Designing-in energy efficiency

Energy demand needs to be reduced to alleviate pressure on the security of the UK’s energy supply and to meet national and international carbon targets. The European Union set ‘20-20-20’ targets – a 20 per cent reduction in carbon emissions from 1990 levels; increasing energy generation from renewable sources by 20 per cent and a 20 per cent improvement in the EU’s energy efficiency – and it is expected that public sector buildings lead the way.

The Department of Communities and Local Government (DCLG) is also asking for zero carbon new non-domestic buildings from 2019. With so many targets to be met, energy prices rising and public sector spending under constant pressure, it is vital that schools particularly are made as efficient as possible to cut expenditure on energy bills.
    
The Chartered Institution of Building Services Engineers (CIBSE) has published new guidance to help estimate energy use from the design stage – ‘TM54: Evaluating operational energy performance of buildings at design stage’ and its Building Performance Awards showcases examples of best practice in school design and highlights the importance of post occupancy evaluation.

The Drawing Board
It is important for building designers and architects to take into account a sustainable and holistic approach to design. But engineers also need help with predicting the energy use of the building at the design stage and this is where TM54 can assist.
    
David Cheshire, Regional Director of Sustainability, AECOM and lead author of TM54 says: “TM54 can help you to establish how much energy your new building will use and therefore how much it will cost to run. It can also help to establish where the energy will be used in the building by breaking down the energy use into the different end uses. This can help to focus effort at the design stage when you’re looking at ways to make the building more efficient. When you’re operating the building, you use the TM54 breakdowns of energy use as a comparison with the data from the sub-meters to establish whether the building is operating according to the design intent.”

Different uses of energy in schools should be considered when estimating energy use, for example from basic heating and ventilating needs to those of cooking equipment, lighting and computers. The more information that is available on estimated use, for example  number of occupants and an estimate of time when power will be needed, the better. There will also be holiday periods where the energy use is dramatically reduced in educational buildings so it will perform differently from operational energy use patterns in an office building or leisure centre would, for example.

Exemplary Designs
By estimating energy use more precisely engineers can try and make the building run as efficiently as possible in order to reduce costs and carbon emissions. Some exemplary cases of well designed schools are the Preston Manor Primary School, Brent and Montgomery Primary School, Exeter. These are both shortlisted for the CIBSE Building Performance Awards 2014 ‘New Building Project of the Year (value up to £10 million)’ category. The Awards require effective demonstration of high levels of user satisfaction and comfort, measured building performance, energy efficiency and reduced carbon emissions.
    
HLM Architects designed the £6 million Preston Manor Primary School for 420 pupils with a green roof, solar panels, a skylight, natural ventilation, louvres and natural light available in every room. The school consists of 14 normal classrooms, a design and technology classroom, library, main hall and small hall. This project has been awarded a BREEAM Excellent rating, the Building Research Establishment’s Environmental Assessment Method, which provides a holistic approach to measuring and improving all types of new and existing buildings.
    
Paul Turpin, head of UK education at HLM, said: “This project is an example of what can be achieved in a tight timescale and shows that excellent environmental sustainability need not suffer during a fast-track process.
    
By looking at the project holistically, we were able to build in energy efficiency at the concept stage, during construction and over the life of the building. The BREEAM rating we have achieved recognises the value of this approach.”

Passivhaus
HamsonJPA, BAM, NP South West Architects and structural engineers Robson Liddle all worked on the Montgomery Primary School project in Exeter, for Devon County Council. This was the first Passivhaus school in the UK and the first zero carbon working school in Europe with site work completed in December 2011. Passivhaus is a standard focusing on dramatically reducing the need for heating and cooling whilst creating excellent indoor air quality. To adhere to the exact standards HamsonJPA’s sustainable design consultants and NPS Group’s design team worked closely with Devon County Council and the University of Exeter. In order to become zero carbon all energy had to be offset by renewable energy so solar photo-voltaic panels were installed and the Feed in Tarrif received from Ofgem in return will continue to benefit the school.

Finishing Touches
Projects entered in the CIBSE Building Performance Awards are judged by comprehensive data and their proven energy performance – not just a sustainable design and predicted energy use. It is the rigorous data collecting and post-occupancy evaluations that help get projects such as these shortlisted schools in the running for the Awards.
    
Dejan Mumovic, the editor of the forthcoming CIBSE Technical Memorandum on Integrated School Design and Senior Lecturer at the Bartlett School of Architecture at University College London highlights post-occupancy evaluations as a key factor when measuring energy of schools: “Design and operational issues are not unique to schools and are well known to engineers.”

Key principles he says that help to avoid energy-related problems include keeping design and control simple and fundamentally sound, and avoid overly complex systems.
    
Ensure systems are correctly commissioned and include post-occupancy evaluation.
    
Involve users throughout the design process, and ensure they are fully informed about how the building operates.
    
“Designers have to ensure that somebody takes responsibility for energy use and engages the whole school,” says Mumovic.

Post-occupancy evaluations help identify issues with systems after the building is handed over, how energy is being used and, perhaps most importantly, can help communication with end users. When staff know how to use systems or understand how the natural ventilation is supposed to work then they can improve the overall efficiency of the building by adhering to instructions. This is often referred to as a ‘soft landing’ approach where engineer and end users communicate to let the project reach its full potential. End user experience can be enhanced by allowing control of heating and lighting wherever possible which can improve occupant comfort and therefore productivity.
    
Another use for these checks is to compile data which can then be compared with the estimated use and then year on year on CarbonBuzz. This free to use RIBA CIBSE Platform allows data to be input and then compared with other buildings of its type as a benchmark. Sharing this knowledge and data will help energy estimations in the future become even more precise.
    
Adopting a holistic approach and communication during design, build and then after the building is handed over will benefit every property’s energy use. Reducing energy demand will alleviate pressure on energy supply and in the case of renewables such as solar panels these can provide repayments so are an intelligent investment towards zero‑carbon schools. CIBSE guidance can contribute to the design method and implementation of systems as well as estimation of energy in order to help lessen the gap between estimated energy use and actual energy use.

Further information
www.cibseknowledgeportal.co.uk
www.cibseawards.org