Thermal Comfort in a Healthy Building strategy

 


Healthy buildings / thermal comfort / wellness real estate / well building standard

Biophilic Interior Design


What is thermal comfort in a healthy building?

Heating and cooling tend to account for around half of a building’s energy consumption, making thermal comfort a key consideration for a green building’s overall energy use. In addition, thermal comfort is considered one of the leading factors in occupant satisfaction within the built environment, making it a vital component of a healthy building strategy too.

Spaces that are perceived as being too humid or warm have been shown to lead to decreased productivity, increased sick building symptoms (such as cognitive impairment and sleepiness) as well as negative mood states (ref: WELL Building Standard).

As a result, a comprehensive thermal performance plan which includes strategies such as thermal zoning, individual thermal control, and monitoring thermal characteristics within the building is now firmly part of the green & healthy building consultant’s toolkit.  

Thermal Performance in Real Estate

To achieve acceptable thermal comfort within an interior space, healthy building standards such as WELL designate that 80% of occupants must consider a space to be comfortable - a qualitative (subjective) response. As thermal comfort is determined by the level of perceived comfort from building occupants, it is impossible in this case to lay out a plan based specifically on pre-agreed numbers. 

The healthy building standards therefore predict what will cause comfort in spaces through a range of environmental factors such as temperature, humidity, outdoor temperature, occupant density and activity, air movement and more. However, even with all these data points in front of us, getting it right for everyone can be challenge, especially in a workplace environment with both men and women sharing the area.

This is due to varying occupant perceptions of comfort, so even more specific zoning strategies by space type / activity for example as well as providing individual thermal comfort control provide opportunities for further refining a thermal comfort plan. When building occupants are comfortable with their thermal environment, productivity increases and levels of fatigue are reduced (WELL). 

Thermal Zoning and temperature in a healthy building

When considering the thermal characteristics of a space, the type of activity taking place in that interior area matters greatly. For example, a hotel gym where guests are exercising and emitting body heat will need not just higher ventilation rates to remove the CO2 but also a lower temperature.

A study space such as a school library will be very different in that sense, although again there are considerations around optimal temperatures for cognitive performance and concentration. Breaking a building down into a number of such activity zones can help ensure suitable thermal conditions, leading to enhanced occupant satisfaction.

Temperature can therefore be influenced by a variety of factors such as human activity, building location and orientation, as well as the type of ventilation strategy - be that natural, mechanical or a combination of the two (WELL). When designating different zones, it is important to consider these various factors in order to regulate the thermal properties of each area in advance of building occupants using the space. 

Generally, HVAC ventilation systems are responsible for maintaining thermal conditions, and therefore can be used to create different thermal zones within a building, with the level of zoning precision depending on the HVAC set-up. When natural ventilation options are in use, it is operable windows that are used to regulate temperature and thermal comfort. 

Towards Individual Thermal Control in a Healthy Building

Individual thermal controls can be used to further delineate zones and create smaller, more personalized areas even within rooms. Strategies such as individually accessible thermostats, fans, flexible dress codes, or easily accessible operable windows can all help contribute to giving individuals a sense of control over their thermal experience indoors.  

No one space will please everyone, especially if there is a mix of ages, genders, and so on. It is clear that women tend to be a few degrees colder than men, and tend to be more sensitive to changes in temperatures (Allen), they also are less likely to be in a full trouser suit every day in formal work environments, as men are (in certain industries) no matter what the season.

In addition to individually manageable thermal controls, the provision of outdoor space such as courtyards or rooftops can provide places of respite to allow building occupants to adjust their comfort levels. Access to the outdoors not only provides space to increase thermal comfort, but also can provide other benefits such as biophilia, which improves mental health and can restore focus. 

Monitoring & Displaying Thermal Characteristics in a Healthy Building

Sensors that monitor and regulate indoor air temperatures should be placed intentionally to gauge if any unexpected deviations occur. As with other smart building systems, thermal comfort should also be monitored to provide feedback to building managers and inform potential changes. 

Generally, the same sensors can be used to regulate various thermal factors such as temperature and humidity, as well as other interior environmental characteristics such as air quality, for example. Regular commissioning and maintenance of building systems is also imperative to promptly respond to any thermal problems that occur (Allen).  

When coupled with occupant preferences and surveys, the combination of thermal data and occupant satisfaction can be applied to provide optimal thermal comfort. Building occupants should be surveyed regularly to maintain desired thermal levels and to gauge comfort. 

As thermal preferences vary greatly from person to person and are harder to measure numerically, information from post-occupancy surveys is especially important, giving us perceived comfort feedback as well as hard thermal data to work with.

Sources

Allen, Joseph. “The 9 Foundations of a Healthy Building.” For Health, Harvard T.H. Chan School of Public Health, https://forhealth.org/9_Foundations_of_a_Healthy_Building.February_2017.pdf

WELL Standard v2