A Passive House University Residence Building

In order to meet its 2040 emissions targets, the University of Victoria is utilizing Passive House standards to construct two new residence buildings. This case study explores the application of future-adjusted weather files to ensure that both the energy budget requirements and the thermal comfort of inhabitants in the buildings are met well into the future as the climate continues to warm.

Key Points

  • In order for buildings to meet their functional and design objectives (e.g. thermal comfort of inhabitants and energy efficiency) well into the future, the design phase needs to incorporate both historical climate data and future climate projections.
  • The availability of locally relevant, future-adjusted climate data should be assessed as early in the design process as possible, as historical analogues may no longer be valid.

David Adams is an Energy Manager at the University of Victoria (UVic) working to reduce energy consumption. He played a role in the design of two new residence buildings, one of the most significant energy efficiency initiatives on campus to date. Facing a need for more accommodation for students, UVic had decided to opt for Passive House construction as part of its target to achieve net zero emissions by 2040, roughly in line with what is required by the UN Paris Agreement to keep global warming within 1.5ºC by the end of the century. Passive House is a voluntary building design standard that uses superinsulation, heat recovery ventilation, window placement and size, and active energy management, amongst other techniques, to passively collect solar energy as heat in the winter and achieve very low or even zero net energy consumption (in cases where renewable energy is generated on-site). The design can ensure that body heat and the internal heat gains from appliances, lighting, and electronics can be used to heat a space without compromising comfort.

As a result, when construction of the two towers is completed, the university will have replaced the roughly 40 dormitory beds that an old residence building provided with over 700 beds while still achieving a significant net decrease in the campus’s greenhouse gas emissions. Moreover, the addition of a cafeteria and lecture theatres serving all UVic students assists in further densifying the campus profile, reducing land use and benefiting local ecology.

But in order to achieve this goal, David needed help finding suitable climate data to simulate the proposed buildings’ performance under various climate scenarios.

Passive House design requires careful consideration of how climatic factors affect the thermal comfort of inhabitants. For example, the building’s orientation relative to the sun and the placement and size of windows are important to make use of or avoid “thermal gains,” depending on the season. Also, the Chartered Institution of Buildings Services Engineers’ thermal comfort standard, TM59, specifies that interior temperatures should exceed 26ºC for no more than a total of 3% of the year (or 1% of the year for nighttime temperatures). Failing to consult future temperature projections for the region could result in the building behaving like a greenhouse, resulting in the undesirable outcome of overheating.

“With no other future climate data available for design at the time, our design team used historical climate data from Abbotsford because the city regularly gets hotter summers than Victoria.”

-David Adams, Energy Manager: University of Victoria

Using Abbotsford as an analogue for a future Victoria made sense initially because of the significantly warmer mean summer temperature in the mainland city, compared to its coastal counterpart, over the historical period.

The engineering consultants were already at work using the Abbotsford data when David and his colleagues reached out to the Pacific Climate Impacts Consortium (PCIC) at UVic. PCIC was contacted because of their experience analyzing climate data across BC and in the Victoria region specifically. PCIC adapted the hourly climate information that is currently used in assessing thermal comfort in buildings to produce new versions of the datasets that account for future climate change. These “future weather files” are meant to represent typical conditions for the 2050s and 2080s, under different climate scenarios. When the designers accessed this information, they realized that in 2050 for the scenarios chosen, the summers were actually projected to be considerably warmer in Victoria in the future than they are in Abbotsford in the present. This meant that the design as configured (in particular the mechanical equipment) for the historically hottest summers in Abbotsford might not be sufficient to ensure thermal comfort in Victoria in the future.

“It wasn’t quite an ‘Oh crap’ moment, because it was still sufficiently early on in the process, but this did require us to review and re-size some of the heating and ventilation design; move a window from over here to over there, and so on,” David says.

The energy constraints imposed by the Passive House design are significant, so these findings have implications beyond thermal comfort alone. Given that the two towers will be among the largest Passive House certified buildings in North America, UVic worked closely with the Darmstadt-based Passivhaus Institute, a leading research institution which also provides certification and expert consultancy services in the design of a wide range of Passive House building types. Given the scale of ambition, the exercise was novel even for them. For example, restaurants are very energy intensive and normally do not fit within the Passive House model. But the cafeteria UVic had envisioned would be substantial, servicing the entire campus. Consultations even took place between UVic and the Institute over the food menu in order to reduce energy consumption in the kitchen, meaning fewer hot food items like pizza and hamburgers and more cold ones such as sandwiches and sushi.

Looking at the long-term climate projections from PCIC, Adams and his team also realized that by 2080 their design would no longer be able to meet the space cooling requirements to keep inhabitants within a healthy standard of thermal comfort (Figure 1). This prompted a debate as to whether to completely overhaul the design (which would require substantial cost increases for an alternative cooling system), or to not address this issue yet, since potential changes to building requirements six decades into the future are largely unknown. The overhaul would be much more expensive and require an entirely different type of mechanical equipment. The team concluded that adding the alternative cooling system would require major sacrifices to the core functionality of the building in order to fit it within the project budget, and was therefore not financially feasible.

Figure 1. Increasing building overheating risks with time

A conceptual illustration of the increasing overheating risks in a building designed using historical weather data, as outdoor temperatures increase with climate change.1

In the end, the team chose to stick with the solution that had improved the original design in order to meet the more severe summer conditions projected for Victoria in the 2050’s. But the realization that significant changes to a building design would be required simply depending on whether the assumed future time horizon of the building should be 30 years versus 60 years gave them pause. It brought home the difficulty, but also the necessity, of making local adaptation decisions today based on the best available, future-looking climate information that science can provide.

References

  1. BC Housing (2019). BC Energy Step Code: Design Guide Supplement S3 on Overheating and Air Quality. Online: https://www.bchousing.org/research-centre/library/residential-design-construction/bc-energy-step-code-design-guide

Future Weather Files

The BC Energy Step Code requires energy modelling for Part 3 and Part 9 buildings, which typically utilizes weather files of historical conditions. However, future-adjusted weather files for locations across BC are now available for energy modelling. They were produced by applying the high emissions scenario (RCP 8.5) to the most recent Canadian Weather Year for Energy Calculation (CWEC) dataset, for each location in that dataset. The files are produced for three different 30-year periods (2020s, 2050s, and 2080s).

Related Variables

Explore variables to learn about how data was used to impact climate related decisions in specific contexts.

Cooling degree days (CDDs) give an indication of the amount of space cooling, i.e., air conditioning, that may be required to maintain comfortable conditions in a building during warmer months. When the daily average temperature is hotter than the threshold temperature, CDDs are accumulated (see Degree Days Above). Threshold  values may vary, but 18°C is commonly used in Canada.   Larger CDD values indicate a greater need for air conditioning.

Technical description:

The number of degree days accumulated above 18°C in the selected time period. Use the Variable menu option to view the annual, monthly or seasonal values for this index. Visit the Analyze page to calculate degree days using different threshold temperatures.


Tropical Nights (Days with Tmin >18°C) describes the number of days where the nighttime low temperature is warmer than 18°C. 

Hot summer days and heat waves become particularly stressful if overnight temperatures do not provide cooling relief. Tropical nights make it more difficult for the body to cool down and recover from hot days.

Elderly people, the homeless, and those who live in houses or apartments without air conditioning are especially vulnerable during these heat events, particularly if they last for more than a few days.

Technical description:

A Tropical Night occurs when the daily minimum temperature (Tmin) is greater than 18°C. Use the Variable menu option to view the annual, monthly or seasonal values for this index. Visit the Analyze page to calculate Tropical Nights using different minimum temperature thresholds.