Abstract:
Thermal comfort in naturally ventilated buildings plays a crucial role in determining
indoor environmental quality. It directly affects occupant health, productivity,
and overall well-being, especially in warm-humid climates such as Sri Lanka
where buildings rely substantially on natural ventilation. This study investigates
the relative influence of environmental, building design, and occupant-related factors
on thermal comfort in naturally ventilated office buildings. Furthermore, it
examines associated Sick Building Syndrome (SBS) symptoms and perceived productivity
impacts. A mixed-methods approach was adopted. First, a large-scale
questionnaire survey of the general public (n = 375) was conducted to prioritize
thermal comfort factors using Relative Importance Index analysis. This was followed
by detailed occupant surveys in two naturally ventilated office buildings in
Galle, Sri Lanka: the Department of Buildings (n = 25) and the Road Development
Authority (n = 20), to assess actual indoor comfort conditions, health
symptoms, and perceived productivity. Thermal comfort was evaluated using the
Predicted Mean Vote (PMV) model, supported by statistical analysis of occupant
responses. Results of the first survey show that air temperature is the most
influential environmental factor for thermal comfort, followed by radiant temperature,
air velocity, and relative humidity. Key building design factors include room
size, building materials, and window size with their placement. Moreover, occupant
density, clothing level, and activity level are occupant-related factors that
significantly affect perceived comfort. Results of the second survey show both
buildings exhibited warmer-than-neutral conditions (PMV ≈ 1.1–1.2), comfort
levels between uncomfortable and neutral, and a high prevalence of SBS symptoms
(DoB = 72%, RDA = 50%). Occupants also reported notable impacts of
indoor environmental conditions on work performance, indicating an association
between thermal comfort and productivity, although causality cannot be conclusively
established. The findings highlight the need for targeted thermal comfort
improvements through optimized natural ventilation, improved building envelope
design, and occupant-centered control strategies to enhance health, comfort, and
productivity in naturally ventilated buildings in Sri Lanka and similar climatic
regions.
