Energy & Buildings 168 (2018) 1–8 Contents lists available at ScienceDirect Energy & Buildings journal homepage: www.elsevier.com/locate/enbuild Dynamic thermal properties of building components: Hot box experimental assessment under different solicitations Giorgio Baldinelli a,∗ , Francesco Bianchi a , Agnieszka A. Lechowska b , Jacek A. Schnotale b a Department of Engineering, University of Perugia, Via Duranti, 67, Perugia 06125, Italy b Department of Environmental Engineering, Cracow University of Technology, ul. Warszawska 24, Cracow 31-155, Poland a r t i c l e i n f o Article history: Received 9 September 2017 Revised 16 February 2018 Accepted 1 March 2018 Available online 10 March 2018 Keywords: Dynamic thermal properties Heat transfer matrix Time shift Hot box Harmonic solicitations a b s t r a c t The envelope thermal behaviour in dynamic conditions is becoming essential to assess the whole year energy performance of buildings. International Standards describe in detail the theoretical approach, but few examples of experimental analyses and procedures exist to determine the performance of materials and components in unsteady-state conditions. The work is aimed at filling this vacancy, describing a modification of hot box devices, which are generally designed for stationary measurements, but they could be successfully used also for time-dependent investigations. Two different methods are proposed: a hot box system where one-day period sinusoidal solicitations in terms of temperature and heat flow are imposed, and another type of boundary condition, with a faster impulsive thermal driving force. The former showed a good agreement with the expected theoretical results; the latter proved also suitable but suffered a lower accuracy, being characterised in turn by a significant reduction of the measurement time. It is also showed that hot boxes allow also more detailed investigations, such as infrared thermography imaging, to better analyse the thermal performance of the tested samples. © 2018 Elsevier B.V. All rights reserved. 1. Introduction The dynamic behaviour of the building envelope is gaining in- creasing importance, as the analysis of buildings energy perfor- mance needs to be more and more accurate, extended to all sea- sons, summer included, when the steady-state conditions hypoth- esis (acceptable in winter time for moderate and cold regions) has to be abandoned. Many well-established theoretical approaches exist: the Stan- dard EN ISO 13786 [1] proposes a procedure aimed at finding the dynamic thermal response when homogenous layers are sub- jected to periodic sinusoidal solicitations. Besides, other solutions are available for the analysis in transient non sinusoidal conditions, such as the response factor methods [2,3]. The geometrical (thickness d) and thermophysical parameters (thermal conductivity λ, density ρ and specific heat capacity c) needed for the theoretical analysis are rarely available for all ma- terials and often they present low levels of accuracy. Therefore, the laboratory direct experimental assessment of the dynamic be- haviour of multilayer components appears as an appealing and ef- fective alternative, and it constitutes the main objective of this work. ∗ Corresponding author. E-mail address: giorgio.baldinelli@unipg.it (G. Baldinelli). In more detail, the possibility of using hot box devices to as- sess experimentally the dynamic properties of materials has been explored, following the method indicated in the EN ISO 13786 [1], with two different approaches: 1) imposing sinusoidal excitations exactly as indicated in the Stan- dard; 2) supplying an impulsive, brief solicitation, and extracting the same harmonics of the previous method with the Fast Fourier Transform technique. This approach differs from previous works of most of re- searchers, who moved adapting the steady-state regime measure- ment setups to the variable conditions. For instance, the modifi- cation of the guarded hot plate technique [4] for unsteady-state analysis appeared a solution hard to implement, because of the di- mension limits of the samples, the difficulty on including air gaps, and the unfeasibility of incorporating laminar coefficients on the samples thermal analysis. On the other hand, the hot box devices [5] earned a relevant success, as they overcome the previous men- tioned obstacles, despite the higher complexity of the apparatus and the long time necessary for the measurements. At the be- ginning of the 70 ′ s, Bondi et al. [6] conducted a series of exper- iments in a forerunner hot box setup, built with an internal room bounded by two identical wall specimens, facing in turn two ex- ternal rooms at the same temperature conditions. They described https://doi.org/10.1016/j.enbuild.2018.03.001 0378-7788/© 2018 Elsevier B.V. All rights reserved.