Rethinking Comfort: Take Back Control

Should we be adapting to our environments using our own intervention rather than relying of technology?
Marc Seligmann, Head of Sustainability discusses 

Is our understanding of thermal comfort allowing us to design environmental conscious buildings? The design of our heating and cooling systems is historically based upon providing a universal thermal comfort but achieving the “right” temperature for occupants is fraught with issues. Something we’ve found in our own office where there have been tensions between people feeling too hot or cold. A review of current and past research questions whether thermal comfort standards need an industry review, providing better individual control and expecting users to change behaviour based on conditions rather than aiming for prescribed set point temperatures.

Ultimately, are current standards leading us to overdesign both our systems and building fabric and hindering efforts like retrofit because we have neither the economic nor carbon budgets to achieve these standards.

The Climate Crisis

Much has been written on whether we have the carbon budget to build even a modest number of homes but even within the context of current political targets around house building we will need a drastically different approach to materials and carbon. Thermal comfort plays an important factor in influencing both these issues. It is often stated that reducing the thermostat temperature by 1°C can save 10% of the space heating bill so any changes to how much we heat or cool our buildings are significant in terms of energy conservation. This creates a waterfall effect to higher fabric and building services requirements and greater environmental impact.

What is Comfort?

Thermal Comfort in simple terms is not being too hot or cold but its definition in building design is more complicated. Clothing, temperature, wind speed, humidity and activity level all effect our level of comfort but so does ethnicity, geography, culture and social factors. For example, how we expect the home to be heated can be influenced by clothing choices based on fashion or social status. Western preferences for cooling have shifted away from allowing natural bodily regulation through perspiration. Existing comfort standards either use a prescribed set of criteria which do not represent the difference in how we live in homes or with many cultural and social factors not considered at all.

Redefining Comfort Metrics

Winter

Compared to 1970, homes are now heated approximately 4°C warmer due to central heating adoption. While this has undoubtedly improved living conditions for many, surveys indicate a shift in comfort expectations, with rooms routinely heated above accepted standards.

Current UK heating systems are designed to meet temperatures set by CIBSE and it is assumed thermal comfort is achieved by meeting these limits, however these temperatures are above the limits set by the WHO to prevent illness and design briefs often exceed these values.

Winter design temperatures are built around a particular clothing and activity level, both of which have such a wide variance in homes it makes it almost impossible to find a temperature that is comfortable for all. Should our focus on achieving nirvana set point temperatures change to simply providing better individual control. Moving away from central to individual heating systems. Simply setting a specific temperature can shape our expectations about whether the environment feels too hot or too cold.. This restricted version of comfort can also lead to overestimating savings of energy efficiency measures by assuming a much higher level baseline of heating than may be necessary in real life. Unlike summer comfort, winter comfort temperatures are not adaptive to even external weather conditions.

Summer

The adoption of overheating analysis, utilising CIBSE’s TM 59 methodology, has become standard practice and a requirement of Building Regulations Part O – Overheating. My own concern was that TM 59 was underestimating the risk of overheating in homes. However, a review of current research surprised me.

Interestingly, testing of the CIBSE standard in an Australian climate found that whilst most dwellings were deemed to “overheat” according to CIBSE TM 59, most actual occupants indicated they were comfortable, finding

that the thresholds were too stringent. This aligns with other studies that show comfort models for residential buildings tend to have a wider range of comfort temperature for different countries and climates. Studies have shown that Malay residents in London had a comfort temperature 3°C lower than those in Malaysia. This highlights the issue of defining thermal comfort through a universal standard which does not account for climate and cultural preferences, nor consider much of the adaptability of occupants.

Current trends from overheating studies show that a form of mechanical cooling is now required to avoid overheating in UK in almost all circumstances for even the current weather conditions. This comes with a huge economic and environmental cost. How is it that other populations have adapted to higher temperatures without this need?  More research could inform sustainable practices and our guidance around overheating in homes. We do not want to go down a path where we need ever increasing levels of cooling in a self-fulfilling spiral of comfort and mechanical cooling.

Conclusion

We need a fundamental shift in how we design and interact with our homes to meet thermal comfort. Our designs are defined by comfort standards influenced and set by an inflexible series of assumptions leading us to install ever more material and building services. In the context of the climate crisis, we cannot continue to move in this direction, particularly as housing continues to use high levels of energy.

As demand on the electricity network continues to rise, meeting an ever-increasing level of comfort becomes increasingly untenable. Our preliminary research on comfort reveals a consistent trend: both winter and summer conditions are witnessing a steady increase as occupants strive for ever demanding levels of comfort, resulting in higher demands for heating and cooling.

We support additional research on achieving comfort in housing to ensure our designs remain environmental conscious. For those interested we ask you to join our research partnership to build more knowledge and understanding on these issues.