## 1 Introduction  
The industrial sector must reduce its energy demand as it is responsible for almost 40% of global final energy consumption [1], yet considerable increases are anticipated. The US Energy Information Administration (EIA) project that the industrial sector's energy use will grow nearly twice as fast as any other end-use sector between 2021 and 2050 [2]. The industrial sector therefore faces a significant challenge to attain ambitious sustainability targets, such as doubling the global rate of energy efficiency improvement [3]. In a competitive global market, ensuring sustainability targets are met, while simultaneously driving growth, is a key significant challenge. In Europe, the European Union (EU) outlined the need to protect, conserve and enhance the EU's natural capital, transition to climate neutrality, while also reducing waste in the European Green Deal [4]. The EU recognized the severity of the sustainability challenges and the need for a strategic change, hence the \"Twin Transition\" was proposed [5]. To ensure Europe achieves sustainability goals to become greener, but also increase competitive advantage, the EU proposed digitalization as a key enabler for both goals. Information and Communications Technology can enable a 20% reduction of global CO\({}_{2}\) emissions by 2030, which could provide the necessary environmental protection while avoiding a trade-off with economic prosperity [6]. The International Renewable Energy Agency (IRENA) estimates that if manufacturing companies adopted the best available technologies, then the consumption globally would reduce by about a quarter [7]. The industrial sector is comprised of many different subsectors such as manufacturing, pharmaceuticals, food, construction and oil and gas. While the constituent assets and processes that account for the energy consumption in these subsectors will differ, indoor facilities have a common, energy intensive requirement to provide ventilated working environments. Heating, Ventilation and Air Conditioning (HVAC) systems, which provide fresh air as well as heating and cooling needs, consume about 50% of building energy consumption on average [8]. In an industrial facility, this figure reduces to about 40% on average [9], while 34% of hi-tech facilities managers say HVAC is their site's biggest energy cost [10]. There is high potential for energy savings in HVAC systems as they are self-correcting in nature, which facilitates the occurrence of unnoticed faults that may account for up to 20% of the energy consumed by these systems [11]. Monetarily, [PERSON] [12] estimated that common faults such as duct leakage, dampers not working properly and valve leakage cost 2.9, 0.5 and 0.1 Sbillion/year, respectively, in commercial buildings, based on the findings by [PERSON] et al. [11]. HVAC systems therefore need to be well maintained, but maintenance costs, time for repair, and replacement of components that have not reached the end of their useful life must be balanced with the potential energy savings. As noted by [PERSON] et al. [13], \"equipment maintenance can exceed 30% of total operating costs, or between 60 and 75% of equipment lifecycle cost [14]\". Therefore, selecting an appropriate maintenance strategy is critical to be cost effective. Traditional maintenance practices are reactive in nature with a \"fail and fix\" philosophy [15]. These approaches are known as reactive or corrective maintenance whereby the main strength is reduced maintenance costs [16]. However, the increased time interval between maintenance activities could lead to hidden costs such as suboptimal operation, while also increasing the likelihood of costly downtime [16]. An alternative approach would be an evolution from reactive maintenance to proactive \"predict-and-prevent\" maintenance [15].