Bessemer Grange Primary School – Children's Centre


Bessemer Grange Primary School

Project lead
Christian Dimbleby, Architype

Building type, sector and stage
Non-domestic new build, school, post-construction, school extension, in-use monitoring, Southwark

Primary school, natural ventilation, energy, lighting, controls

Timing of this summary

Two years after completion

The £2.4 million project is an extension to the 1950's Bessemer Grange Primary School in Southwark, South London. The extension provides facilities for a Foundation Centre (a nursery and reception) and a children's centre. The structure of the extension is of cross-laminated timber.

The building is naturally ventilated

through opening windows, roof lights and passive ventilation grilles. It is notable for having had a six-week Soft Landings residency by a member of Architype and the design team, who assisted the end users in settling into the building and teaching them how to operate it.

Bessemer Grange constructionEnergy performance
The Extension performs fairly well in terms of thermal comfort, and slightly better than the older building in terms of energy consumption. However, given that the Extension is a modern building designed to high standards, the energy consumption is significantly greater than predicted and is also well below the design ambition. Due to lack of sub-metering for gas in the new extension building, it is difficult to separate the energy consumption of the Children's Centre.
The energy data for 2011 portrays Bessemer Grange Primary School shows it performs better than the median values from the CIBSE TM 46 benchmarks (150 kWh/m2 gas and 40 kWh/m2 electricity) When the building is compared over the total logging period, it performs almost equivalent to CIBSE Guide F values for typical buildings. The extension building performs well in terms of the heating and gas consumption, but poorly in annual electricity consumption. It yet again confirms with the BPE team early analysis about the over-specified electrical equipment and lighting fixtures fitted in the extension building. 

Bessemer Grange energy performance

Above: Comparison of the Extension's energy performance against benchmarks.

Comfort issues
The Children's centre is designed for higher levels of controls than the existing main school, but its staff and teachers do not directly use these controls to modify indoor temperatures. If the temperatures are too hot or too cold, this is fed to the caretaker in form of a logbook maintained at the Children's Centre reception. The reception classroom on the ground floor has a difference in temperature of up to 2oC in the summer between itself and the spaces on the first floor. This the BPE team have previously identified is the result of the rooms on the first floor having limited access to control the ventilation, and the BPE team are working to resolve this.
Interviews with staff highlighted that the first floor spaces of the main school tends to get cold in winters while the children's centre had appropriate comfort levels. As both buildings are supplied from the same central heating system, it suggests a higher level of occupant control in the children's centre spaces compared with the main school. The staff complaints over overheating and stuffiness on the first floor during the summer months is backed by temperature data showing that the first floor is significantly warmer than those on the ground floor, especially in south west-facing rooms which are occupied only intermittently.

Bessemer Grange motorised windowsProblems have been observed in the operation of the high-level motorised windows. The physical appearance of the windows is such that a handle on the high level motorised section prompts people to use it to open the window. However, its function is supposed to be restricted to maintenance. It is mistaken for a normal handle as the switch for the motor (inset) is not intuitive to use. The BPE team intend to create a template to face the universal switch to make its purpose clear.