Impacts of thermal adaptive behaviors in bedrooms on sleep quality and thermal comfort in the tropics

• Field measurements reveal sleep quality in tropical bedrooms in Indonesia. • Non-AC users maintain sleep efficiency with lower bedding insulation above 28 °C. • AC users below 26 °C experience increased cold-side discomfort after waking. • Sleep thermoregulation differs between tropical and temperate climates’ people. This study examined how thermal adaptive behaviors in bedrooms, specifically air conditioning (AC) use, adjustments of sleepwear and bedding insulation, affect sleep quality and thermal comfort in tropical climates. Field measurements were conducted in the bedrooms of undergraduate and graduate students in two cities with different tropical climates: Bandung (Af) and Surabaya (Aw), Indonesia. Participants were mainly classified into three groups based on AC use and outdoor climate conditions: (1) AC users in Surabaya, (2) non-AC users in Surabaya and (3) non-AC users in Bandung. The results revealed that sleepwear insulation did not significantly differ between the AC and Non-AC groups in Surabaya, but the bedding insulation was higher in the AC group. In the Non-AC group, at temperatures above 28 °C, sleep efficiency was ensured with lower bedding insulation. In the AC group, although indoor temperatures were maintained between 24.5 °C and 26 °C, sleep efficiency was lower than that of the Non-AC group with similar bedding insulation. In the AC group, higher sleep efficiency was associated with greater bedding insulation. Moreover, thermal discomfort with cold-side sensations increased after sleep in the AC group, particularly below 26 °C, whereas thermal discomfort was less pronounced in the Non-AC group. Between the two cities, the Non-AC groups showed no differences in sleep efficiency. These findings highlight the overlooked role of thermal adaptations during sleep in tropical climates and underscore the need for sustainable bedroom strategies to enhance sleep quality and comfort to counterbalance the increasing use of AC in this region.