Table 2.

Studies on the effect of extreme heat on indoor thermal comfort.

Ref.	Sample Size/Location	Main Findings	Methods	Thermal Comfort Assessment	Factors Affecting Indoor Conditions
[42]	20 largest metropolitan areas in the US	Significant vulnerability to heat disasters with more than 50 million citizens at risk. Intensification of urban heat islands and climate change worsens the situation.	Whole-building energy simulations	Buildings exceed overheating threshold in 5–7 h on average in half of the simulated locations.	Construction practices, urban development, presence of AC, climate change
[43]	24 senior apartments, 3 public housing sites in NJ, USA	High exposures to overheating during summer. Indoor Heat Index exceeded thresholds of 27 °C. Overheating was higher in the 30s′ low-rise site.	Environmental and behavioural monitoring and interviews	Overheating and poor air quality, even with window opening.	Building age and presence of natural ventilation.
[44]	327 dwellings in New York City, NY, USA	Indoor temperatures are positively and strongly associated with outdoor temperature during the warm season. Apartment buildings and dwellings on higher floors are significantly warmer.	Temperature and humidity measurements	Not specifically addressed, but dwellings in higher socioeconomic status neighborhoods are significantly cooler.	Outdoor temperature, number of rooms in the dwelling, water damage, housing type and location
[45]	16 homes in Greater Boston, MA, USA	Correlation between indoor and outdoor temperatures only at warmer outdoor temperatures. Absolute humidity exhibited the strongest indoor-to-outdoor correlation.	Comparison of indoor and outdoor weather measurements	Not specifically addressed.	Outdoor temperature, apparent temperature, relative humidity, absolute humidity
[46]	145 homes in low-income households in Baltimore city	Large variation in indoor temperatures, with daily-mean indoor temperatures varying from 10 °C lower to 10 °C higher than outdoor temperatures. Houses with central AC are generally cooler than outdoors.	Temperature measurements	Not specifically addressed but noted large variability in indoor and outdoor temperatures.	Availability of AC, outdoor temperature
[47]	30 different homes in Detroit, MI.	Average maximum indoor temperature was 13.8 °C higher than average maximum outdoor temperature.	Hourly indoor temperature measurements, outdoor weather data	Indoor temperatures exceed the comfort range among elderly occupants.	Outdoor temperatures, housing and environmental characteristics
[48]	30 residences in northern Manhattan, NY	Indoor temperatures are far more stable than outdoor temperatures, with the indoor diurnal average typically above the outdoor average.	Sensor measurements, interviews, personal stories	Not specifically addressed.	Building interior thermal inertia