Thermal comfort VS Carbon emissions

Is thermal comfort more important than low carbon emissions when designing workplaces?

by Kawin Dhanakoses

Sustainable Theory and Context 2014

Supervisor: John Brennan

Edinburgh School of Architecture and Landscape Architecture | University of Edinburgh | UK


Most of people spend 8 hours or longer working every day. Workplace becomes one of the most important spaces that affects people’s daily lives. It is vital that these workplaces, such as commercial sectors, manufacturing industries or offices are able to maintain their profitability of their business in order to generate an economic sustainability. The level of employee’s motivation, performance and productivity are affected by the quality of working environment (Leblebici, 2012). Thermal comfort is one of the physical components which indicate the quality of working environment. It is defined as ‘the condition of mind which expresses satisfaction with the thermal environments.’ (ASHRAE, 2009) It is a subjective term because it is not only influenced by physical environment but also depends on individual’s feelings and perception. Turning on the air-conditioning or radiator to adjust the air temperature to make you feel comfortable, requires energy and inevitably Carbon dioxide is emitted along with the energy production process. As global warming phenomenon raises global temperature and results in unpredictable climate changes, it forces us to use more energy for heating and cooling spaces in order to get back to the comfort zone. As a consequence, more Carbon dioxide is emitted to the atmosphere and worsens the global warming crisis. This generates the never-ending cyclical loop of destruction and forces us to find an effective solution to relieve the impact of this chain reaction.

Nowadays, Carbon emission has become a very important issue to consider because of its global effect. The main contributor to this is the burning of fossil fuel to produce energy. In the UK, commercial and public buildings account for 20% of Carbon emissions. For developing countries like Malaysia and Thailand, there is a similar rising trend of energy consumption by the building sector which is largely due to the heavily subsidized electricity by the local governments (Kwong, Adam, & Sahari, 2014). Thermal comfort in workplace effects employees’ behavior and performance in workplace. As a consequence, this could result in negative impact of economic of the organization as well. However, many major countries especially China, who responsible for 12% of global emissions (Cong & Yuan, 2003), are paying more attention towards a sustainable development strategy. They believe that by implementing long term goal policies to enhance energy efficiency and improve the overall structure of energy supply, could slow down the increase in energy consumption and produce a sustainable economic growth in future. Moreover, as a consequence of the escalating energy price in the many countries and the raising trends of eco-friendly image of the organizations, which lead to the aiming towards improvement in energy efficiency in order to lower environmental impact as well as the electricity cost. As a result, design trends tend to be targeting towards lowering Carbon emission rather than designing the most comfortable workplace for office workers. Nevertheless, designing the building to consume less energy does not always result in less thermally comfortable.

According to (Chen, Rys, & Lee, 2006) research, factors which influence thermal comfort can be classified into three main categories. First, the environmental factors which includes dry bulb temperature, humidity, air velocity, and radiant temperature. Secondly, the individual differences which includes metabolic rate and clothing of each person, and lastly, the length of time exposure to that environment. It can be seen that the two main aspects to consider in designing a lower Carbon emission thermal comfort environment are the physical behavior of the buildings and adaptive behavior of people.

Conventionally, in the hot and humid climate, air-conditioning systems and mechanical ventilation systems are installed in response of maintaining comfort conditions in offices. Most of the time, this system consumes 30-60% of the total energy consumption of building services (Kwong, Adam, & Sahari, 2014) and by operating with appropriate HVAC control strategies could result in large amount in energy savings (Mathews, Botha, Arndt, & Malan, 2003). In hot and humid countries, many field surveys studies of thermal comfort were conducted in both air-conditioning and naturally ventilated buildings. A research in Jakarta Indonesia identified that the naturally ventilated buildings has a potential to spend less than one twentieth as much as the air-conditioned ones (Karyono, 2000). If required, we can apply appropriate technology or engineering solutions which can help lowering the Carbon emissions while still maintaining thermal comfort level. For instance, applying alternative cooling systems, such as radiant cooling systems, resulted in 15% less Carbon emissions than traditional fan-coil air conditioning systems (Barlow & Fiala, 2007). The study of (Yang & Su, 1997) showed that in hot and humid area, alternative building environmental strategies could be operated to achieve energy savings while still maintaining thermal comfort. They showed that part of cooling system could be substituted by ventilation when tuning up the indoor temperature setting; this could save around 30% of energy and increasing in indoor air velocity could improve thermal comfort level as well. It was estimated that by setting the thermostat set-point higher by 2 degree Celsius, this could save around 2,150 GWh of energy annually in Malaysia, together with a reduction of 3×109 lbs (1.36×109 kg.) of greenhouse gases (Kwong, Adam, & Sahari, 2014). Nevertheless, there is an interesting suggestion that we should emphasis on architectural design rather than engineering aspect. This is because architectural solutions can be long-lasting while the engineering ones tend to be temporary and may require more operational costs (Karyono, 2000).

