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...met by a balanced mix of measures, with an emphasis placed on renewable energy and energy efficiency (DTI 2003).
A long-term strategy for reducing emissions involves replacing old and inefficient buildings with new low-carbon buildings, delivering equivalent or better levels of service. The process is driven by the Building Regulations (legal minimum standards required for all building work in the UK), which ensure flexibility in design, asking only for proof that the new building will perform significantly better than a "notional" building of the same size, shape, and function (ODPM 2006).
However, there is evidence that specifically designed low carbon buildings are consuming between two and three times more energy than predicted at the design stage (the prediction is often the calculation carried out for building regulations compliance). Bordass et al. (2001b) investigated the energy consumption of 16 "low-energy" buildings in the UK, finding a factor of 6 between the lowest and highest normalized [CO.sub.2] emissions (based on a unit floor area). The survey investigated a variety of building types; however, the most robust conclusions could be made by comparing the performance of the office buildings.
Energy targets are created through energy modeling software. While software and models are commonly calibrated and validated, studies often involve simple buildings, systems, and cells, such as Manz et al. (2006). Ahmad and Culp (2006) present results from a challenge to researchers to accurately model the energy consumption of four office buildings with known energy consumption. The researchers were given asbuilt drawings and allowed to survey the completed building for a total of 40 hours each but were not able see the actual consumption figures. The estimations of total energy consumption had an error in the range of [+ or -]30%. The error for individual end uses was in the range of [+ or -]90%.
Neymark et al. (2002) stated that two main types of errors prevail in energy models, internal and external errors. Internal errors take place at the simulation code level and in the simplification of the reality that is represented. This error is much discussed in the literature, and improvements have been shown to have been made by Neymark et al. (2002). The external error is related to the assumptions introduced by the software users; the following are common external errors:
* Differences between the actual microclimate and that used in the simulation
* Differences in schedules, control strategies, effects of occupant behavior, and effects from the building existing in the real world
* Differences between the actual thermal, optical, and other physical properties of the building, including its HVAC system, versus those input by the user
These external errors are likely to be made in the design process and can stem from a lack of understanding of how buildings are actually used by occupants and how the systems within them are controlled. This study investigates the design predictions using a simple energy calculation and concentrates on school buildings to enable comparisons to be made to design solutions.
In the UK, schools have traditionally been built in waves, with the Victorian stock being built shortly after the 1870 education act. The next major wave of school building took place in the 1950s and 1960s, following World War II and the 1944 education act, which raised the school leaving age to 15. The current government has now committed to modernize every secondary school (Grades 9-12) in the country due to the age of the existing stock and because of changing requirements, such as a greater emphasis on information technology (CfBT 2006).
New guidance to build schools has been published in an attempt to improve the quality of the stock. This guidance seeks to improve the acoustic performance (BB93 2003), thermal and visual environment (BB87 2004), ventilation (BB101 2005), and energy consumption (BB87 2004). Prescriptive minimum standards must be attained, leading to complex interactions between design intentions.
These guidance measures have profound consequences on the Mechanical Electrical and Public Health design and respective energy consumption. For example, before the onset of the standards, classroom ventilation was satisfied by large operable windows, which contributed to a large infiltration rate, and typically the space heating load was met by radiators. Today's acoustic standards for classrooms often prescribe windows that are too small to satisfy fresh air requirements. Also, the increased number of computers and lack of infiltration in modern schools have created a significant cooling load. A new approach is required to satisfy requirements.
This study evaluates schools built at the start of the current wave to assess how designers have tackled some of these new requirements in school buildings. The studies are post-occupancy evaluations (POE), which are defined as "an activity which originates out of an interest in how a building performs once it is built" (FFC 2003). POE has been used for a variety of reasons in the past, for example, to improve procurement practices for repeat clients (FFC 2003), to provide feedback to designers (Carmona 2004), or to give industry a picture of how buildings are performing (Bordass et al. 2001a).
Similar studies have been performed for other European buildings. For example, Santamouris et al. (2006) classified school buildings in Greece, with a view to assess the potential for improvement in the energy and internal environmental performance. The environmental organization ETSU (1980) reviewed over ten buildings to assess the potential for using passive solar heating in UK buildings and provided case studies to aid design decisions.
This study intends to complement the work of CART (2003) and Bordass et al. (2001b), provide realistic benchmarks for designers, and communicate general knowledge from post-construction evaluation.
METHODOLOGY
Five school buildings were selected for monitoring in this project, and to enable comparison, a number of criteria were set:
* Schools must have been completed between 2001 and 2005
* Schools must be secondary (high) schools (Grades 9- 12, children 11-16 years old
* Schools must be funded through the same program ("Academies" funding in this case)
* Gross floor area must be comparable (between...
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