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Harris Academy, Purley

The aim of this project was to carry out research on a live construction project to evaluate climate change risks up to the end of the century and implement an adaptation strategy to address these risks. The architects of the project were Aedas, working alongside the mechanical engineers Van Zyl & de Villiers and contractors Willmott Dixon. The end user was the Harris Federation whose architectural brief included the refurbishment of an existing school building as well as the construction of new-build school blocks.

The research team joined the main project at the detail design stage with a brief to investigate practical recommendations for design adjustments that were cost and programme neutral. A range of impacts were investigated in the areas of thermal comfort, construction resilience and rain water management. The study built on recent research in occupant expectations, thermal modelling methodologies as well as the results of evaluations carried out for five schools as part of the TSB’s Building Performance Evaluation Programme.

Further project details

1. What approach did you take in assessing risks and identifying adaptation measures to mitigate the risks?

Thermal comfort was identified as a priority with particular emphasis on reducing the risk of overheating. The research team used the UKCIP02 ‘low carbon emissions’ scenarios to study how ‘minimal’ changes to external temperatures will impact on current design solutions. This approach was used to communicate to the client that should the building overheat under the ‘best case’ future scenario, it will likely overheat under all future climate predictions .

Existing solutions for natural ventilation were reviewed with the main design adaptation measures investigated including glazing performance, thermal mass and ‘ventilation free areas’

The research demonstrated that under future scenarios, when assessed against BB101 and BREEAM overheating criteria, individual design changes were unlikely to be sufficient in preventing overheating. Only a combination of all proposed adaptation options would meet the overheating criteria used to assess school buildings, even for the most optimistic future emissions scenarios.

2. How have you communicated the risks and recommendations with your client? What methods worked well?

The research team attended numerous design team workshops to understand the context of the project programme and made both formal and informal recommendations. The team also worked closely with the building services engineers to develop a research thermal model to allow the study to run in tandem with the contract work.

Using the most optimistic future emissions scenarios, a case was made for the recommended adaptation measures to be retained by the contractors as a minimum requirement. This approach may be suitable for other projects when entered at the detail design stage and where short-term financial priorities override long-term risks.

The impact of issues related to building management was also studied. Under future climate scenarios, these aspects will bear increasing importance alongside design adaptations. Furthermore, the researchers carried out interviews and surveyed the project team and the school’s pupils to gauge the views of designers and occupants on their subjective experience of overheating and views of various adaptation measures. This naturally extended to engagement with pupils and staff in the academy.

3.What tools have you used to assess overheating and flood risks?

Flood risks were not considered a risk item due to the geography of the site. The research team therefore focused primarily on overheating and used IES software to create a separate ‘research’ thermal model from the contractual thermal model. The model was used to test potential adaptation options under future climate scenarios.

4. What has the client agreed to implement as a result of your adaptation work?

The research team’s recommendations were only partially adopted, however, a significant improvement from the original design items to those procured was evidenced. Advice based on a predicted increase in rainfall levels and one in one hundred year storm scenarios directly influenced the size and number of rainwater outlets specified. Ventilation free areas were also improved.

The recommended increase of the high level top hung window opening distance to 400mm was adopted, whilst a 250 mm opening distance was ensured to the low level openable windows. Glazing g-values did not meet the recommended value of 0.32, however, were improved from 0.4 to 0.37 with no additional capital cost to the project.

Internal finishes moved from lightweight plasterboard construction to heavier density fibreboard but not to the recommended cementitious board.

The design team made a robust defense of maintaining the proposed floor to floor heights, which in theory would allow for the adoption of mechanical ventilation in the future. The argument was that a lower floor to floor height could render the building uncomfortable in 20 to 30 years, should ambient temperatures rise significantly within the design life of the building.

The team also looked at the way in which resilience issues were addressed by current design standards. In particular, the team analysed the sensitivity of the overheating results to unregulated energy use.

The impact of a range of internal gains and hampered night ventilation were studied. The results indicated that the impact of these are potentially greater than the improvements that can be achieved by the chosen adaptation measures. This highlighted the importance of considering climate change early on in the design process and agreeing on realistic modelling assumptions in both the current and future climates. The question remains whether a more robust analysis method that includes the impact of occupancy should be developed to ensure that buildings are more resilient to climate change.

Harris Academy, Purley

5. What were the major challenges so far in doing this adaptation work?

As the core research team was based within an architectural practice, a research thermal model of the building was required to be built as intellectual property rights prohibited the building services engineers from sharing their contractual thermal model. Adaptations and risks were tested in the research model before being simulated in the contract model by the building services engineers. While this process proved useful for the core research team in understanding the intricacies of the design adaptations, it was timely and required assistance from a simulation specialist. This highlights both the need for transparency of computational models within the industry and the need for custom simulation tools of reduced complexity that cater for the needs of architects.

Furthermore, the pressured programme and cost driven value process coupled with minimum briefing requirements set by design guidance and regulatory standards has made the adoption of some of the recommendations difficult.

6. What advice would you give others undertaking adaptation strategies?

This research commenced almost one year after outline proposals were submitted and part way through the detailing stages of the building procurement process. The limitations of joining the project at this later stage were that early design and briefing decisions could not be influenced. Early communication with the client, of the significance of future climate adaptations, is also important in order to fully incorporate an adaptation strategy into the contract and design workflow. It is therefore recommended that future climate adaptations studies begin at the briefing stages of a project. Nevertheless, this research has demonstrated that the basic design assumptions of a project can be re-assessed at the detailing stages and successfully integrated into a future climate adaptation strategy. Despite budget restraints, this has enabled critical features, such as the glazing specification and internal finishes, to be improved.

Primary benefit of the work has been to increase the overall awareness and understanding of this subject across the practice. The research was led by architects who worked closely with researchers from University College London (UCL), building services engineers VZDV and cost consultants Davis Langdon. A key lesson has been the value of such collaborations for live design projects and the need for issues such as climate change to be approached from a multi-disciplinary perspective.

This project has helped highlight how increased transparency with regards to product performance and modelling techniques can assist efficiencies within the build process. The importance of suitable occupant engagement, maintenance and management systems in providing robust buildings in use, moving into a future climate, has also been a key lesson.