Abstract

Based on recent investigations on building envelope with phase change materials from all over the world, we select the key scientific and technical issues including the thermal design methods, climatic and seasonal suitability and application, etc. The chapter mainly contains four parts: how to design building envelope with phase change materials, how to deal with issues on climatic and seasonal suitability of the technology, how to improve thermal performance of phase change materials applied in building envelope, and what is the application mode. The thermal design principle and a simple calculation method of building envelope with phase change materials are proposed by experiments. Thermal comfort pertaining to ASHRAE Standard 55 under different conditions is investigated, and an approach to estimate favorable climatic characteristics for building envelope with phase change materials is established. To exert the phase change materials applied in building envelope effectively, thermal transfer enhancement methods and application are also provided in the chapter. The chapter can be helpful for the development of building energy efficiency and the goal of zero and net zero energy.

Keywords: building envelope, phase change materials, thermal design, climatic and seasonal suitability, application

## 1. Introduction

Building energy saving is essential to overall energy conservation from different sectors [1]. To build a comfortable indoor thermal environment, the energy consumption of air conditioning is increasing rapidly, which has negative impacts on sustainable development. Passive low-energy buildings are developed to solve the problem [2]. Improving thermal performance of building envelope is an effective approach to achieve a stable indoor thermal environment and reduce building energy consumption [3]. There are two main ways for the improvement of building envelope thermal performance. One is to reduce heat transfer coefficient (U-value) then decrease the heat flux of building envelope. Another is to increase thermal inertia of buildings to enhance the resistance to the changing of outdoor thermal environment [4, 5], especially in climate conditions with large daily temperature range, where remarkable energy efficiency performance could be achieved by improving building thermal stability [6, 7]. Adopting heavy structure (such as earth brick) is a traditional method for the improvement of building thermal stability [8]. However, the traditional approach is not suitable for achievement of satisfying

influence, the wallboards of test cell are made by 100 mm expandable polystyrene (EPS) panels which can be considered as adiabatic. In the experiments, PCM-based lightweight wallboard is adopted to replace one of EPS panel (see Figure 2). The macro-encapsulated PCM panels are employed in the experiments. The encapsulated PCMs are CaCl2�6H2O, whose phase change temperature is 25–27°C. In melt-

The experimental wallboard named PCM-based lightweight wallboard is put forward. The wallboard is made by 20 mm PCM layer and 30 mm insulation material layer. The wallboard improves its thermal storage capacity obviously by utilizing PCMs while sacrificing a fraction of insulation performance. The PCMbased lightweight wallboard is divided into PCM part and insulation part to distin-

> <sup>r</sup><sup>A</sup> <sup>¼</sup> <sup>A</sup>PCM AALL

where APCM is the area of PCM and AALL is the area of the wallboard. The wallboards with four r<sup>A</sup> are compared in experiments: 0, 21.6, 43.3, and 65%. The reference group (r<sup>A</sup> = 0%) is performed firstly to benchmark the PCMbased lightweight wallboard experiments. Figure 3 shows the temperature curves of reference group during harmonic temperature changing process. Comparing the

, and in solidification process the latent

(1)

ing process, the latent heat is 122.3 kJ�kg�<sup>1</sup>

Building Envelope with Phase Change Materials DOI: http://dx.doi.org/10.5772/intechopen.85012

guish whether there are PCMs in the horizontal direction.

r<sup>A</sup> is defined as the ratio of PCM part area to wallboard area:

.

heat is 116.9 kJ�kg�<sup>1</sup>

Figure 2.

Figure 3.

13

PCM-based lightweight wallboard.

Temperature under harmonic temperature fluctuation.

#### Figure 1. Principle of PCM-based envelope.

thermal storage performance in lightweight structures widely developing in recent years. Due to large thermal capacity, phase change materials (PCMs) are ideal thermal storage materials to be integrated with building envelope [9]. As shown in Figure 1, building envelope integrated with PCMs can improve thermal inertia of lightweight structures and further stabilize indoor thermal environment [10]. Therefore, the thermal performance of PCM-based envelope has attracted more attention in recent years.
