Zhou et al. [9] summarized research studies focussing on thermal energy storage with PCMs on building applications and with respect to evaluating their potential. During the last decade, the majority of research on PCM application in buildings was limited to small scale experiments (e.g. investigation of a sample or a wall) [1,10e12]. However recently, research has been also directed to full scale real test cases (cells or rooms with one or more PCM walls). Towards this direction, experimental work and/or numerical predictions have * Corresponding author. Tel.: þ30 210 7721218; fax: þ30 210 7723527. E-mail address: dimkats@central.ntua.gr (D. Katsourinis). Contents lists available at SciVerse ScienceDirect Building and Environment journal homepage: www.elsevier.com/locate/buildenv 0360-1323/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.buildenv.2012.12.007 Building and Environment 61 (2013) 93e103