SOUTH LANARKSHIRE COLLEGE LOW CARBON TEACHING BUILDING TECHNICAL CASE STUDY

SOUTH LANARKSHIRE COLLEGE LOW CARBON TEACHING BUILDING TECHNICAL CASE STUDY

PROJECT INTRODUCTION 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. During the early stages of this project the Client worked with a project manager and a BREEAM assessor to develop the design brief. They carried out a full BREEAM Pre-Assessment, to establish what credits may or may not be available. This then became part of the design brief for the project. When the design team came on board we interrogated this 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.

DESIGN PROCESS Our first step in delivering a low energy design was to orientate the building to make beneficial use of solar gain and the prevailing wind but without the associated problems of glare, overheating and draughts. We sought to use natural ventilation as much as possible and this informed specific design elements e.g. the use of solar chimneys and stack ventilation through classrooms. Once the building orientation and layout had been agreed with the Client team we started to look at the building fabric. We have worked on many low energy designs and have several tried and tested methods that we can use to deliver our fabric first approach. For the ground floor, external walls and roofs we have developed constructions that give good thermal performance and airtightness but also have a high decrement delay (i.e. they heat up slowly) and can deal with moisture movement. We worked with Cundall, our project services engineer, to develop the design of the windows so that they would provide adequate daylighting and ventilation but without creating overheating problems. We had to adjust the design of Classroom 8, the first floor southernmost classroom, when the thermal model showed it potentially overheating. It now has a solar powered rooflight, which can be opened to provide stack ventilation directly to this classroom. Our services engineers produced two reports, for energy and overheating, that summarised the outputs from the energy model and identified key parameters that would be required for the building equipment and materials. These reports were then included as part of the tender documents and formed the basis of the services contractor s design. Along with the decision to use natural ventilation throughout the building, we sought to achieve good indoor air quality through the considered use of materials. We regularly use natural and recycled materials for their physical qualities and because they have a lower environmental impact that many commercial products. Before specifying internal finishes we checked that they had certification to confirm they had low VOC properties. This included the adhesives used to fix the floor finishes and all the internal paint finishes. The Client also checked that the furniture they were supplying also had low VOC properties. While we were on site, the plasterboard supplier also offered to upgrade the plasterboard to their new product that absorbs VOC s from the atmosphere, at no extra cost to the project. We are keen to monitor this over a number of years to find out if this product can deliver such an improvement in air quality. All materials specifications with specific environmental requirements were identified at tender stage and we emphasized that they had an impact on the BREEAM rating of the building. When the contractor offered alternatives they had to at least match the environmental standards of the originals. These alternatives were also checked with BRE to make sure that they met the credit requirements before any changes were agreed. Air quality testing was carried out prior to the building handover and showed that we had met our targets.

DESIGN FEATURES PASSIVE DESIGN Our site for this project is located on the south side of the existing campus. It was initially the location of the site cabins when the main College building was under construction. One of the gas mains for East Kilbride runs through the site, which affected the position of the building. 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/m 2 K, roof to be 0.12 W/m 2 K and ground floor to be 0.11 W/m 2 K; 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. It is crucial to the performance of the building that the internal vapour control membrane used to line the internal face of the external walls is an open permeable membrane, which allows vapour to come back into the building during certain climatic conditions and prevents vapour from getting trapped in the external wall construction. Although the natural ventilation design should deal with most of the potential moisture within the building, we were concerned that at certain times in the year, e.g. a wet, cold autumn or winter, would generate conditions where extra moisture within the indoor environment that could build up. Having breathing, or moisture diffusive walls, would give the building extra capacity to deal with the additional moisture and over a longer period of time. This, combined with the potential for night time cooling by using the actuated windows, give the building several different methods of controlling the indoor environment through passive methods rather than by using an air conditioning system.

ACTIVE DESIGN 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. The east facing classrooms work slightly differently, with openable windows on two sides to provide through ventilation. In addition, the top floor classroom also has a rooflight, which can provide stack ventilation on the hottest days. BRE is monitoring the performance of all these ventilation systems to find out how well they work in the current climate. RENEWABLE ENERGY Our Client has a lot of experience with renewable technology. They provide installation training for a range of technologies and have made use of them in both the main College building and the low energy test house they built a few years ago. 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. The heat from this system is passed through a buffer tank and is then used by the underfloor heating system throughout the building. The Client is now considering adding on additional components that will take heat from the building and pump it back into the ground on days when it is very hot inside the building. Not only will this help the cooling strategy but it also makes the use of the ground source heat pump more efficient. The Client team is going to wait until the results of the first year s post occupancy monitoring before making the decision to add to the system. 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. There is enough space on the remaining roofs for additional panels to be installed if the College require. 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. Ventilation Strategy Thermal Mass Strategy

OPTIONS FOR DIFFERENT CLASSROOM COMBINATIONS

SUSTAINABLE CONSTRUCTION From the outset of the project the Client team was very hands on. Not only had they recent experience of building the low energy test house on the site but their Construction curriculum staff work frequently with local contractors and students, keeping their own construction knowledge up to date. They asked a lot of questions as the design developed and were quick to point out where alternative solutions could be used. Once the project started on site they were keen to let students see things first hand. Along with these site visits, the Client employed Multivista, a photography company, to take regular site photographs at key points around the building. This digital archive covers the construction of every room and all services. It is possible to track how specific junctions were created through the timeline of photographs. This also proved useful to the construction team as the photographs were uploaded to the internet on a regular basis and allowed us to see things we might have missed on site. These photographs will be used as a teaching resource long after the construction is finished. Knowing that we were also going to go through a post completion BREEAM assessment gave us motivation to make sure we were checking up on the materials information to be obtained from the suppliers. Both we and the contractor gathered up environmental information prior to any orders being confirmed, so that we could make changes if this information was not available. We were also concerned that the as-built u-values of the constructions using specific manufacturer s information and the M&E equipment information might affect the as built energy model. Our services engineers ran another version of the model using construction information to confirm if the energy requirements had changed, which they had. This required that we use slightly more photovoltaic panels to achieve the net zero energy use target. As the project drew to a close the contractor arranged pre-testing inspections from the acoustic engineers and their air tightness testing advisor. These visits identified any potential weak spots which were addressed before the finishes were installed. As well as the acoustic and air tightness testing, thermal camera and air quality testing were also carried out prior to handover to make sure that the project had met all the criteria agreed with the Client. We have already started carrying out a post completion review on some of the project aspects. One of these was in relation to the potential site waste generated from the project. Our contractor, CCG (Scotland), had a robust site waste management process, with monthly audits of waste disposal, energy and water use. We worked with them from the outset to find ways of reducing any waste generated from the project. All the excavated material from the site was moved elsewhere on the campus. Any offcuts or end of palette stock on site was gifted to the College s construction department. Some suppliers offered a collection scheme for offcut materials as well. The Contractor was careful to order almost exactly the amount of materials required, which encouraged the workmen on site to be careful at installation stage. Any spare flooring and ceiling materials have been handed over to the Client for future maintenance use. Segregated skips were available on site at all time and in total only nine skips have been used. All the materials from these skips have been reused or recycled, so nothing has gone to landfill as a result of this project.

OCCUPANT FEEDBACK 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. It did initially feel as if the classrooms were cold if they were only half full. Fine tuning the CO 2 detection settings that control the ventilators has resolved this issue. 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.