Table 1 Indoor and outdoor temperatures at night and during the day

Type of roof Mean indoor temperature ( °C) Temp. difference ( °C) Temp. difference ( °C) p value
Indoors vs. outdoors From bare metal-roofed house
Night—1st part Bare metal 31.49 (31.19–31.79) 3.37 (2.13–3.60)
(21.00–00.00 h) Red 30.26 (29.96–30.57) 3.08 (2.80–3.36) − 1.23 (− 1.22 to − 1.23) < 0.001
White 29.75 (29.40–30.09) 2.51 (2.25–2.76) − 1.74 (− 1.70 to − 1.79) < 0.001
Night—2nd part Bare metal 29.43 (29.13–29.73) 3.41 (3.12–3.70)
(00.30–07.00 h) Red 28.42 (28.05–28.79) 2.78 (2.63–2.93) − 1.01 (− 0.94 to − 1.08) < 0.001
White 27.84 (27.43–28.25) 2.49 (2.26–2.72) − 1.59 (− 1.48 to − 1.70) < 0.001
Day Bare metal 33.98 (33.52–34.44) − 1.41 (− 1.71 to – 1.12)
(07:30–20.30 h) Red 34.42 (33.95–34.89) − 2.47 (− 3.13 to − 1.82) 0.44 (0.43–0.45) 0.081
White 33.05 (32.70–33.40) − 3.93 (− 4.75 to 3.11) − 0.93 (− 0.82 to − 1.04) < 0.001
Daily Bare metal 30.69 (30.31–31.06) 2.10 (1.63–2.58)
(00:00–23:30 h) Red 29.91 (29.48–30.33) 1.37 (0.97–1.77) − 0.63 (− 0.44 to − 0.82) 0.001
White 29.15 (28.71–29.58) 0.82 (0.21–1.43) − 1.44 (− 1.41 to − 1.46) < 0.001
1. Adjusted analysis for night, house position and number of coats of paint
2. Figures in parentheses are 95% confidence intervals
3. Data calculated with mean values for “night” and “daily”, and maximum values for “day” recorded and 95% CIs. General linearized modelling results adjusted for house position, roof typology, layers of paint and night