With the evolution of technology, humans are nowadays able to control many factors that influence indoor environmental quality (IEQ) such as temperature, air quality, and air velocity. Thus, we can create a comfortable environment in buildings but on the other hand, this progress also leads to a higher energy consumption. Obviously, we aim to consume as little energy as possible to lower the environmental impact, but since we spend about 90% of the time inside of buildings, we should not underestimate the importance of good IEQ. Indoor conditions have a relevant influence on our ability to work efficiently and on our general health. In order to analyse the connection between human productivity and energy consumption we chose to focus on office buildings. How can we provide good IEQ – and consequently reach a high level of productivity – and, at the same time, reduce the energy consumption?
Facts and numbers
Buildings consume about one third of total primary energy resources and produce 30% of CO2 emissions. As shown in the graph below, heating and cooling with HVAC systems represent about 39% and lighting 25% of energy consumption in an office building. This means that about two thirds of the total energy is used for IEQ.
It is in the company’s interest to maintain high IEQ as it has a direct influence on people’s well-being and therefore on their productivity. Comfortable room temperature (between 20°C and 24°C) alone can raise human productivity by as much as 3%. [6] Furthermore, if we consider the optimization of indoor air quality (IAQ) we observe an increase of additional 11% in productivity and another 2% thanks to well adapted lighting. Therefore, we can reach a total of 16% increase in productivity. [6] At the same time, these improvements help to avoid sick building syndrome (SBS) symptoms (headaches, fatigue, asthma, ect.) and building related illnesses (BRI) which are health issues with physical signs that persist. Preventing SBS and BRI reduces the workers sick days and helps to maintain productivity.
Furthermore, the increase of productivity achieved through thermal comfort can boost the turnover by twelve to 125 billion dollars annually, while improving the energy efficiency without taking into account human comfort saves only between six and 20 billion dollars (for a small business). [3] In conclusion, if we consider the finances only, it is advisable to invest in the maintenance of high IEQ rather than saving money by reducing the energy consumption of HVAC and lighting. But of course, reducing the energy consumption in office buildings is still of interest for a company: on the one hand to lower the costs and on the other hand – as already mentioned – to lower the environmental impact.
In 2009 the University of San Diego made a survey for which they questioned over 500 managers after moving into an energy labelled building. Over 40% of them observed an improvement of productivity of their employees and a diminution of sick days and, in some cases, even a raise of employee’s moral. [9]
Briefly and succinctly, we aim to reduce energy consumption without causing a productivity loss of the occupants, or maybe even improve it. Since these two aspects are clearly in conflict, some potential solutions to the problem are proposed in the following.
How can we solve the conflict between human productivity and energy consumption?
One possibility to reduce the needed amount of energy is to use the building as a storage by taking the cold night air to cool the building and save energy normally used for cooling throughout the day. Or – in the opposite case – allow the building to warm up during the day to save energy normally consumed to heat the structure throughout the night. In order to make these possibilities operational we would need to install some openable windows. This is an additional way to lower the energy use, since it would make it possible to generate a greater air velocity if the building gets too warm during the day.
Openable windows also have a positive impact on the psychology of the occupants due to user empowerment. Additionally, the greater number of windows would as well increase the amount of natural lighting which can be very important since it makes you less sleepy by the end of the day and your cortisol levels drop significantly. This would improve the well-being of the building’s occupants and therefore their productivity would rise by about 0.7-23%. [7] But it is clear that weather conditions do not always permit natural ventilation through openable windows. To ensure appropriate ventilation – since this also has an important impact on human productivity – it is advisable to complete the setup with HVAC systems. In the following graph, several options of ventilation are proposed.
Of course, the climatic environment of the building must be critically analysed to choose the most efficient ventilation setup.
Since the optimal thermal condition is very individual for every occupant, this concept of hybrid ventilation systems could be combined with installing small devices (like fans or little air conditioners) at each workstation which would allow everyone to set the temperature and air velocity as they prefer. Thus, the occupant’s moral, and therefore their productivity, can be significantly increased.
From the given facts, we can see that it is only possible to achieve small improvements in productivity while saving a little amount of energy at the same time. If you focus on just one of the two issues, it is very probable that the other one will be negatively affected. This is exactly where we have a conflict between human productivity and energy use. For example, if you reduce the air conditioning in summer to save energy, the occupants will suffer from hot and stale air and therefore their ability to stay focused will significantly be diminished. Thus, it is very important to carefully consider all aspects in order to find a compromise between energy efficiency and IEQ. [2]
Jonathan Wolf, Thamin Maurer, Marc Touré, Sarah Pupo
Sources:
[1] “Natural ventilation simulations”, <https://eeabs.co.uk/natural-ventilation-simulations/>, 23. November 2020
[2] David P. Wyon: “Enhancing productivity while reducing energy use in buildings”, <https://www.rand.org/content/dam/rand/pubs/conf_proceedings/CF170z1-1/CF170.1.wyon.pdf>, 23. November 2020
[3] “50 energy saving tips for small businesses”, <https://business.directenergy.com/50-energy-saving-tips>, 23. November 2020
[4] William A. Ruch: “Measuring and managing individual productivity”, <https://www.nap.edu/read/2135/chapter/6>, 23. November 2020
[5] “Energy use in buildings”, <https://ec.europa.eu/energy/eu-buildings-factsheets-topics-tree/energy-use-buildings_en>, 23. November 2020
[6] Marc Howe: “How intelligent buildings can enhance human productivity”, <https://sourceable.net/intelligent-buildings-can-enhance-human-productivity/>, 23. November 2020
[7] “Productivity gains from energy efficiency”, <https://buildingefficiencyinitiative.org/articles/productivity-gains-energy-efficiency>, 23. November 2020
[8] “Typical energy consumption breakdown in an office building”,<https://www.researchgate.net/figure/Typical-energy-consumption-breakdown-in-an-office-building-6-3-Background-to-the_fig1_317622121>, 23. November 2020
[9] “Green Buildings and Productivity <https://catcher.sandiego.edu/items/business/Productivity_paper_with_CBRE_and_USD_Aug_2009-Miller_Pogue.pdf>, 23. November 2020