# Improvement of Buildings' Air Quality and Energy Consumption Using Air Purifying Paints
## 1 Introduction
Nevertheless, apart from thermal comfort, there are other important aspects. To overcome the above drawbacks, the application of passive removal materials (PRMs) was proposed for indoor air quality improvement [7]. These materials are able to reduce indoor air pollutants without significant energy demands and by-product formation. The type of pollutants, environmental and operational factors, and characteristics of PRMs play significant roles in the effectiveness of PRMs. The Energy Performance of Buildings Directive (EPBD) (Directive 2010/31/EU) includes articles on the general framework for a methodology to calculate the integrated energy performance of buildings and standards for their energy performance, indirectly impacting ventilation rates and, consequently, indoor air quality [8]. Other regulations refer to product construction, like Regulation (EU) No. 305/2011, which sets out conditions for the marketing of construction products, including requirements for the emission of harmful substances from construction materials [9]. Focused around energy conservation, European norms emphasize the commitment to reduce energy consumption in buildings. Predominantly, the HVAC systems, which play a prime role in determining energy usage, come under the spotlight. These regulations heavily favor the employment of energy-efficient technologies and best practices--such as efficient thermal insulation, utilization of natural ventilation, heat recovery systems, innovative building materials, and more--that contribute to a decrease in overall energy consumption. The issue in our case is not only to correlate energy consumption to the ventilation rate but also to achieve the same level of pollutant reduction as if we used the photocatalytic paint. So, the problem to solve gets more complicated as three parameters need to be balanced and evaluated: air quality, energy consumption, and ventilation. Beyond the advantages of photocatalytic interventions in a building in terms of IAQ improvement and energy savings, a number of limitations have been reported in the literature. One of the limitations of TiO\({}_{2}\)-based photocatalytic paints is their low adsorption capacities [10]. To counterbalance this drawback, intense efforts have been made to load TiO\({}_{2}\) on an absorbent supporting medium, e.g., a graphene structure, activated carbon, or zeolite, to improve TiO\({}_{2}\) effectiveness [11; 12; 13]. Overall, the efficiency is increased by the modification of the photocatalyst supporting medium. It is attributed to (a) the rise in the reaction surface area of the photocatalytic material, (b) the availability of the photocatalyst within the medium, and (c) the increased contact time between the gas and the photocatalyst. Furthermore, various TiO\({}_{2}\) photocatalysts have been modified in order to enhance their photocatalytic capacity [14; 15; 16; 17; 18]. In building materials, attempts have been made in changing surface morphology to obtain the desired performance of photocatalytic materials mentioned above. [PERSON] et al. (2017) improved standard paints' remediation capacity through the management of adsorption properties by changing siliceous filler to ones having higher porosity and specific surface area [19]. Furthermore, it is well known that in the presence of UV radiation, photocatalytic paints emit VOCs themselves [1; 20; 21; 22; 23]. More specifically, the active radical species (OH and O\({}^{2-}\)) generated on the catalyst surface under UV irradiation react with the organic binder molecules that are present in the paint matrix to produce and emit VOCs. The latter consist of a significant shortcoming for the application of photocatalytic paints that contain organic solvents or organic binders to a certain degree. On the other hand, the presence of organic binders in paints is structurally important as it keeps the pigments stable after the paint dries.