Comment: Winds of change
Ashrae has updated its ventilation standards for indoor air quality
ASHRAE ventilation standards 62.1 and 62.2 have been for many years the standards followed in many parts of the world for acceptable indoor air quality in the built-environment.
The purpose of ASHRAE 62.1, the most referred to ASHRAE standard in the UAE, is:
• To specify minimum ventilation rates and other measures intended to provide indoor air quality that is acceptable to human occupants and that minimises adverse health effects.
• A regulatory application to new buildings, additions to existing buildings, and those changes to existing buildings that are identified in the body of the standard.
• To guide the improvement of indoor air quality in existing buildings.
Both Dubai and Abu Dhabi’s municipality require compliance with ASHRAE ventilation standards for all new buildings.
Historically and until 2015, the scope of Standard 62.1; entitled ‘The Ventilation for Indoor Air Quality Standard’, was all commercial and residential buildings except low-rise residential (three storeys and below). Standard 62.2 was the Ventilation and Acceptable Indoor Air Quality for low-rise residential buildings.
In the 2016 edition this has been changed. Residential buildings have been completely removed from 62.1’s scope. Standard 62.2 will be the reference used for all residential buildings whether low rise or high rise.
Currently none of the UAE municipalities have adopted the 2016 version of the standards. The 2007 versions of both 62.1 and 62.2 are the currently referred to ventilation standards in the UAE building regulations.
We will yet have to see if the new version will be adopted and what effects it would have on the construction industry once implemented.
But this change will impact the ventilation calculations that were used for high-rise residential buildings. For instance, toilets continuous exhaust used to be 25 CFM and now, since 62.2 now applies to high-rise residential buildings, 20 CFM is the new norm.
Kitchen ventilation used to be 50 CFM as per 62.1 2013 and now, as per 62.2 2016, a continuous airflow of 5 ACH should be exhausted from the kitchen. A 4m by 3m kitchen would require a continuous exhaust of almost 100 CFM, double the amount required in ASHRAE 62.1 2013. The bigger the kitchen the higher the required continuous exhaust will be.
Note that outside air requirements for residential buildings are normally driven by the exhaust, since most of the time the calculated exhaust value as per 62.2/62.1 is higher than the calculated outside air value.
To keep the building under pressurisation to combat infiltration, designers normally provide 10% extra outside air to the calculate exhaust flow. So generally, in residential buildings outside air, or fresh air as commonly known in the UAE, is calculated at 110% of the exhaust value that is in turn calculated to the standard requirement.
This will raise the ventilation system energy consumption especially in a climate like Dubai’s and Abu Dhabi’s. Buildings that have more studios and one bedrooms will be affected the most, compared to buildings where the majority of apartments are three bedrooms or more.
Other changes in ASHRAE 62.1 2016 include the following:
• The definition of environmental tobacco smoke (ETS) has been revised to include emissions from electronic smoking devices.
•Ventilation is allowed to be reduced to zero through the use of occupancy sensors (not through contaminant of CO² sensors) for spaces of selected occupancy types provided that the ventilation is restored to the standard required value whenever occupancy is detected.