Circadian Effects of Daylight on the typical residential architecture of Tehran

This article examines the effects of residential plan design on the circadian rhythm through natural light in common residential spaces in Tehran over the past decade. Light profoundly influences human health, and home architecture plays a pivotal role in regulating the body's daily rhythms. Given that individuals spend a significant portion of their time indoors, especially during the transition from day to night, the levels of natural light throughout the day serve as a vital biological measure for human well-being at home.. The study delves into the importance of light's effect on melanopic cells in the brain and the human body's circadian rhythm, emphasizing the necessity to explore a brightness factor that accurately reflects vertically received melanopic light, akin to the movement of the human eye within indoor spaces. The first part of the study involved developing a theoretical framework for investigating dynamic daylight by explaining several related areas such as human perception and the psychology of light, light and circadian rhythm of the body, light evaluation criteria, light in architecture, typical residential architecture in Tehran. Subsequently,, employing logical reasoning methods and referring to the previous section, a theoretical framework was developed and a research model was obtained. After reviewing related research backgrounds, various simulation models for light movement in architectural spaces were used to collect basic information required for this section. In this study, initially, several variables regarding plan design were examined on simple plans and preliminary analyses were conducted on their effects on circadian rhythm during selected days from 9 am to 1 pm. After understanding these variables separately for examining residential spaces' effects, common house plans in Tehran were selected based on previous studies. Several plan samples were taken from specific building locations and modeled using Rhinoceros 3D software and ALFA plugin. Then melanopic lux levels were measured at numerous points on an assumed grid in four directions at each point throughout the entire unit's plan. Design recommendations for improving the performance of circadian rhythm synchronization of the body with the environmental circadian rhythm, for common plans in Tehran while considering municipal regulations and relevant restrictions were proposed. These includedeepening the interior space based on the direction of openings leads to a decrease in the desired spatial percentage. This issue is less problematic in southern facades but significantly reduces space desirability in northern facades. Therefore, deepening the space in northern facades is not recommended. Dividing and breaking down the dimensions of interior space leads to a decrease in receivedEquivalent Melanopic Lux . In houses with two-sided northern and southern facades, it is recommended that the living room faces south and bedrooms face north. In apartments with two units per floor, it is recommended to divide units into two units with two-sided northern and southern facades. In addition to computer software simulations, field measurements were taken at two sample houses on-site under similar conditions as those in the software to match results and confirm their accuracy. The results confirm the accuracy of output results from the software.