The response of clay plaster to temperature and RH sinusoidal variations

Abstract

Hygroscopic finishing materials can be used to moderate indoor humidity levels; they have the capacity to adsorb and release moisture from and to the surrounding air, depending on the indoor relative humidity levels. To determine the moisture buffering properties of materials several protocols have been introduced. However, testing procedures are based on a time-response method, where humidity variations are under a square wave function and temperature remains constant. Therefore, the ability of these methods to simulate material behaviour under real conditions, where cyclical humidity variations are more gradual, and temperature is variable, has been called into question. The aim of this study is to perform a standard moisture buffering test, by substituting the step-variation method, with a sinusoidal humidity function at different temperatures. Clay has been used to perform the tests in a climatic chamber, where a small increase of relative humidity have been set, in order to obtain a quasi-sinusoidal curve. The relative humidity variation are limited by low humidity (33% RH) and high humidity (75% RH) and temperature variation between 18 °C and 28 °C. Materials tested present a lag in the response to the peak relative humidity to peak mass gain, which suggests an alternative way to consider the rate of sorption and the moisture storage function. The significance of the paper is to develop a laboratory test that can be more readily compared with the behaviour real buildings, which operate under more of a sine waveform

Development of Clay-Composite Plasters Integrating Industrial Waste

“…In addition to the great advantage of reduced environmental impact, buildings made from raw-clay-based materials have several benefits in terms of indoor air quality and, implicitly, the health of the population: water vapor permeability, the ability to regulate indoor air humidity, and high storage/heat release capacity, thus contributing to thermal comfort, increasing indoor air quality and energy efficiency. However, the difficulties these materials present are primarily in terms of mechanical strength and resistance to the action of climatic factors being lower compared to concrete buildings, as well as a reduced degree of compatibility with classic finishing materials available on the market [2][3][4][5][6][7][8][9][10][11][12][13]. Consequently, there is a need to develop plaster and finish materials that are compatible with the primary materials used for traditional construction (natural stone, burnt ceramic brick, and masonry elements based on raw clay, wood, and wood-based or other lignocellulosic materials).…”

“…Indoor finishing materials play a significant role in shaping the indoor climate due to their moisture-buffering capabilities. These capabilities arise from the sorption and diffusion properties of the materials, which help maintain a balanced indoor environment [2][3][4][5]. The inherent thermal properties of clay building elements and finishes contribute to their capacity to effectively regulate indoor temperature.…”