BREEAM Outstanding South Lanarkshire College: A Case Study (by Catherine Cosgrove, Austin-Smith:Lord)
For this project our brief from South Lanarkshire College was a very simple one – to design a new eight classroom teaching building that achieved a BREEAM Outstanding rating. They asked that the design of the building echo the existing campus buildings, especially the main entrance.
The Client team wanted to ensure that the cutting edge curriculum taught in the College was incorporated into the design of the new building. They considered that first-hand experience being involved in every stage of the process to deliver a low energy building would inform how they teach their construction curriculum. They were keen to experience best practice sustainability design, including the use of locally sourced materials.
At the start of the BREEAM process we interrogated the brief thoroughly and carried out a series of consultation meetings with project stakeholders. In parallel to this consultation we carried out several surveys on the site to establish its key aspects, such as ecology, ground conditions, natural assets. The results informed our design process and refined our thoughts about a series of key decisions:
- Orientation of the building to make use of solar gain but preventing glare;
- Making beneficial use of the prevailing wind but also providing shelter from this wind;
- Using the building fabric to reduce the heating load required but also using thermal mass to help prevent internal overheating;
- Using natural air movement through the building rather than mechanical ventilation;
- Using low energy use equipment and fittings;
- Using a ground source heat pump and photovoltaic panels to offset the building’s energy use;
- Using rainwater harvesting, SUDS drainage and low water use fittings.
The design team discussed these options in detail and agreed that by using these criteria we stood the best chance of achieving a low energy building. Our focus was always on the long term use of the building rather than short term gains.
Our site for this project is located on the south side of the existing campus. Fortunately the orientation of this site was ideal to allow us to maximise the benefit of daylighting and natural ventilation strategies. We prepared a lot of function and massing diagrams to show the Client the benefits and problems of different layout strategies. From this process evolved an “L shaped” design with the main entrance facing back towards the main College building.
Having established the key design principles for the project we started looking at the building form in a lot of detail. While solar gain can be good in some cases, we felt that it might be a problem for the classrooms especially when so much of teaching now includes the use of electronic smartboards. We chose to locate the classrooms to the north and east sides of the building, with the main circulation corridor being located on the south side.
Our aim has been to provide a very simple passive design in which the main building construction elements will carry out most of the work in keeping the building comfortable to work in and easy to maintain. Our passive design strategy uses the following:
- Utilising solar gain from the south elevation;
- Fixed shading with timber louvres on south facing windows, to control glare and overheating;
- Thermal chimneys with louvres to the corridor side to provide air movement in warmer months of the year;
- Good daylighting level at every desk;
- Natural ventilation via openable windows in the north, east and west elevations, combined with stack ventilation in the corridors and atrium controlled by actuated windows at the top of both areas;
- Main entrance to face north, the opposite side to the prevailing wind;
- U-values of external walls to be 0.11 W/m2K, roof to be 0.12 W/m2K and ground floor to be 0.11 W/m2K;
- Open diffusive vapour control membranes in external walls and roofs, to allow any moisture within these constructions to migrate back into the building during certain climatic conditions;
- Vapour permeable natural fibre insulations in the external walls and roofs to allow them to “breathe”;
- Thermal mass of concrete composite floors and concrete blockwork in the main corridor walls;
- Good practice air tightness design details to seal construction junctions around the building;
- Low VOC finishes throughout the building.
The active design strategy uses the following:
- Actuated controlled windows in the atrium, corridors and top floor classrooms that can be opened wider to allow greater purge ventilation;
- Additional low level user operated windows to provide local ventilation in all classrooms, corridors and main entrance;
- A separate BMS system to control and monitor the rest of the building services;
- Underfloor heating using heat from a ground source heat pump;
- Local thermostat controls for all classroom heating;
- LED light fittings;
- Daylight and movement sensors on all lights;
- A low energy lift;
- User operated blinds to control glare from windows;
- Dual flush toilets;
- Flow restrictors on all taps;
- Leak detection on all incoming water supplies;
- A rainwater harvesting system.
Working with our services engineers, Cundall, we developed a strategy of using solar chimneys that draw warm air through the building via the stack effect. The north facing classrooms use openable windows to provide ventilation. Openable louvres at high level allows rising warm air to be drawn through to the corridor. As the thermal chimneys heat up, the speed of the rising air in the chimneys pulls air from the corridor via grilles, causing movement of air in the corridor and drawing air from the classrooms. Openable windows in the corridor also help to provide any necessary ventilation.
Our Client has a lot of experience with renewable technology as they provide installation training for a range of micro-renewables. They were able to advise us that the two ground source heat pumps they have already installed worked very well and were happy to use a third one at the new building. Along with the ground source heat pump we are using a photovoltaic array on the main roof of the building. This array should produce 120 pkW. Taken together, the energy generated by the ground source heat pump and the photovoltaic array balance out the electricity demand from the building, creating net zero energy use.
We have had a lot of good Client feedback since the building opened. Staff and students enjoy working in the building because it is so quiet inside. This is due to the thickly insulated walls, triple glazed windows and no mechanical ventilation. The sound insulation is so good that the building occupants can’t even hear the sound of the bus that stops outside the main classroom block.
The natural ventilation strategy is working well and the Client team is looking forward to the Spring and Summer months when the full potential of this strategy will be realised. Only one of the two ground source heat pumps has been required due to slightly milder winter temperatures than expected but this does show the heat in the ground has the potential to be used in a much larger building.
The Client Team have told us many times how much they enjoyed the project and how much they have learned about sustainable design. They have many plans to include the students in the ongoing monitoring of the building performance which will create even more knowledge about the building for their teaching curriculum.
This blog is an edited version of the full case study which can be found here:
South Lanarkshire College Case Study