Towards a Brazilian standard for naturally ventilated buildings: guidelines for thermal and air movement acceptability

The Brazilian Federal Government has been recently promoting energy-conservation initiatives, most notably the 'Thermal Performance in Buildings - Brazilian Bioclimatic Zones and Building Guidelines for Low-Cost Housing' and the 'Federal Regulation for Voluntary Labelling of Energy Efficiency Levels in Commercial, Public and Service Buildings'. These new regulations provide information for designers based on Brazil's climate requirements, with specific advice related to lighting systems, HVAC and the thermal envelope of buildings. Nevertheless, requirements for naturally ventilated indoor environments appear as an open category without clear criteria. To address this, the paper proposes guidelines for naturally ventilated environments in which specific thermal and air movement acceptability goals must be achieved. The guidelines are based on results from field experiments in non-residential naturally ventilated buildings in different climatic zones as well as drawing on other studies. The proposed guidelines consider occupants' adaptive potential as well as thermal and air movement acceptability. Combining thermal acceptability with air movement acceptability is a key design challenge. Permissible operative temperature ranges are based on the ASHRAE 55 adaptive comfort standard, and minimum air velocity requirements within the occupied zone are specified. Considerations also included 'active' occupants and specific control over openings and fans.