| Summary: | The common weighted scoring evaluation technique is presented by the design methods literature and by many practical guides as being an appropriate method for appraising different design solutions, however there are few critical assessments of the assumptions inherent in the method and no serious attempts to evaluate the validity of the technique as applied in a design context. This thesis presents a series of empirical studies and theoretical reviews which examine, in a logical sequence, aspects of the validity of weighted scoring techniques in the context of early stage heating, ventilating and air conditioning (HVAC) system design for office buildings. The nature of the HVAC design process is investigated, and in parallel with this a theoretical critique of the weighted scoring method as described in the design methods literature is conducted. It is found that the common approach to weighted scoring is invalid, raising concern over the indiscriminate use of such decision aids. However, a theoretically correct interpretation known as Multi-Attribute Value Theory (MAVT) is possible. It is also found that the method is not applicable to the selection of HVAC systems in general, but may be considered reasonably valid in more restricted tasks such as air conditioning system selection for a specific area in a building. While the MAVT models developed are judged to be reasonably valid, it is argued that their usefulness is debatable. If all the information on which to base the decision is available and the decision maker is reasonably skilled then MAVT will only improve decision making at the margin where the penalty for a wrong decision is less significant.
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