Designing Buildings for Future Climates in the U.K.

Through a study of four building projects, this article explores how impacts from climate change affect the way we think about designing buildings.

As global environmental policy focuses on minimizing greenhouse gas emissions and the extent of anthropogenic (human-caused) climate change, there is a growing realization that at least part of the anticipated change in climate is unavoidable. Consequently, policies and strategies need to be in place to allow our buildings to adapt to a warmer climate, thereby making them more resilient.

The Design for Future Climate (D4FC) initiative by the U.K.’s Technology Strategy Board (TSB)¹ enabled project teams to consider climate change impacts in the design of new construction and building refurbishment projects in the U.K. It allocated £5 million to approximately 50 projects. WSP (now part of WSP | Parsons Brinckerhoff) formed a team for the purpose of generating a climate change adaptation strategy for four building design projects already in the WSP | Parsons Brinckerhoff portfolio and chosen for the competition:

• Trowbridge County Hall: an office renovation project;
• Great Ormond Street Hospital Phase 2B: a new wing of an inner city hospital;
• London Bridge Station Redevelopment: the revitalization of a major London train station; and
• Westbrook Primary School: a new school.

The TSB report entitled, ‘Design for Future Climate’ explores a number of impacts from climate change and how they might affect the way we think about designing buildings. The report classifies the identified climate change adaptation risks into three categories: comfort, construction, and water (see Figure 1). It is by these categories that the four projects were assessed.

Figure 1 – Climate change adaptation risk categories

In order to generate a climate change adaptation strategy, the primary objective was to process general information about the changing climate, apply a variety of climate scenarios to each project and its unique set of characteristics, and evaluate what the effect might be on the building’s ability to perform its function. UKCP09² future climate data was used on all projects, as was a synthesis of this data into building thermal simulation weather files (available under the Prometheus project³) which present a range of future climate scenarios that vary based on expected global emissions (medium, high, very high), the future date (2030s, 2050s, 2080s), as well as a range of probabilistic determinations (10 percent, 33 percent, 50 percent, 66 percent, 90 percent). For thermal analysis, WSP | Parsons Brinckerhoff chose to show all three future dates, typically under the ‘high’ scenario, and 10 percent, 50 percent, and 90 percent probabilistic determinations.

First Stage – Risks and Opportunities

Figure 2 – Risk categorization

The first step was to determine what climate change risk categories were actual issues for the project in question. To achieve this, a fundamental risk review was undertaken with the client’s involvement in this process. Risks were evaluated to determine their likely impact and the probability of them occurring, given what we understood to be the range of future climates (see Figure 2).

For those risks considered important, a list of design responses or approaches were developed. The scope of these responses/approaches included: design modifications to the existing design process, management solutions, ideas for which implementation can be delayed, or simply a suggestion to monitor certain building-specific or climate-based parameters as a warning sign for action or trigger point for implementation.

This initial stage process was documented in a Climate Change Risk and Opportunities Report, which was intended to give the client and the TSB an understanding of:

• all risks that climate change poses to the building and site;
• the severity of the risks, from the most extreme that may require design changes, to those that only require monitoring; and
• opportunities to reduce or eliminate risk, the pros and cons of these opportunities, and the timeframe to implement them.

Second Stage – Technical Feasibility

The subsequent stage was a technical feasibility assessment. The purpose of this stage was to evaluate the benefit of each initiative and to assign a capital and life cycle cost to give the client enough information to determine whether to make an investment in the suggested design initiatives or whether it might be more fiscally prudent to delay intervention. From this feasibility assessment and cost benefit analysis, a climate change adaptation strategy was developed and presented to the client for their consideration.

General thoughts on the climate change adaption risks to the four projects

Comfort – We need to adapt our buildings so that people can live and work in comfort as the temperatures rise. Innovations in design are essential to meet the challenges of hotter summers and warmer winters, while reducing the amount of energy we use. (‘Design for Future Climate’, Bill Gething, page 12)

• When designing for future climate, it is important to avoid relying on air temperature as the sole determinant for thermal comfort and to consider alternative measures which include:
  • Resultant temperature which is essentially an average between the air temperature and the mean radiant temperature, and is a better indicator of how a person will feel in a space, given the impact of the temperatures of surrounding surfaces.
  • Predicted mean vote which is a mathematical model defined in ASHRAE⁴ 55 that considers not only air temperature and mean radiant temperature but also humidity, clothing, activity and air speed.
  • Adaptive thermal comfort is specifically designed for testing natural ventilation designs where opening windows is the primary source of comfort modulation. The model varies the acceptable resultant temperature based upon the external conditions and hence allows for the intuitive phenomenon that “people get used to” higher temperatures and over the years will acclimatize to a warming environment.
• Initiatives such as façade shading, glazing performance, exposed thermal mass, and alternative HVAC strategies that feature radiant chilled elements will reduce energy usage and limit radiant heat and/or provide additional radiant cooling and limit the comfort impact on a warming climate.
• When initially reviewing a building’s climate change risk profile, consideration of building loading is an early indicator of likely climate change risk exposure. Buildings that are externally loaded (i.e., the majority of their heat gains come from the building fabric, either because the floor plate is thin or because the space is sparsely occupied) are much more susceptible to the effects of climate change on comfort.

