Over the duration of five consecutive school commissions from Wolverhampton City Council, the practice embarked on a pioneering journey to deliver Passivhaus to the education sector, working closely with Passivhaus expert, Nick Grant of Elemental Solutions. The series of schemes have been widely documented as exemplar projects and have been the focus of much interest from sustainable practitioners industry-wide, demonstrating the scope, affordability and long-term benefits of the standard.
Through an insightful and thorough research programme initiated by Architype, in collaboration with Coventry and Wolverhampton Universities, the practice has exposed energy performance and user comfort of the schools through a range of monitoring methods, as well as indicating important lessons learned which have consequently impacted on improving results with each consecutive school.
Exposing the truths
The research programme started in spring 2014 and has since been monitoring the thermal comfort, energy performance and user satisfaction of six occupied schools.
In the mix are two pre-Passivhaus schools by Architype, St. Luke’s Primary School, completed in 2009 and the Willows School, completed in 2011. Although not designed to Passivhaus requirements, the schools trialed a passive approach; designed to take advantage of the key principles of the standard, such as natural daylight, ventilation and robust insulation, as well as combining environmental strategies to achieve BREEAM accreditation.
The second batch of case studies includes Oak Meadow Primary School and Bushbury Hill Primary School. Both very similar in brief, they were completed in 2011, and as well as being Architype’s first generation of Passivhaus schools, they are amongst the first Passivhaus schools to be certified in the UK.
The final Architype school to be monitored is a second generation school, Wilkinson Primary School, completed early 2014. A product of collaborative working and lessons learned, the school has become a key indicator for the possibilities of the standard when applied confidently and followed by rigorous aftercare.
For added interest, a standard school, not designed by Architype, built to UK Building Regulations in the 1970s was also monitored under the same circumstances, with a view to highlighting the benefits of sustainable design versus designing to standard UK Building Regulations.
In the first instance, annual energy usage was gathered from each school using meter readings. These were measured against CIBSE (Chartered Institute of Building Services Engineers) national benchmarks; typical, good practice and the TM46 median. The results show that even the early, pre-passivhaus schools are well below the TM46 median, with only the additional energy from the biomass boilers taking the results slightly above the good practice benchmark. As for the certified Passivhaus schools, these are seen to be well below half of the good practice indicator, with the second generation school, Wilkinson Primary experiencing a 93% reduction in energy consumption compared with the TM46 benchmark.
Also measured in the study were the temperature and CO2 concentration of classrooms. These are important indicators because they reflect directly upon the wellbeing and comfort of users, affecting their health and alertness. Control classrooms of similar orientation and size were cited in each school and monitored over the course of a year. The results take examples from a typical week during winter and summer months.
Designing schools to perform well in the winter is an important and challenging task for the UK, maintaining comfortable temperatures in classrooms for learning, whilst keeping spaces fresh and ventilated to prevent stuffiness from high CO2 levels.
Graph 1 – Internal Temperature During Winter
Graph 1 shows the internal temperature of the control classroom for one week during the winter. The red line shown at 21°C, is the lower limit for learning, and the grey vertical bars indicate the occupied hours of classrooms. As you can see from the graph, the Passivhaus schools, Bushbury Hill and Wilkinson Primary School begin each school day at this level, rising to a comfortable and consistent 23°C, compared to the conventional 1970s school, which never reaches the lower limit during the typical winter week. Although the pre-passivhaus school, St. Luke's, performs significantly better than the standard school, there is still lots of fluctuation from daytime to night-time, which was rectified in the following schools.
Graph 2 – Internal CO2 Content During Winter
Graph 2 shows the CO2 content of the control classroom for the same week during the winter. The red line shown at 5000 particles per million (ppm) is the maximum peak for CO2 content in classrooms, with the grey line at 1500ppm, the upper limit for daily average during occupied hours, as set by the Building Bulletin 101.
The winter is the most difficult time to control CO2 levels because people do not want to open windows in the cold weather, so the air becomes stagnated very quickly. As you can see from the graph, the conventional school cannot control the CO2, and even exceeds the recommended maximum, with Wilkinson Primary School remaining consistently below the average line the entire week.
During the summer months, CO2 tends to be less of an issue, with users naturally ventilating classrooms by opening windows. Over heating risks are a growing issue due to a warming climate and more frequent hot spells.
Graph 3 – Internal Temperature During Summer
Graph 3 shows the internal temperature of the control classroom for a typical week during the summer. The red line at 22°C shows ideal temperature, with the comfort zone approximately 1 or 2° either side of this. The second generation Passivhaus School, Wilkinson Primary School, again shows the best results, consistently remaining close to the comfort line. Although the pre-Passivhaus school and first generation Passivhaus school are more consistent, they still average a little higher than would be ideal, but not to the extent of the conventional school, which accelerates to uncomfortably high peaks toward the end of the day.
Graph 4 – Internal CO2 Content During Summer
Graph 4 shows the CO2 content of the control classroom for the same week during the summer. Again, the red line shown at 5000 particles per million (ppm) is the maximum peak for CO2 content in classrooms, with the grey line at 1500ppm, the upper limit for daily average during occupied hours, as set by the Building Bulletin 101. Whilst the conventional school manages to control the CO2 content much better than in the winter, the Passivhaus and pre-Passivhaus schools still perform the best, with a mixed mode ventilation strategy.
Disseminating lessons learned
The research presented is some of the best in the industry in proving the worth of sustainable architecture and in particular Passivhaus in occupation. The ongoing results of the research have been disseminated to the industry, at various industry conferences, including the UK Passivhaus Conference, RIBA Research Symposium 2015, CIBSE Symposium and Architype’s programme of UK seminars in 2015. Besides offering evidence into how Passivhaus performs differently, another key aim of dissemination is promoting the lessons learned from the series of schools.
The study helped highlight the challenges and issues encountered in designing, constructing and occupying the first non-domestic Passivhaus buildings in the UK, and review how these issues have been systematically addressed to improve and optimise the design of subsequent buildings. These included improvements in construction detailing, addressing differences between Internal Heat gains (IHG) in Germany and the UK, optimisation of window design, rationalisation of ventilation systems, reductions in heating systems, simplification of controls and development of effective user manuals and support.
Schools of the future
Keen to build upon the ever-improving results, Architype’s latest project, Hackbridge Primary School, is a highly ambitious design which combines the Passivhaus standard with a Zero Carbon approach. The strategy aims to radically reduce carbon emissions, cut waste and provide a long-term sustainable approach that supports the local community.
The zero carbon aspirations will further support the fabric first approach with a range of low-carbon materials, supported by an extensive array or renewable energy, such as photovoltaic tiles and ground source heat pumps.
Planning permission has been granted for the 2FE scheme, and Phase 1 is currently undergoing detailed design with Architype, in collaboration with London Borough of Sutton.