The environmental value of buildings: a proposal for performance assessment with reference to the case of the tall office building

Abstract

Buildings consume approximately 33% of the world's energy, equivalent to 21% of global CO₂ emissions (IEA 2009, World energy outlook 2009, http://www.iea.org/weo/electricity.asp). Given the current scenario of energy consumption in buildings, the objective of this paper is to present some of the key issues related to assessment of the environmental performance of buildings, supported by the proposal of strategic indicators (with reference to the tall office building), followed by a critical review of the value of environmental design. Fieldwork has shown that a group of European case-studies show signs of change beginning to emerge considering value ahead of first cost, challenging the conventional commercial model. Energy savings and environmental quality in the operation of buildings bring marketability benefits to tenants, whilst future-proofing investments are of benefit to investors. In addition, buildings need to go beyond governmental targets to be able to remain competitive, adding value to environmentally considerate design.

Keywords:

• buildings
• environment
• quality
• value
• assessment
• criteria

Acknowledgements

Many thanks to Dr Neil Campbell, from BDSP Partnership, for providing the data on energy benchmarks of buildings in the UK and Germany.

Notes

1. The definitions of areas applied in the formulation of the indicators presented in category 1 follow those commonly used in the UK (Marmot and Eley 2000), based on the work of the Royal Institute of Chartered Surveyors.

2. For the diagnosis of the local climate and the calculation of outdoor thermal comfort, it is recommended that the Physiologically Equivalent Temperature index to be used (Höppe 1999).

3. Primary energy is the energy source; it measures not just the energy efficiency of the building itself but also the energy systems supplying it, whether they are local or remote. For example, in the case of gas-fired boilers, the owner would pay directly for the primary energy consumed. However, for grid electricity in Germany, the measurement from the meter is typically multiplied by three to account for the average efficiency of the power stations. Benchmarks can be measured on different area bases. For offices, figures can be normalized on gross external area, net internal area or metered area (permanently heated or cooled spaces) (CIBSE 2008).

4. Considering the comparative assessment of buildings in different climatic contexts with regards to the energy consumption of cooling and heating systems, once the figures are broken down according to different functions and end-uses, a second level of analysis is required. One option is to apply the concept of “degree days”, which establishes a common denominator for the comparison and avoids the influence of climatic differences in the comparative analysis of building performance. However, degree-days include only air temperatures and not the influence of humidity and solar radiation, which will have a key impact on the energy performance of buildings. A degree day is a measure of energy, in terms of heating or cooling. It is computed as the integral of a function of time that varies with temperature (typically, each day's temperature profile is treated as a sine wave with amplitude equal to the day's temperature variation, measured from maximum and minimum temperatures (Szokolay 2008).