## 1 Introduction  
After the COVID-19 pandemic, in 2021, the building sector returned to pre-pandemic levels not only in most major economies, but also in more emerging economies thus increasing their use of fossil fuel gases in the process [1]. Population growth led to new constructions and an increase in the demand of resources [2]. As a result, energy consumption rose by 4%, its largest increase in 10 years [3]. In this sense, the Sustainable Development Goals (SDG) have been set in place to try and reduce this problem within the building sector while improving people's quality of life through SDG 7, 9, and 12 [4]. Buildings are responsible for 40% of the world's energy consumption and related CO\({}_{2}\) emissions, which is one of the main factors to be considered in climate change [5]. This consumption includes both operational and embodied energy. Despite industrialisation modifying building construction processes, there is still a lack of implementation [6]. Traditional materials like bricks and concrete are still being largely used due to their low price and good mechanical performance. However, these materials need vast amounts of energy to be produced and have low thermal conductivity properties [7]. Therefore, it is necessary to design energy-efficient buildings that use more sustainable materials and consider the integration of renewable energies sources. Traditional construction methods must be replaced with precast materials and industrialised buildings to achieve the aim of minimising environmental impact. Operational energy consumption is mostly produced by the air conditioning in buildings, especially in housing and office buildings [8]. This is due to a deficiency in the performance of the building materials and their main properties. With this context, plaster-based materials have been raised as a major solution and source of possibilities to improve the hygroscopic conditions inside buildings, as well as reduce operational energy consumption [9]. Plaster-based materials are versatile, cheap, and have a good workability, all of which make them suitable to work with. This fact has led to the development of several experimental studies aimed at improving their main properties, while maintaining the characteristics that make it suitable. To reduce this material's thermal conductivity, the literature shows two schools of thought. On the one hand, matrix modification which pertains to making the material foamed or lighter; on the other hand, through differently shaped additions. Foaming is achieved using chemical additions. A study presented by [PERSON] et al. used a mixture of natural solutions to foam the final material [10]. Zaragoza-Benzal dissolved extruded polystyrene (XPS) and expanded polystyrene (EPS) to lighten their final material [11]. Meanwhile, [PERSON] et al. used aluminium sulphate and sodium bicarbonate as gas-producing additives to activate the reaction [12]. These reactions produce bubbles while setting, making the final material more porous. Despite this great advantage, all these products become flammable following this process and their use in buildings is not entirely safe. The use of synthetic polymers as a partial replacement in the plaster matrix also achieves a lighter material as well as reduces its thermal conductivity. Most studied materials include EPS and XPS. Several studies have used grain-sized polystyrene as a lightener [13; 14; 15; 16]. The main benefits are the apparent density and reduction in thermal conductivity, although it also produces a considerable decrease in mechanical strength. Because of this, fibres are the other most studied shaped addition in plaster-based materials. Its apparent density is slightly bigger than in foamed plasters, but the mechanical properties are less affected. Natural fibres, such as palm fibre, Posidonia, cellulose, and wood, have been studied and shown to result in better flexural strength behaviour and a reduction in thermal conductivity [17; 18; 19; 20].