We spend a large amount of our time indoors - some studies estimate around 90 per cent - so clearly, we want our homes, offices, restaurants and classrooms to be comfortable and healthy and to make us feel well. Most of all, we want our buildings will keep us warm in winter and cool in summer. It is no wonder, then, that heating, ventilation and cooling systems account for about half of the buildings' energy consumption.
But can we heat and cool buildings more efficiently and effectively? The first challenge is getting the right temperature. The most widespread method used for creating a comfortable temperature in buildings seeks to provide optimal thermal comfort for most people occupying a given room.
The model focuses on a combination of factors: air temperature, mean radiant temperature, air velocity, relative humidity, clothing insulation, and activity level.
However, data show that following this approach, only 11 per cent of buildings in the US meet the 80 per cent threshold of satisfied users.
So in many cases, buildings are maintained at an uncomfortable temperature. This is important because the temperature significantly affects office workers' performance. The thermal environment also directly affects humans' integumentary, endocrine, and respiratory systems.
The importance of air quality
Heating and cooling systems have an important role in ensuring indoor air quality. The air inside buildings can be highly polluted due to several different contaminants.
Carbon Dioxide (CO2) is a general predictor for indoor air quality, as keeping CO2 levels below harmful thresholds can help decrease concentrations of other airborne pollutants generated from indoor sources. Other pollutants that can be found in indoor environments are particulate matter, volatile organic compounds, ozone, radon, and carbon monoxide.
Exposure to these pollutants can lead to short and long-term negative health and well-being outcomes, from headaches, eye irritation, rhinitis, and dizziness to asthma attacks and severe respiratory health issues, such as lung cancer.
They also have an impact on work performance. In one study, researchers introduced a 20-year-old carpet into an office, which slightly increased indoor pollutants.
Even if only a small percentage of people in the office expressed dissatisfaction, there were still observable effects on performance: people working on keyboards typed less text and with more typing mistakes when the carpet was in the room.
The role of new technology in reducing energy consumption
To address these issues, significant advances have been made in the field of heating, ventilation and cooling systems in recent years. Sensors to monitor indoor air quality are increasingly available, helping to raise awareness. Research is also exploring ways to optimise older systems.
For example, fuzzy logic controllers can use a wider range of human comfort criteria to bring the space to comfortable conditions while reducing energy consumption.
Another approach is based on personal comfort models, which aim to predict individual thermal comfort responses and aggregate them to find the right temperature for a group.
Occupants can express their preferences using different user interfaces, and control algorithms can modulate the system to deliver optimal indoor conditions. Delivering tailored thermal conditions to building occupants can have a strong impact on environmental sustainability.
For example, enabling real-time individuals' online requests for setpoint variations can reduce energy consumption by 10 per cent, and a consensus-based temperature control model can lead to up to 20 per cent savings. 24 per cent of energy savings can be achieved by modifying temperature setpoints to occupants' complaints.
The study suggests that when setpoints are determined allowing slight deviations from "ideal" temperatures, the energy consumption of the average heating, ventilation and cooling system can decrease even by 50 per cent.
