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ASHRAE 62.1 standard Ventilation for Acceptable Indoor Air Quality, which is a LEED requirement, specifies minimum ventilation rates and other measures for the intent to provide acceptable air quality inside buildings.

The ASHRAE 62.1 standard is intended to be used by architects, engineers, manufacturers, contractors and operators. It sets minimum ventilation rates for all indoor spaces and for residential buildings of more than three stories. The standard has undergone many modifications since its first release in 1973.

First modification

The most significant modification was in the 2004 version, where the ventilation rate procedure had area-related and occupancy-related ventilation components Ra and Rp. The occupant component Rp is intended to dilute bio-effluents from occupants and other contaminants that result from direct occupant activities.

It is proportional to the number of people occupying the space. The building area-based component is intended to dilute sensory contaminants emitting from materials, furnishings and equipment within the space.

It is proportional to the occupiable floor area of the space. The ASHRAE 62.1-2004 rates are approximately 15% to 20% lower than the ASHRAE 62.1-2001 rates.

In the 2004 edition the indoor air humidity had to be fewer than 65% and pressure had to be positive when the space is being dehumidified.

The 2007 version requires special design for buildings that contain both environmental tobacco smoke and environmental tobacco smoke free areas, requires space classification based on the potential ETS presence in rooms, separation of ETS and ETS-free areas, and signage for ETS areas.

The 2007 standard prohibits recirculation of tobacco smoke to non-smoking areas, thus the ventilation rates provided in the standard are only for non-smoking areas. Smoking areas require no specific ventilation rates, but if existing, must have more ventilation and cleaning than non-smoking areas.

The 2007 version deletes the appendix for residential buildings and adds residential buildings ventilation and exhaust requirements to tables 6-1 and 6-4, corrects the inconsistencies in tables 5-2, 6-1, and 6-4 and provide additional information on several occupancy categories such as dwelling units and electrical equipment rooms.

Requirements

Both fresh air and exhaust air requirements for residential buildings have changed, the fresh air requirement used to be 0.35 Air changes per hour, now it has an area-related and occupancy-related ventilation components.

As for the exhaust, the kitchen continuous exhaust doubled from 25 cfm to 50 cfm and the bathroom changed from 20 cfm to 25 cfm. These increases in exhaust air will definitely raise the energy demand of HVAC systems in residential buildings.

As for the office buildings there are no significant changes between the 2004 and 2007 versions.

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