# The Interplay between Air Quality and Energy Efficiency in Museums, a Review
## 1 Introduction  
Climate change is a reality in today's world [1]. It is strongly dependent on the energy production by fossil fuels and the energy consumption by diverse human activities, both of which contribute to CO\({}_{2}\) and other greenhouse gases emissions. Climate change and occasionally erratic power supply conditions sped up the political decisions to reduce energy demand and to produce renewable energy, i.e., energy derived from natural sources that are replenished at a faster rate than they are consumed. Furthermore, energy efficiency (EEF) is strongly pursued in an effort to use less energy to achieve the same task or product. The built environment is critical to achieving energy efficiency and other environmental objectives. Homes and buildings that are energy efficient use less energy to achieve comfortable living and working conditions. The Directive 2012/27/EU and the 2018 amending Directive on Energy Efficiency in the EU seek to save energy while also promoting good indoor air quality and comfort. However, they do not specify how to achieve both the goals of energy savings and satisfactory indoor environmental quality. The legislation governing indoor air quality (IAQ), in particular, is fragmented. The amount of particulate matter (PM), airborne inorganic, organic, and biological particles, such as SARS-CoV-2, fungi, bacteria, and gaseous pollutants, present in the indoorair is defined as indoor air quality (IAQ). Indoor environmental quality (IEQ) includes not only air pollution within a building, but also lighting, thermal conditions, ergonomics, and other conditions that may be harmful to occupants. In other words, all the conditions within the building that allow it to be used for its intended purpose. Aside from human health and comfort, the IEQ has an impact on the materials used to create works of art. Since the 1970s, numerous studies have been conducted to investigate the deterioration of valuable objects housed in museums, churches, mosques, temples, and other historical buildings, as well as private collections [2; 3; 4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19]. Climate change influences outdoor air pollution and causes severe and frequent weather extremes [20]. This changes the indoor environment, affects IEQ and interferes with energy consumption [21; 22], hence undermining climate change mitigation efforts [23]. The COVID-19 pandemic underscored the significance of maintaining proper IAQ control. Apart from the well-established fact that IAQ affects productivity and wellbeing, this control or lack of it has emerged as a key factor in the transmission of infectious diseases. Numerous studies support the notion that in order to achieve good IAQ, particularly in public buildings such as schools, hospitals, and museums, more energy expenditures are required for air filtration, ventilation, etc. EEF is thought to be inversely proportional to good IAQ [24; 25]. In crowded buildings, balancing energy efficiency with good indoor air quality is even more difficult. Museums preserve the cultural heritage of our planet and promote culture and knowledge. They are popular tourist destinations all over the world. According to UNESCO, the number of museums worldwide has increased from 22,000 in 1975 to 95,000 today [26]. These structures necessitate a large amount of energy for heating, cooling, and lighting, as well as good air quality. IEQ management is critical for the preservation of artworks as well as for the health of both staff and visitors. The world's cultural heritage is facing new challenges as a result of climate change and the need to conserve energy [27]. People in charge of the world's collections understand that displaying or storing them in appropriate environmental conditions prevents deterioration more effectively than restoring them. Air temperature and relative humidity have historically been the primary conservation concerns in buildings that house works of art, whether historical or modern.