Presented by: Julia K. Day
Relevance / Problem / Context High performance buildings are intended to optimize energy use, health, and comfort to occupants. However, in many high performance buildings, occupants frequently complain about thermal conditions. At times, stringent energy efficiency goals and the design strategies employed (such as natural ventilation or daylighting) may unintentionally eclipse occupants’ thermal comfort. Thermal comfort is defined as a person’s cognitive state that expresses satisfaction or contentment with their surrounding thermal environment (ASHRAE 55). Thermal comfort is extremely complicated because there is a wide range in people’s perception of comfort due to various indicators including air temperature, radiant temperature, air velocity, humidity, amount of clothing insulation, and metabolic heat (Holopainen et. al, 2014). Other factors may also include personal preferences, gender, body composition, or location within a given building (ASHRAE 55). Cultural expectations and standards for thermal conditions may also play a role in thermal comfort. It is important that interior designers understand (1) thermal comfort, (2) what they can do about it, and (3) how occupants interact with the building to maintain thermal comfort. Previous studies have found that occupants may be more willing to tolerate wider temperature ranges in naturally ventilated buildings when they are given the option of control (i.e. opening windows themselves) (Humphreys, 2005). If occupants accept a wider range of temperature as “comfortable,” then less cooling and heating will be required, therefore reducing energy use. However, it is important to understand that when occupants are given control over their thermal environments through operable windows, while this control may help maintain their personal comfort for some, it may disrupt others’ thermal comfort, and may actually negatively impact the energy use in a building if windows are opened (or left open) when outdoor temperatures are too high or too low to support energy use goals (Ackerly et.al., 2012). Oftentimes, high performance buildings are fitted with active control or signaling systems that notify when conditions are appropriate for opening windows (i.e. air quality, temperature or humidity). In these cases, it is crucial that occupants are appropriately educated on these systems to maintain thermal comfort. Thermal comfort in buildings is a complex issue because people simply have different preferences, and furthermore, their behaviors can impact others’ comfort and energy use. For example, someone may bring in a space heater because they are cold at work. This may seem insignificant to most, however, in a high performance building with finely tuned HVAC setpoints and aggressive energy reduction goals, these simple behaviors can be detrimental. Method / Findings This study employed a meta-analysis approach, which identified and synthesized thermal comfort survey and interview results from multiple case studies and post occupancy evaluations (POE). Data were aggregated and coded to better understand thermal comfort preferences and trends, occupant behaviors in relation to thermal comfort, and best practices in design for thermal comfort. Findings of this study demonstrated the importance of thermal comfort in the workplace, especially with regard to productivity and environmental satisfaction. Advancement of design knowledge Thermal comfort is an issue that arises repeatedly in a wide array of multi-disciplinary research and literature. Many believe that thermal comfort is a problem best left to the engineers. However, there are moves that we, as designers, can make in interior environments to alleviate issues of thermal comfort that range from shading, spatial layout, psychological factors, and programming for variation in thermal environments. There is an opportunity for interior designers to better understand how to design for optimal thermal environments.
- Ackerly, K.; Brager, G.; & Arens, E. (2012). Data collection methods for assessing adaptive comfort in mixed-mode buildings and personal comfort systems. UC Berkeley: Center for the Built Environment. Retrieved from: http://escholarship.org/uc/item/64p9111k.
- ANSI/ASHRAE Standard 55. (2004). Retrieved February 26, 2014, from https://www.ashrae.org/standards-research--technology/standards-interpretations/interpretations-for-standard-55-2004
- Holopainen, R., Tuomaala, P., Hernandez, P., Häkkinen, T., Piira, K., & Piippo, J. (2014). Comfort assessment in the context of sustainable buildings: Comparison of simplified and detailed human thermal sensation methods. Building and Environment, 71, 60–70. doi:10.1016/j.buildenv.2013
- Humphreys, M. A. (2005). Quantifying occupant comfort: are combined indices of the indoor environment practicable? Building Research & Information, 33(4), 317–325.