Quantitative Assessment of Indoor Environmental Quality (IEQ) Parameters: A BREEAM-Based Evaluation Using Lux and Humidity Measurements in Residential Buildings

Indoor Environmental Quality (IEQ) is a critical component of sustainable residential building design, with daylight availability and indoor humidity regulation playing major roles in occupant comfort, health, and energy performance. Green building rating systems such as BREEAM, LEED, and IGBC assign significant credit weightage to these parameters; however, their requirements often differ in methodology, thresholds, and evaluation criteria. This study presents a comparative analysis of lux (daylight) and indoor relative humidity measurements obtained from a typical residential floor plan, assessed against the corresponding criteria in BREEAM’s Visual Comfort and Indoor Air Quality credits, and parallel provisions in LEED and IGBC. Field data were collected using calibrated lux meters and digital hygrometers across multiple functional spaces, including bedrooms, kitchen, living areas, and service rooms. The results reveal notable variations between measured conditions and rating system thresholds, highlighting areas of compliance, partial compliance, and deficiency. This research identifies the strengths and limitations of each rating system in evaluating daylight and humidity performance and proposes strategies for improving residential IEQ through design optimization and sensor-based monitoring. The findings contribute to a deeper understanding of how lux and humidity assessments can support effective sustainable building certification and enhance occupant well-being in residential environments.