SCHOOLS & EDUCATION FACILITIES SUPPLEMENT COLLEGE REFURBISHMENT
30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0
28/03/2011
Internal temperature (deg C) 30/03/2011
External temperature (C) 01/04/2011
High alarm 03/04/2011
Figure 1: Observed temperatures over a two-week period, showing improvements in user comfort after the refurbishment of the GE Fogg Building
live laboratories and a building which bridges a public highway, installing 4,600 sq m of rainscreen cladding and curtain walling across the complex building geometry.
We decided that if we opted for glazing with an improved solar thermal transmittance value, we could do away with shading fins and reduce the capital costs
Overheating and solar glare The team evaluated a range of solutions to reduce the heating and cooling demand, while maintaining suitable internal conditions for building users. After an analysis of the practical constraints – orientation and building configuration – and budget restrictions, FBM and Fulcrum decided on
a three-fold solution: l Increasing the insulation of the existing opaque walls;
l Installing new high-performance glazing throughout; and
l Including monocrystalline photovoltaic (PV) cells on parts of the south and south- east-facing sloped roofs.
‘We looked at a range of solutions including solar shading on the west façades,’ says Dabee. ‘We decided that if we opted for glazing with an improved solar thermal transmittance value, we could do away with shading fins and reduce the capital costs.’ Fulcrum provided environmental
modelling services and estimated that these measures would reduce the heating energy demand by 70%. The size of the replacement windows was carefully calculated to keep cost to a minimum whilst achieving the desired comfort levels internally, balancing heat gain with natural light and ventilation requirements. ‘We carried out a lot of calculations,
6 CIBSE Journal March 2012
supported by the thermal modelling, using Building Bulletin 101 for educational buildings and CIBSE guides to work out the required openable area for ventilation,’ explains Dabee. ‘Around 20% of the façade is openable.’ A slotted handle allows either trickle ventilation to Part F of the Building Regulations or wider opening in the summer months. BB101 allows for 28C temperatures in the summer. The improved thermal properties of the
building envelope have led to a significantly enhanced working environment for staff, students and visitors. Building users indicate significant improvement in terms of user comfort, with departmental managers reporting high levels of satisfaction.
Energy monitoring In terms of quantitative metrics, data loggers were placed in a third- and sixth-floor room following partial completion, to validate the design approach. Observed temperatures over a two-week period in April-May 2011 (post- completion) showed internal temperatures at a comfortable 20C, even when external temperatures fell to 4C (see Figure 1). Fulcrum’s thermal modelling and design
estimates predict a reduction in demand from 70,300 kWh/pa before refurbishment to 20,350 kWh/pa post-refurbishment, arising from improved efficiency of the building envelope (see Figure 2). The trend was validated by spot-checks on completion of each phase. The overcladding and improved insulation on the external walls have improved U-values
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Low alarm 05/04/2011
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