Another main and most important factor that had always caused unpredictable assumption of data is “human”. Since thermal comfort is determined by the way people perceive the temperature of their environment whether is it too hot or too cold, as a result thermal comfort is usually influenced by many subjective factors, for example, the amount of clothing worn by the occupants, occupants’ level of activity, feelings and etc. Human physiology has become another important knowledge that designers need to know to ensure that majority of people in a space are satisfied with their thermal environment (Nicholls, 1999). However, many studies showed that people can react through a range of responses including behavioral, physiological and psychological adjustments to achieve their thermal comfort (Kwong, Adam, & Sahari, 2014). This adaptive comfort approach provides us opportunities to design lower Carbon emission workplaces yet comfortable through a wider range of thermal conditions. Occupants can adapt themselves to a building’s environment by adjusting their clothing, location or interacting with it (for example; by opening windows). By providing occupants with good adaptive opportunities would result in greater tolerance to environmental variations (Barlow & Fiala, 2007). Furthermore, this is proved to be more important in thermal adaptation of occupants than the slower process of acclimatization (Kwong, Adam, & Sahari, 2014).

A few of the studies such as (Karyono, 2000) and (Yamtraipat, Khedari, & Hirunlabh, 2005) also examines the influence of age, gender, physical conditions and education level towards thermal comfort perceptions. One important “non-thermal” parameter that could be the long term solution to the balance of Carbon emission and thermal comfort design is “the lifestyle of people”. People who were brought up in a modern lifestyle of living in a mechanically cooled indoor environment may have different level of thermal comfort from the more elderly people. To support the argument, the result of thermal comfort studies of naturally ventilated building has shown that occupants in free-running buildings were found to be adaptable to a wider range of thermal conditions than those who staying in air-conditioned buildings (De Dear & Brager, 2002). In Pakistan, people show adaptive behaviour to the warmer environment towards changes in air velocity, clothing level, change of activity level and sweating because the air conditioning system was not widely available in the country (Nicol & Susan , 1996). People who live in the tropical countries showed a higher tolerance for warmer conditions, as we can see that in Thailand the upper bound of acceptable effective temperature for naturally ventilated office buildings was 31.5 degree Celsius (Busch, 1992) which shows that air-conditioned office buildings in hot and humid countries might not require as much cooling energy as we think. From these findings, it can be concluded that adaptive behaviour of human is the key factor for setting thermal comfort standards in the buildings. By considering the characteristics of adaptability with appropriate design strategies, human can adjust their existing conditions to achieve thermal comfort without necessarily relying on mechanically controlled HVAC system of the buildings. As a result, this has led to a great potential for lowering Carbon emission by reducing energy consumption as well as operational cost of buildings.

As mentioned above, this report has shown that Carbon emission plays important role in thermal comfort environment in the global scale. Many studies were conducted to find potential of enhancing energy efficiency as well as various methods of predicting thermal comfort assessment more accurately. While bringing the issue of lowering Carbon emission to the higher priority in designing workplace and concerning more about the sustainability of the whole planet, thermal comfort environment can still be achieved. Architectural design strategy is another key solution as it establishes a long-lasting foundation of how all the systems works together. There are plenty of tools provided for designers such as the Computational Fluid Dynamics (CFD) which was noted to be a useful optimization tool to study thermal comfort in relation to energy savings improvement (Kwong, Adam, & Sahari, 2014). Smart façade design of buildings or appropriate placement of naturally ventilated transition spaces in design are also some examples of design alternatives that could help occupants adjusting themselves to their comfort zone easier without the need for any mechanical cooling (Wang & Wong, 2007).

