Analysing Daylighting Sufficiency via Thermal Performance-Centred Glazed Fenestration in UK Residential Home-Office Environments

The COVID-19 pandemic has led to a rise in residential office utilisation. As a result, it has become increasingly important to configure workspaces and design dwellings to ensure adequate indoor environmental quality. Currently, UK industry best practice largely focuses on rationalising the window-to-wall ratio (WWR) for dwellings. However, there is an increased regulatory stringency on new build glazing thermal performance, without much regard to achieving adequate daylighting. This paper looks into enhancing daylighting sufficiency within newly constructed UK housing to meet the daylight availability requirements of the British Standard—BS EN 17037:2018+A1:2021—whilst simultaneously ensuring daylighting sufficiency, thermal comfort, and sustainability. A quantitative methodology was adopted using DesignBuilder through a calibrated daylighting simulation in association with thermal modelling for a typical semi-detached house in the UK. The performance of five glazing solutions with varying WWR was assessed against BS EN 17037:2018+A1:2021. The WWR of all glazing types was increased from an initial WWR of 15.26% until daylighting sufficiency was realised. The findings show that the house attained inadequate daylighting with the initial WWR of 15.26%, as 77% of frequently occupied spaces achieved an illuminance of 100 lx for 50% of the daylight hours and 300 lx for 42% of the frequently occupied space for 50% of the daylight hours, which failed to comply with the standard. Thus, a larger WWR of 25% is required for the house to comply with the current daylighting standard with the existing glazing type. However, a change of glazing type would enable compliance at a lower 20% WWR. In this study, a refinement strategy was conceived to review a combination of key parameters for refining the glazing selection. However, it was found that no compliant daylighting refinement strategy could be realised without an increase of 3.66 °C to the peak operative temperature. This paper, however, highlights the significance of fenestration selection beyond thermal performance, demonstrating the importance of other design variables such as daylight transmittance, solar heat gain coefficient, glazing heat losses, and peak operative temperatures.