Experimental investigation of light pipe and Window glazing retrofitting for improving indoor thermal conditions and daylight availability in existing buildings targeted for green retrofitting

Abstract

Abstract

Enhancing the indoor environmental quality of existing buildings is crucial for realizing energy-efficient and user-friendly built environments. Traditional structures are usually subject to excessive sunlight penetration through windows and a lack of adequate daylight, leading to greater reliance on artificial illumination and mechanical air conditioning. Passive retrofitting methods are a viable initiative for improving interior comfort without significant structural restructuring. This research presents an experimental study on two passive retrofitting methods: light pipe daylighting systems and retrofitting double-glazed windows with the goal of improving indoor thermal conditions and daylight availability in buildings. Selected experimental conditions were tested in a 3 m × 3 m × 3 m cube test chamber. Environmental parameters, such as indoor air temperature, relative humidity and illuminance were determined hourly between 09:00 and 16:00 h. The findings show that the indoor temperature dropped by 2 °C–3 °C with the retrofit of double-glazed windows. Additionally, the light pipe system increased indoor illumination by more than 520 lux on average compared to the usual 170 lux thus meeting the recommended indoor lighting standard. The daylighting retrofit also achieved approximately 62.5% reduction in artificial lighting energy consumption, while the glazing retrofit reduced indoor temperature by up to 3.2 °C, indicating lower cooling demand. The normalized TVCI was developed as an exploratory comparative index using the normalization of comfort scores with regard to indoor temperature, relative humidity, and illuminance as per the internationally accepted comfort ranges. The combination of light pipe and double-glazed windows gave the highest value of the normalized TVCI, showing the closest agreement with internationally recommended indoor environmental conditions in terms of thermal and daylighting comfort levels. It is clear from the results that the use of the combined retrofit method improves indoor environment efficiency and can possibly help to rely less on artificial lighting.