ASSESSMENT OF LOW-ENERGY DESIGN STRATEGIES IN UNIVERSITY OFFICE BUILDINGS: CASE OF FEDERAL UNIVERSITY OF TECHNOLOGY, AKURE, NIGERIA

Abstract

Low-energy design strategy is a method of implementing passive features at early design stage to achieve an energy-efficient building that is capable of providing high standard of comfort with low energy consumption. Interest to invest in low-energy design strategies have grown especially because of the benefits of mitigation of climate change and achieving overall sustainable environment amongst others. Since buildings are responsible for a considerable proportion of global energy use that leads to negative impacts on the environment, adoption of low-energy strategies are of great benefits to reduce global energy consumption and the associated carbon emissions. The aim of this research is to assess low-energy design strategies in office buildings with a view to propose improvement strategies to reduce energy demand for thermal comfort. Mixed method of investigation was adopted, comprising of field experiment and questionnaire survey to gather data for the study. The experiment was scheduled during rainy and dry seasons of the year, collecting microclimatic variables of air temperatures and relative humidity in the three case office buildings. Structured questionnaires were administered during the period of the investigation to obtain information on the users’ perception of thermal comfort conditions in the case buildings. Methods of data analysis for the measured climatic variables included the use of R software to characterise and visualise thermal behaviour of the case office buildings throughout the period of the investigation; Rayman Model Software to compute Physiological Equivalent Temperature (PET) and Predicted Mean Vote (PMV) comfort indices; Computing the Temperature-Humidity (Thermo-Hygrometric) index. Methods of data analysis for the questionnaires included univariate analysis of all the variables under investigation, using descriptive statistics and bivariate analysis using Wilcoxon Rank Sum Test at 0.05 significant levels. Results from the field measurements showed that average values of indoor air temperatures and relative humidity during the rainy and dry seasons in the investigated office buildings were above comfortable indoor levels as specified by ASHRAE STANDARD-55 (2013) for summer, although, the case office building with more of low-energy strategies was more comfortable than the rest. Moreover, use of low-solar gain low-emissivity window glassing showed 89.54% improvement over ordinary single pane window glassing which is effective in reducing energy demand for thermal comfort. Results from the questionnaire administered showed that users perceived heat stress or hot discomfort during rainy and dry seasons within the interior of the investigated office buildings but that of rainy season is milder. The study concluded that lowenergy design strategies were not fully incorporated in office buildings within the study area, but use of strategies such as low-emissivity low-solar gain window glassing in existing office buildings improves indoor comfort conditions and reduce energy demand for thermal comfort. The study recommended that architects should consider and adopt low-energy design strategies in office buildings design for adequate energy savings and improved indoor thermal comfort conditions. Use of low-emissivity low solar gain window glassing should be incorporated into existing office buildings within the warm-humid climate of Nigeria.