55. Notwithstanding section 51 and subject to the Regulation respecting the quality of the work environment (chapter S-2.1, r. 11), where the indoor winter design temperature is less than 18 ºC, the minimum thermal resistance R1 may be determined in accordance with the following formula:
R1 = ti - to
___________ • Rt
18 - to
ti = winter indoor design temperature (°C)
to = outdoor design temperature for heating purposes (°C)
Rt = thermal resistance required in section 51 or 52 (m2 • °C/W)
This section does not apply to residential occupancy buildings or to hospitals or aid centres.