"The amended Building Control Act requires all existing buildings with a gross floor area of 15,000 m2 or more to achieve the minimum Green Mark standard when they have undergone retrofitting. Audits are conducted every three years and companies have to submit energy consumption and energy-related building data."
(Source: Climate Action Tracker, June 2019, https://climateactiontracker.org/countries/singapore/current-policy-projections/)
This amended act supersedes the original Building Control Act (http://climatepolicydatabase.org/index.php/Building_Control_Act_(Chapter_29)_Singapore_1989).