CASE STUDY COSTA ECO-POD TAKING THE GRIND OUT OF PROCUREMENT Collaboration between landlord and tenant was essential in creating Costas first zero energy coffee shop. AlexSmith finds out how open minds and an enlightened design team redefined how the coffee chain procures its stores A new Costa outlet in Telford is causing a stir, with owners Whitbread claiming it is Britains first zero energy coffee shop. This may be difficult to substantiate no operational data is yet available but onpaper (and in dynamic simulations) thedesign appears to offer substantial energy savings. The building form of the concept store called the eco-pod is based on passive design principles. An overhanging, curved timber roof shades the large windows, so solar gain is minimised, while the soft-wood faade is highly insulated to keep interiors warm in the winter and cool in the summer. Passive ventilation from Breathing Buildings ensures the energy used to power fans is kept to a minimum, and underfloor heating and cooling provided by a ground source heat pump provides stable temperatures. (See panel, An integrated design, below.) While the low-energy credentials, which include rainwater harvesting, are impressive,the procurement method is even more so. The landlord and tenant were involved in design decisions before the lease was signed, which is highly unusual. The unit, at Wrekin Retail Park, is leased by Costa from the landlord, Hammerson. Usually, tenants are provided with a shell unit, which they fit out with services using their own project teams. As a result, the team working on the retail unit have no idea how the building is going to consume energy, so the design could be unsuitable for the buildings end use. This coffee shop is different. Costa and Hammerson discussed designs that would meet the retailers requirements before any contracts were signed. Collaboration was essential because Hammerson needed to know what energy savings would be made so it could set a rent that would allow it to recoup its investment from PVs and other low-energy measures. We are getting the savings in energy bills and they are getting the return on investment, explains Oliver Rosevear, energy and environment manager at Whitbread. There needs to be an understanding about the energy that will be saved before we agree to pay an enhanced rent. The low-energy design was brought to Costa by architect Emission Zero and project manager Projex. Simon Kirton, Emission Zeros architectural director, said it was essential to consider mechanical services at the shell design stage to estimate energy use accurately. Services have to be considered as part of the holistic design process. The fabric has so much influence on the way the building is serviced they cant be designed separately, he says. Unusually for an architect, Emission Zero uses dynamic thermal modelling to help it understand how different criteria affect the energy performance of a building. To predict the new coffee shops energy use, Emission Zero was given access to half-hourly data from three Costa stores. We were considering natural ventilation and passive floor slabs, and their accurate specification An integrated design Costas concept store is dependent on components working together effectively. Its control system, designed by Breathing Buildings, integrates the ventilation system with the underfloor heating and cooling (linked to a ground source heat pump), and supplementary air conditioning. Breathing Buildings supplied three internal mixing e-stacks and three mushroom terminations, as well as glazed-in dampers. The ventilation system works in one of two modes: displacement ventilation in summer and mixing ventilation in winter. In summer, perimenter vents at a low level provide incoming air, while roof vents exhaust warm air. The nighttime purge to cool the building is timed to happen between 8pm and 6am. When external temperatures are greater than 18C there is floor slab cooling. When they reach 23C, the ventilation is closed down and cooling is supplied by a supplementary split air conditioning unit. In winter perimeter vents at low level are closed, while roof vents bring in pre-heated fresh cool air . The night time purge is not operated. The floor slab heating turns on when internal temperatures fall below 17C. Low level dampers e-stack S-1200 unit e-stack S-1200 unit ToC Ext Heating interlock- 24V AC Volt free contact located inside e-stack control panel. Heating to energise relay coil when heating ON e-stack control panel located on wall o TC +CO2 o TC +CO2 Control switches Cable from heating controller Underfloor slab heating and cooling system linked to ground source heat pump A/C interlock Volt free contact Relay coil energised by Breathing Buildings and located inside e-stack control panel. Only used when internal temperatures exceed threshold value Cable from VFR A/C control A/C unit PROJECT TEAM Landlord: Hammerson Tenant: Costa (owned by Whitbread) Architect: Emission Zero Project and cost management: Projex Building Solutions Building frame design and build: Fordingbridge Ventilation: Breathing Buildings Rainwater capture Solar panels Underfloor heating Super-insulated faade Passive ventilation Sustainable timber frame Costas eco-pod in Telford - the UKs first zero energy coffee shop effect of a change onperformance in the specification of the glazing. Having a quantity surveyor (QS) who understands low-energy buildings is essential, says Kirton. Typically, low carbon projects start out wonderfully, but when it gets down to thenitty gritty at the value-engineering stage vital specifications get changed because the QS often has no idea of the impact their decisions have on performance. Conclusion Rosevear says the green lease arrangement with Hammerson has enabled them to incorporate lowenergy features, such as PVs, for the first time on a leased Costa store. He says that the PVs are making a significant contribution to the 50% lower energy use compared with a typical Costa store. The Telford store is now being eadE RMOR PROJECT TEAM was dependent on energy profiles of the building. Knowledge of the heat gains was crucial, and access to energy data enabled us to see exactly what was used and when, in any season, says Kirton. The data enabled Kirton to identify areas of high energy use. For example, the profile of convection ovens was very high; when Kirton investigated, it found that staff were turning on the ovens at the start of the day and not switching them off until they left. Looking at the energy profiles of various appliances gave Emission Zero the idea for capturing heat from fridge condenser units, to prevent it from being recirculated in the store. To minimise the heat gains, Kirton designed a cowl for the fridges that exhausted the warm air out of the building. The design process involved all relevant parties, including Hammerson, Costa and the specialist subcontractors, such as Breathing Buildings, which designed the natural ventilation system. Kirton described it as an iterative process: It takes longer to work through, but these iterations allow everyone to have knowledge of the process. For example, wecan look at the monitored and, depending on results, Costa will roll out the design both on more Hammerson retail parks, and with other landlords prepared to work with the same lease model. After four months, Kirton claims the store is performing as the models suggested. As the building is still being monitored, the controls can be altered to account for the change in seasons, when the slab requires less nighttime purging. Kirton says the store should continue to be monitored for performance. He is keen for more landlords and tenants to discuss building requirements and is exasperated that it isnt happenning more. I find it quite shocking that nobody has done this before. It should be joined-up thinking, but sadly its not the case, he says. At the moment, the building gets designed, and then the engineers look at it too late in the process. Rosevear believes the collaborative approach between all the partners broke down barriers: Tenants and landlords tend to work for themselves but this approach had to be open book. CJ