Smart buildings : state of the art of smart systems for energy efficiency and assessment of their economic sustainability

Buildings contribute with values between 20% and 40% of the global energy consumption (Perez-Lombard et al, 2008), values that are higher than the consumption generated by the industry and transportation sectors. The growing in population and the migration of people to cities, especially in developing countries, have increased the necessity for building stock. For that reason, focusing on energy reduction in buildings through energy efficiency and smart systems is becoming an increasing priority. However, one of the main barriers to a faster implementation are the economic concerns. That is why we decided to make this project. To explain clearly what a Smart Building is and all the factors that affect energy consumption in one way or another, and how the implementation of different technologies and smart systems can generate positive financial results based, mainly, on the reduction in energy consumption. For this purpose, we first did research on the relation between green buildings, smart buildings, and energy efficiency. To realize how do they relate each other together with energy usage, and consequently putting deeper attention on the factors that have a direct impact on consumption. We also generated an economic model based on information concerning: energy consumption and distribution in different types of buildings, prices of energy, average savings due to the implementation of smart technologies, and prices of smart technologies. Obtaining indicators like Net Present Value, Payback Time (PT) and Internal Rate of Return (IRR). PT oscillated between 3 and 5 years, while the IRR between 24% and 54%. Values that would be optimistic when seen from a long-term point of view, without considering the additional benefits (markups in selling and renting rates) that it would bring. However, it is clear that in many companies, investments with PT higher than 2 years are not attractive, especially when pressure from shareholders is applied. Another important aspect to highlight is that the model can be easily reproducible, by replacing data on consumption by the building under question, local prices of energy and smart technologies, available budget, and priorities. Finally, HVAC systems play an important role, consuming between 30% and 50% of the total energy in buildings, and so, it is the area where improvements would generate, not just, most of the savings, but also improvements in comfort and health. This project shows a variety of possibilities and clarifications that would help some players on the construction and real estate industry to pay more attention and be more open to the use of smart buildings that are friendly with the environment. Also, it could help tenants on deciding themselves on implementing smart technologies on already existing buildings, either in an integrated way or simply individually, depending on their limitations and priorities.