Purpose: The purpose of this paper is to develop a set of affordable retrofit packages that can be applied to existing residential buildings in hot-humid regions to improve occupants’ thermal comfort and reduce energy consumption. Design/methodology/approach: A critical review of relevant literature to identify passive design strategies for improving thermal comfort and reducing energy consumption in hot-humid climates with focus on the building envelope was conducted in addition to a simulation study of an existing building typology in study area. Findings: There is enormous potential to reduce energy costs and improve thermal comfort through building retrofit packages which is a recent concept in developing countries, such as Nigeria. Analysing the results of the retrofit interventions using building energy simulation helped in developing affordable retrofit packages which had optimum effect in improving indoor comfort temperature to the neutral temperature specified for hot humid Nigeria and further down to 3°C less than that of the reference building used. The use of passive design strategies to retrofit the building might help homeowners reduce their annual energy consumption by up to 46.3 per cent just by improving the indoor thermal comfort. Originality/value: In addition to improving thermal comfort and reducing energy consumption, this research identified affordable retrofit packages and considered its cost implications especially to low-income earners who form a larger population of Lagos, Nigeria, as this was not considered by many previous researchers.

The production of conventional construction materials such as concrete, cement and bricks, has contributed significantly to the high environmental footprint associated with the construction industry. Moreover, there is a global push to deviate from the linear take-use-dispose model to a circular economy model, which incorporates upcycling and reuse of materials. This paper reviews the application of agricultural and plastic wastes, in construction, exploring the performance of the resulting component using five key parameters: compressive strength, tensile strength, flexural strength, density and thermal conductivity. The study showed that the compressive, tensile and flexural strengths can be increased slightly by increasing waste content; however, this only occurs in a narrow range after which an increase in waste content reduces the mechanical strength. This reduced strength can be attributed to a weaker bond resulting from the increased waste content. It also suggests that components may not directly benefit from the mechanical properties of waste materials. The waste materials resulted in a lower density which has implications for lightweight applications. Similarly, both waste materials were observed to improve the thermal insulation properties which is an advantage for improving thermal comfort in buildings. Despite the reduction in mechanical strength, it was observed that components with waste materials can be used for non-structural elements, thereby reducing the quantity and cost of new materials to be used. The application of these wastes in construction offers a pathway to reducing the environmental impact of construction, avoiding reliance on landfills for waste disposal and reducing construction costs. GRAPHICAL ABSTRACT

Operational building energy consumption accounts for 55% of global energy consumption. Most of this is attributed to residential buildings, as they make up the largest building type when compared to the total building stock worldwide. As the building envelope is a major contributor to building energy performance, especially the external walls, its optimisation is therefore imperative to reduce energy consumption and carbon emissions. This study set out to assess the effects of waste material additions to external walls and their effect on building energy performance. This research aimed to critically investigate the effect of rice husk ash (RHA) masonry blocks on building energy performance when compared to conventional masonry blocks in tropical climates. A mix of methods, including experimental investigation and simulation studies, were employed for this study. Three variations of RHA block samples were created for this investigation: RHA 5%, RHA 10%, and RHA 15%. Using prototype buildings from the study context, the building simulation results helped quantify the impact on building energy performance from the reuse of rice waste. The largest improvement to the building fabric was recorded with the RHA15% blocks, which resulted in a 9.9% and 11.3% reduction in solar heat gains through the external walls for the selected bungalow and duplex/storey building, respectively. This resulted in a 6.55% and 4.2% reduction in cooling loads and a 4.1% and 2.8% reduction in carbon emissions, respectively, for the bungalow and duplex/storey building. The findings of this research will prove valuable to householders, researchers, architects, and policymakers in their decision-making processes. The findings will also be useful in introducing new methods that can be adopted for similar studies, bridging the knowledge gap while promoting a circular economy through the reuse of landfilled waste.

Due to the effects of climate change, diminishing natural resources, and continuous urbanization, there is an increasing need for buildings to be more sustainable. This study explores the potential of upcycling plastic waste for the sustainable construction of low-cost homes in developing countries and contributes to filling the gap in existing studies regarding qualitative results of the in situ performance of buildings made from upcycled materials. This study compares the Bottle house with conventional buildings made of mud and cement. This study seeks to encourage the adoption of the bottle house concept for affordable housing by conducting a thermal comfort survey of its occupants. To obtain the thermal sensation vote (TSV) of the occupants, thermal comfort questionnaires were developed based on the seven-point ASHRAE thermal sensation scale. Additionally, a Testo 480 multifunction meter, which comprised an anemometer, radiant globe thermometer, air thermometer, and relative humidity probe, was used to calculate the predicted mean vote (PMV) concurrently. From the results of the TSV, mean votes of the participants of −2.0, 2.0, and 2.4 were observed for the bottle house, mud houses, and cement houses, respectively. In comparison, adjusted PMV mean values of 1.9, 2.1 and 2.1 were recorded for the bottle house, mud houses, and cement houses, respectively. The TSV and PMV results both indicate that the occupants of the bottle house felt more thermally comfortable when compared to occupants in the other dwellings. This can be attributed to the measures incorporated during the construction of the bottle house. Furthermore, the use of a simulation study helped proffer solutions to further improve the indoor temperatures of the buildings used in this study. The results of this paper will provide evidence of the prospects of upcycling plastic waste for construction and its impact on occupant’s thermal comfort when compared to conventional building materials.