The challenge of the performance gap faced by 201 Bishopsgate
One of the penultimate Green Sky Thinking events last week, was hosted by Henderson Global and British Land at their BREEAM Excellent 201 Bishopsgate office building.
The breakfast talk entitled ‘Occupying a BREEAM Excellent building: ensuring reality lives up to design’ looked at the challenges in overcoming the performance gap which they have faced on the building. Speakers included Justin Snoxall of British Land, Dave Worthington from Verco, and Fred Kinahan of Henderson Global.
British Land, the landlords for the Broadgate estate, within which 201 Bishopsgate sits, has set targets to reduce the carbon emissions of their building stock by 40 per cent by 2015.
201 Bishopsgate was completed in 2008, and was occupied in March 2009. The building achieved a 29 per cent better performance than that required by Part L. It was this building performance that was a key driver for Henderson Global agreeing to occupy the building. However, once they had moved in, they realised that it was not actually achieving this level of energy reduction.
Justin Snoxall says they found a number of environmental issues after the occupation of the building, including:
- Landlord metering was not integrated with occupier metering
- Energy consumption was greater than designed
Since realising that the metering was causing issues with how the energy efficiency of the building was monitored, British Land brought in a process integrating the metering across their whole portfolio on the Broadgate estate and this has been used to better manage the building efficiency.
Dave Worthington from sustainability consultancy Verco, was appointed to carry out post occupancy evaluation of the building. Funded by the Technology Strategy Board (TSB), the building has been monitored for two years. The TSB also provided them with additional funding to look into how out of hours energy use impacts on the performance gap.
Alongside assessing the performance of the building, the post occupancy evaluation also aims to answer the following questions:
- How energy efficient can a high spec, highly glazed building be?
- What are the effects of tenant engagement?
- How is energy consumed out of hours?
Worthington says, that from previous studies of buildings he has found ‘good buildings continue to get better and bad buildings continue to get worse’ which leads him to have a lot of hope for 201 Bishopsgate.
The final year of data collection ended in March 2013. Initial data is showing that the energy use for the building is very complicated.
‘There isn’t just one meter showing energy consumption for the whole building. This makes it very complex – especially to make sense of the data’, says Worthington.
‘IT consumption has gone up since the building was designed ten years ago, and this will also have an influence on the performance gap’, he adds.
After testing the façade it has been found to be performing better than designed. There is a lack of correlation between solar gain and energy consumption, showing it is what goes on inside the building which is affecting energy consumption rather than its design and construction.
Fred Kinahan from the building’s tenant Henderson Global, spoke about the building user surveys which have been conducted. These asked questions about the building, noise, comfort, lighting, the working environment, control over the internal environment of the building and the methods used to travel to work.
The building performed very well overall in these building user surveys. Overall comfort and satisfaction within the building was excellent. Where the building performance did fall down, was the internal air temperature – users reported that the building is too hot in summer and too cold during the winter, with temperature varying throughout the day. ‘This has highlighted that there is still work to be done on how the glazing and façade performs compared to how people feel within the building’ says Kinahan.
The talk gave details of both sides of the story – how those using the building actually feel, and the energy consumption of the building.
It was good to hear a developer open up about the fact that their building was not performing as expected, especially as part of Green Sky Thinking, where the ethos is to share and disseminate information on sustainable building practices. It is only if we really interrogate our buildings and look at their performance that we can address the issue of the performance gap.