A model for reducing energy consumption in existing office buildings: a case for Nigeria and United Kingdom building owners & facilities managers

The study investigated critical factors that affect office building energy performance in Nigeria compared to the UK; and developed an assessment and benchmarking framework for identifying appropriate operational, technical and behavioural solutions to improve energy performance of existing buildings. The mixed methods, multiple-case study approach was adopted for collecting energy used data from selected ten existing office buildings in both countries. A literature review was used to established worldwide view on factors influencing building energy performance. The selected factors were transformed into theoretical framework variables. These variables were further translated into an operational sustainability as an audit tool for establishing initial cases’ energy performance assessment. Operational energy data from case buildings were collected via: electricity bills, meter readings and fuels’ receipts/ invoices. Also, three online questionnaire surveys: a post occupancy evaluation for the assessment of comfort and energy performance of the ten buildings; a survey of facilities managers’ perception of managerial, operational and technical issues; and a model validation survey for confirmation of established factors from earlier two surveys, was employed. Likewise, a one-on-one semi-structured interview was utilised for owners/ managing directors and facilities managers of case buildings. Whilst, Structural equation modelling, analysis based on the validation survey, was employed to examine the dependencies and interdependencies of the critical factors. The IBM, SPSS 22 and AMOS 23 were used for the exploratory factor analysis and confirmatory factor analysis based on maximum likelihood estimations; which produced validated measurement and structural models. The study identified 52 critical factors that were transformed into 17 most critical factors impacting building energy performance in Nigeria and UK. The model identified new indicators for building energy performance; and established causality between building energy performance, management policy, operations and strategic driver as standard metrics for building energy efficiency assessment and benchmark. Likewise, it established a strong network of strategic drivers underpinned by strategic sustainability policy/ facilities management as mediator. The Nigeria buildings’ performance was found to depend largely on the context in which they operate in apart from the weather. Whereas, validity of climate variability as a critical factor of the UK case buildings’ energy performance was established. Institutionalised regulatory framework is suggested for Nigeria and sub-Saharan Africa countries as a control measure. The building energy performance model and its operational sustainability tool could be used as energy assessment and benchmark. It serves as a dashboard that encapsulates the energy efficiency performance and the absolute impacts of intervening factors. Finally, it presents insight into a critical path for intervention schemes as implemented; and the use of the strategic sustainability policy/ facilities management as mediation for improving building energy performance.