Wellbeing in buildings
Thermal comfort
W
hen we think about thermal comfort in the workspace, it is advised to avoid confusing the term with air quality especially as the two differ. Air quality tends to pertain to controlled environments such as
laboratories, where contaminants and pollutants must be removed or displaced. The minimum fresh air must also frequently vary according to the often variable occupancy rate.
Whilst air quality is more concerned with the reduction of harmful particulates
in an occupied zone, thermal comfort has more of a relation to employee health and wellbeing. As buildings must be designed with employee health and wellbeing as a priority, sophisticated air distribution systems must be able to provide a high standard of thermal comfort. To ensure optimum thermal comfort is maintained in occupied zones, businesses selecting air distribution systems are advised to acquaint themselves with the standard: BS EN ISO 7730:2006, ‘Overview of design regulations for thermal comfort’. This industry standard predicts the estimated percentage of occupants which could be dissatisfied with the level of thermal comfort in a space. ISO 7730 analyses the ‘predicted mean vote’ (PMV) with the ‘predicted percentage dissatisfied’ (PPD) to look at comfort limits. Companies including Krantz design, manufacture and select equipment to this standard in order to ensure optimum comfort levels are achieved in a working environment. But how is this type of dissatisfaction measured? Dissatisfied occupants are those who see their working environment as a hindrance to their health rather than an enhancer. Poor thermal comfort can result in sickness, less productivity and more staff complaints. The BS EN ISO 7730 industry standard stipulates how a building’s thermal comfort category, whether it is A, B or C, determines the percentage of dissatisfied occupants. Essentially, companies can use this standard to see what level of thermal comfort they desire. With A the highest and C the lowest, buildings fulfilling a CAT A criteria ensures less than 6% of occupants are displeased with thermal comfort. Considering only an average of 6% is uncomfortable, it is well worth designing to a higher specification to assure wellbeing is not compromised.
How do we measure thermal comfort?
In order to ensure a building’s inhabitants are satisfied with the level of thermal comfort, six factors need to be considered. These are: • Air temperature: including the supplied air temperature • Mean radiant temperature: mean temperature of all surfaces in a building
28 January 2019
www.heatingandventilating.net
and wellbeing
Sustaining a good level of thermal comfort in the workplace can pose its challenges. Denis Kerr, sales director at Krantz, explores the significance of providing a high level of thermal comfort in working environments, looking at its impact on employee productivity and health
• Air velocity in the occupied space: measured at m/s • Air humidity • Clothing: different layers affect body temperature • Activity: The nature of the job affects body temperature, whether it is manual or sedentary
All of these factors are interrelated and, when considered in equal measure,
increase the productivity of employees working in commercial spaces. Regardless of whether a building’s thermal comfort is CAT A, B or C, all of these factors must be considered to ensure employee satisfaction in an occupied space - one element cannot function without the other.
Why is the ISO 7730 standard important?
The 7730 standard is a highly important regulation, where companies can call in air distribution experts to ensure all aspects are considered and implemented in order to ensure employee health and wellbeing is not compromised. An example of how the ISO 7730 standard has changed the way thermal
comfort is categorised is as follows. In order to ensure thermal comfort to a CAT A standard, historically, the accepted velocities in the occupied zone have been 0.25 m/s max velocity; however, this has changed in light of ISO 7730, where the velocity in the occupied zone must be under 0.16 m/s in most commercial buildings and compatible with the room temperature in CAT A buildings. In most cases, the hotter the environment the higher the velocity of air permitted in the space. CAT A environments should include commercial spaces, having lower air velocities due to the environment: people sit in one place with one layer of clothing on. However, it may be considered that areas such as car manufacturing plants permit a higher velocity as workers move more, carry larger loads and wear heavier uniforms. By aligning the right temperature with the correct air velocity, thermal comfort
is guaranteed, making sure people feel relaxed and comfortable at work. This in turn minimises stress or anxiety levels, improving workflow and health in the workspace. Thermal comfort is a key building consideration which companies are advised
to consider carefully and to provide the best conditions for employees. The ISO 7730 industry standard is the coherent rubric for companies to adhere to. By supplying higher levels of thermal comfort in the workspace, the health and happiness of employees will be improved and more importantly the standard, when applied, will accurately predict occupant satisfaction.
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