Do Our Actions Matter? How Occupant Behaviour Affects High-Performance Buildings
Over the past few weeks, we have thoroughly examined the benefits and potential technological limitations of passive house and deep energy retrofits. We also considered the factors limiting the uptake of these efficient dwellings, both from a consumer and an industry professional's perspective. Assuming that the Canadian government sets optimistic targets, provides generous funding and addresses the labour shortage to convert current and new building stock to meet efficiency standards - will our new energy-efficient building stock live up to its potential?
There are various levels of energy-efficient certification for homes and commercial buildings around the world. The most common certifications in Canada include Energy Star, Leadership in Energy and Environmental Design (LEED), and Passive House. Passive house has stringent construction requirements for airtightness, heat and cooling demand, and energy consumption. The PHI certification is provided after an audit upon building completion while PHIUS has a two-step certification program that requires both the design and final construction to be reviewed. LEED certification has adopted a similar process that reviews registered projects through one or two audits depending on the building type. In both situations, audits and certificates are provided upon completion of construction, assuring that the buildings meet efficiency standards for the given program at the time of audit.
It is important to note that most efficiency certification is provided before humans occupy the dwelling. In fact, these standards are based on computational modelling which simulate occupant behaviours rather than conducting a long-term performance review assessing the actual influence of human behaviours. This can result in an alarming performance gap between the predicted and actual energy consumption of a building. Research shows that actual consumption can be up to 300% greater than expected consumption from modelling in some high-performance building standards like LEED but much smaller in others such as passive house.
Photo byJaye Haych
While the psychological impact of a building's efficiency on occupant behaviour is relatively unexplored, evidence suggests that a building's energy consumption is more susceptible to occupant behaviour as envelope performance increases. In contrast, other research has found no positive correlation between increasing a building's energy efficiency and occupant energy consumption. Instead, it suggests that heat use was reduced by 64% post-renovation. While these results are heavily contradictory, it shows how dynamic human behaviour combined with varying building forms produce unknowns in this emerging field.
Although the impact of occupant behaviour on a building's performance is debated, it is generally accepted that the success of energy-efficient design strategies depends on how occupants interact with the building. As mentioned previously, building use is a crucial variable affecting energy performance. For example, a facility designed to function as an office will not perform optimally if the space is later converted for high energy and heat activity. However, while some passive designers are now accounting for varied occupant use through the seasons, the psychological and cultural influences on occupant behaviour aren't generally considered.
It's been noted that the expected thermal comfort level varies by culture. In many European countries, locals have a 15°Δ expected comfort range. In the summer months, Europeans endure warmer temperatures by wearing lighter clothes and avoiding activity during peak temperatures, and in winter, they layer clothing both indoors and out. In the USA, there is a 2°Δ expected comfort range. Americans generally want to live in homes with a set temperature of 68 - 70°F regardless of the outside weather conditions. This means that homes with a 9°Δ as certified by most energy-efficient standards will perform poorly under culturally influenced occupant behaviour in North America.
Photo byGiulia Bertelli
So what does this mean for homes built to LEED or passive house standards in North America? In general, while influenced by occupant behaviour, passive houses meet their certified standards. On the other hand, it appears that LEED-certified buildings are more susceptible to a resident’s habits. For example, in 2016 in Vancouver, BC, many LEED-certified buildings failed to meet efficiency targets once the space was occupied. It is unclear as to what degree occupant behaviour is influencing these buildings to fail their LEED certification, regardless, it shows that computational modelling is not sufficient to ensure these buildings perform as intended. Inconsistencies in evidence around this issue have allowed some to argue that these efficiency standards are ineffective and act as a costly cover-up for governments to maintain environmental prestige. While similar stories from the USA allow such arguments to gain momentum, they are tacked onto agendas that seek to discard these standards rather than improve them.
It is important to note that not all buildings certified to LEED or passive house standards will fail to meet the modelled energy use for their certification. However, while it's been shown that these dwellings can effectively reduce energy consumption, an equal amount of research suggests their effectiveness is questionable, especially the lower levels of LEED certification. Again, there is research showing that passive house has fewer issues on this front than LEED. It also highlights the importance of accounting for embodied carbon, where energy/carbon savings are independent of energy efficiency. It is clear that as high-performance building standards become more popular, issues with the certification system become more evident. We currently lack the mechanisms to require operational performance data from certified buildings past the initial modelling and audit phase which is a major barrier to improving these standards. As evidence on the effectiveness of LEED and passive standards vary, extensive research is needed to show how psychological and cultural influences on occupant behaviour affect a building's long-term performance. Until then, designers and builders must discuss and consider such variations in building use with their clients where possible.
Articles on the PBC website reflect the views of the author and not necessarily those of PBC.