This paper presents some of the preliminary results from a study investigating the extent and causes of the discrepancies reported in the literature (e.g. [1], [2] and [3]) between computer-based predicted performance of buildings during design and their actual in-use performance using a number of case study buildings. A post-occupancy evaluation and performance assessment approach is used for the case studies in the form of measurement-based performance monitoring, user surveys, and the review of historical records of information from the design and construction phases of the projects considered. The project aims to provide a set of guidelines to be used by designers as decision support and by simulation tools developers to further improve the accuracy of their models in real life performance prediction. All the case studies in this research are school buildings designed and built in compliance with the most recent British and European building regulations (for example [4]). In order to meet the standards imposed by these regulations and minimise the consumption and pollution level from the new buildings, a number of new technologies have been used in these schools, some of them tried for the first time in a school building. In many cases, the inclusion of these new technologies means higher capital costs in the projects, which is not always affordable by public authorities, unless they are funded under the PFI scheme. Private Finance Initiatives (PFIs) are a form of public/private partnership introduced in the UK in 1992 where a private consortium provides the funding for the design and delivery of the project for a predefined re-payment scheme from the Government. PFIs are often (although not exclusively) used for the procurement of construction projects such as hospitals, roads and schools [5]. They usually involve a long-term commitment from the consortium to operate and maintain the buildings for a period of usually 15-30 years after construction, with the consortium paid back in instalments conditional on performance. On expiry of the contract, ownership of the project’s assets usually reverts back to the public sector. Therefore, a study on the divergence between predicted benefits of the aforementioned low carbon technologies and their actual performance needs to consider the role of all stakeholders including designers, builders, managers and users as well as relationships between and coordination among the four groups. This paper reports on findings concerning the impact of each of the main stages of a project’s life cycle and those involved in them on the overall performance of the case studies. The paper also emphasizes on the importance of communication and cooperation between the four stakeholder groups (at least for the first few years of the utilisation of the building) as a key to the success of the systems as designed. Evidence of under-utilised features or systems is presented and their potential effect on buildings performance is estimated.