Contents lists available at ScienceDirect Engineering Failure Analysis journal homepage: www.elsevier.com/locate/engfailanal Designing insulation filled masonry blocks against hygrothermal deterioration Balázs Nagy ⁎ Budapest University of Technology and Economics, Faculty of Civil Engineering, Department of Construction Materials and Technologies, Műegyetem rkp. 3, 1111 Budapest, Hungary ARTICLE INFO Keywords: Heat and moisture transfer Dynamic hygrothermal simulation Freeze-thaw Thermal conductivity Insulation filled masonry ABSTRACT Due to increasingly stringent requirements in building energy performance, further development of fired clay masonry blocks are essential nowadays for the manufacturers. One of the possible directions for improving thermal performance of the masonry blocks is to fill them with in- sulating materials. The currently developed bricks are most commonly containing mineral wool thermal insulation filler. The main criteria for manufacturers to develop their products are thermal performance and manufacturability, which leads to unsolved hygrothermal questions. While the filler materials have low thermal conductivities, they may deteriorate in high humidity environment and due to freeze-thaw cycles. The aim of this research is to test existing filled building blocks, to prevent hygrothermal deterioration. The study compares one-dimensional monthly based steady state Glaser method with steady state two-dimensional hygrothermal si- mulations and dynamic multi-dimensional conjugated heat and moisture transfer simulations. The calculations were made considering Central European Budapest climate. Hygrothermal material properties were measured in laboratory. After the calculations, results show that ef- fective thermal transmittance, maximum freezing depth from the external surface of the plastered masonry blocks and the number of freeze-thaw cycles during a year vary depending on the fa- cade's orientation. The possible freezing zone can reach one third of the masonry block from the external side, and affect the thermal performance of the bricks. The outermost insulation layers of the masonry blocks therefore must selected to bear freeze-thaw cycles and high humidity because of protection aspects. The new aspects of this study can be used to extend the application limits of insulation filled masonry blocks and design these type of masonry blocks against hygrothermal deteroriation. 1. Introduction Nowadays, building energy performance regulations are more and more rigorous, and traditional masonry wall constructions usually need additional external thermal insulation, if the building block is not extremely thick and has well optimized internal structure. Fired clay masonry block manufacturers addressed the problem, that people rather buy smaller blocks and insulate them from the external side, than buy thicker, heavier and more expensive bricks. Therefore, manufacturers started to produce masonry block filled with thermal insulation to increase the thermal resistance of the bricks and sell insulation together with the masonry blocks. Insulation filled blocks however, due to ensure manufacturability, have simple rectangular internal shapes of the filled holes. https://doi.org/10.1016/j.engfailanal.2019.05.005 Received 27 November 2018; Received in revised form 15 April 2019; Accepted 2 May 2019 ⁎ Corresponding author. E-mail address: nagy.balazs@epito.bme.hu. Engineering Failure Analysis 103 (2019) 144–157 Available online 04 May 2019 1350-6307/ © 2019 Elsevier Ltd. All rights reserved. T