Exploring the Interconnection of Sleep Quality, Indoor Environmental Factors, and Energy Efficiency: Strategies for Sustainable Sleep Environments

This narrative review synthesizes interdisciplinary evidence on how indoor environmental factors, thermal conditions, lighting, noise, and air quality affect sleep quality and evaluates interventions to optimize these factors in energy-efficient buildings. We analyzed peer-reviewed studies (2000–2024) from Web of Science, ScienceDirect, PubMed, Scopus, and Wiley, selected through a structured screening process focusing on human studies in nonclinical settings. Evidence synthesis suggests that (1) moderate thermal environments, generally ranging between 18°C and 22°C, support sleep continuity in most healthy adults, though optimal thresholds may vary by age, region, and season. (2) Evening exposure to short-wavelength blue light, typically above 30–50 lux at 460–480 nm, disrupts circadian timing, particularly in adolescents and sensitive populations. (3) Nighttime noise levels above ~35 dB (A) are linked to rapid eye movement (REM) sleep disruption, with sensitivity varying by individual and noise source. (4) PM_2.5 and CO₂ accumulation in poorly ventilated bedrooms contribute to increased sleep fragmentation. Strategies like broadened HVAC setpoints and nighttime ventilation offer energy-saving potential without compromising sleep quality, but empirical support is sparse. Promising interventions, including dynamic lighting, acoustic insulation, and intelligent ventilation, need further validation in real-world settings. This review highlights the need for sleep-centric building standards and policies that prioritize both occupant health and energy efficiency. Future research should focus on personalized interventions and longitudinal studies to address mechanistic gaps.