Lastly, the most and important variable is “ourselves”. Since thermal comfort depends on individuals’ satisfaction of thermal environment, it is almost impossible to satisfy everyone’s comfort at the same time. Fortunately, adaptive behaviour of human allows us to automatically seek for opportunities to adjust building environment to suit ourselves at some level. I agree that factors like culture, social, psychological adaptations of human should be taken into consideration in further study of adaptive model of thermal comfort because these factors have impact on humans’ decision on thermal comfort (Yao, Li, & Liu, 2009). In my opinion, we have over-indulged ourselves through the excessive use of technologies. Especially in hot and humid countries, while most of the buildings are relying on air conditioning system to solve universal problems caused by heat, many researches have proved that by proper design majority of the occupants could be satisfied with their thermal environment without the need of mechanical cooling system (Kwong, Adam, & Sahari, 2014). Moreover, in most of the cases of air conditioned buildings, indoor air temperatures were set too low, resulted in some of the occupants even felt too cold. This shows that we become accustomed to the excessive use of technology to satisfy our own psychological needs with the lack of public concern about the long term impact of Carbon emission.

In conclusion, it is undeniable that thermal comfort and low Carbon emission are both very important in designing workplace. However, if we address the issue of low Carbon emission to a higher priority in designing workplace, this could provide a more effective solution to alleviate global warming crisis which would be more beneficial to every people and sustainability of our planet in long term. By carefully implementing proper environmental design strategy into design and adapting our mindset to be more generous to environment, both low carbon emission and thermal comfort would definitely be easier to achieve simultaneously.

References

ASHRAE. (2009). ASHRAE handbook, Fundamentals 1st Edn.

Barlow, S., & Fiala, D. (2007). Occupant comfort in UK offices – How adaptive comfort teories might influence future low energy office refurbishment strategies. Energy and Buildings 39, 837-846.

Busch, J. F. (1992). A tale of two population : thermal comfort in air-conditioned and naturally ventilated offices in Thailand. Journal of Energy and Buildings 18, 235-249.

Chen, K., Rys, M. J., & Lee, E. S. (2006). Modeling of thermal comfort in air conditioned rooms by fuzzy regression analysis. Mathematical and Computer Modelling 43.

Cong, Y., & Yuan, G. (2003). China’s Sustainable Energy Future : Scenarios of Energy and Carbon Emissions. People’s Republic of China: Energy Research Institute of the National Development and Reform Commission.

De Dear, R. J., & Brager, G. S. (2002). Thermal comfort in naturally ventilated buildings: revision to ASHRAE standards 55. Journal of Energy and Buildings 34, 549-561.

Karyono, T. H. (2000). Report on thermal comfort and building energy studies in Jakarta, Indonesia. Journal of Building and Environment 35, 77-90.

Kwong, Q. J., Adam, N. M., & Sahari, B. B. (2014). Thermal comfort assessment and potential for energy efficiency enhancement in modern tropical buildings: A review. Energy and Buildings 68, 547-557.

Leblebici, D. (2012). Impact of workplace quality on employee’s productivity: Case study of a bank in turkey. Journal of Business, Economics & Finance.

Mathews, E. H., Botha, C. P., Arndt, D. C., & Malan, A. (2003). HVAC control strategies to enhance comfort and minimize energy usage. Journal of Building & Environment 38, 493-498.

Nicholls, R. (1999). Heating ventilation and air conditioning. Oldham, England: Interface Publishing.

Nicol, F., & Susan , R. (1996). Pioneering new indoor temperature standards: the Pakistan project. Journal of Energy and Buildings 23, 169-174.

Wang, L., & Wong, N. H. (2007). Applying natural ventilation for thermal comfort in residential buildings in Singapore. Architectural Science Review 50, 224-233.

Yamtraipat, N., Khedari, J., & Hirunlabh, J. (2005). Thermal comfort standards for air conditioned buildings in hot and humid Thailand considering additional factors of acclimatization and education level. Journal of Solar Energy 78.

Yang, K. H., & Su, C. H. (1997). An approach to building energy savings using the PMV index. Building and Environment .

Yao, R., Li, B., & Liu, J. (2009). A theoretical adaptive model of thermal comfort – Adaptive Predicted Mean Vote (aPMV). Journal of Building and Environment 44, 2089-2096.

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