Construction – Although the effect of climate change on wind speeds and soil stability is not yet clear, we need to review our techniques, materials and fixings to ensure that new buildings are weatherproof and robust. (‘Design for Future Climate’, Bill Gething, page 20)

• UKCP09 provides average wind speed increases, but the real risk to building structure is peak wind. The team was able to determine what peak wind speeds would create a problem and provide that information as a trigger point for action, should peak wind speed data be available in future. Current U.K. design practice allows for a 50 percent increase in peak wind speed, demonstrating there is some wiggle room for extreme events.
• UKCP09 guidance suggests an increase in mean winter rainfall leading the team to typically suggest an elevation in the exposure category for wind driven rain intensity (using the Building Research Establishment scale).
• Lightning strikes per annum are expected to increase potentially changing a project’s risk category and the required lightning protection regime.
• Typically, temperature impacts on the performance of structural elements (e.g., increased thermal expansion) was found to be negligible. Likewise, the consequences of increased UV exposure on the performance and durability of exposed building elements was found to be insignificant since modern materials do usually have a good resistance to UV.

Water – With the prospect of summer droughts, more frequent extreme rainfall and increased flooding, water management is becoming a serious challenge for the building industry. (‘Design for Future Climate’, Bill Gething, page 30)

• In the U.K. as elsewhere, flood modelling for climate change scenarios is still generally subject to assumptions. Government guidance recommends designing stormwater attenuation assuming a 20-30 percent increase in the design rainfall event. A 20 percent increase is also generally used for river flows. Generally though, those allowances cannot reflect local variability and the science is still under development which makes it difficult to precisely quantify future flood risk and the appropriate level of future flood protection.
• The future availability of fresh water for building use is difficult to predict and affected by multiple variables including future population, technological improvement and behavioral change; combined with the current low cost of water this means that it is very difficult to demonstrate the financial viability of options like rainwater harvesting. More robust future water cost modeling would be a valuable addition to the cost-benefit analysis helping to promote the use of these initiatives, though existing water stress assessments along with general climate forecasts from UKCP09 do help to highlight geographically where water stress is likely in future.

In considering climate change adaptation decisions, conversations primarily focused on both uncertainty and impact of risk. Overall, the category with the most readily usable quantitative information - comfort - is perhaps the least important. Whereas issues of structural stability and flooding, which have general but not specific climate guidance, are potentially catastrophic if proper precautions or strategies are not implemented.

Conclusion

Expected changes in the climate over the next 100 years mean that we will need to adapt the design of our existing and new buildings to prepare them for the anticipated but as yet unknown extent of climate change impacts. By providing project specific advice considering building typology, location, climate and function, WSP | Parsons Brinckerhoff can prepare clients to tackle the challenges of climate change adaptation with the latest in climate forecast data and sensible risk mitigation techniques.

Part of the contract with the TSB was that the design for future climate activities, projects, and learning be disseminated to the industry externally as well as to peers internally. WSP | Parsons Brinckerhoff has provided a number of presentations and webinars, and contributed to a book and a documentary about the projects.

References

• ‘Design for Future Climate’, Bill Gething, Technology Strategy Board,
• Construction in a Changing Climate: Building for Resilience – a documentary produced by Climate South West in 2011 featuring Matthew Payne discussing the approach to climate change adaptation at Trowbridge County Hall
• Solutions Magazine June 2011 – The primary external PR magazine featuring Trowbridge County Hall
• Innovate ’11 – an event held by the TSB providing a cross section of innovation from multiple industries where Joshua Kates presented Great Ormond Street Hospital
• CIWEM Conference – the Chartered Institute of Water and Environmental Management event where Enrico Isnenghi presented specific water focus for Great Ormond Street Hospital.
• RIBA Design for Future Climate Book by Bill Gething - a book that summarises the first 26 projects in the D4FC competition that features WSP | Parsons Brinckerhoff’s work from Trowbridge and Great Ormond Street Hospital.

¹In August 2014 the Technology Strategy Board changed its name to Innovate U.K., to better express its role and purpose. Innovate U.K. is the U.K.’s innovation agency. It funds, supports and connects innovative British businesses through a unique mix of people and programmes to accelerate sustainable economic growth.

²http://www.metoffice.gov.uk/climatechange/science/monitoring/ukcp09/download/index.html

³http://emps.exeter.ac.uk/engineering/research/cee/

⁴ASHRAE (American Society of Heating, Refrigerating, and Air-Conditioning Engineers) is a global society advancing human well-being through sustainable technology for the built environment.

ASHRAE Standard 55 ( Thermal Environmental Conditions for Human Occupancy) is a standard that provides minimum requirements for acceptable thermal indoor environments.