What Is LEED? – Indoor Environmental Quality

This is the seventh post in a series on the LEED green building rating system. The first post provided an Introduction to LEED, the second looked at the Sustainable Sites credit category, the third at the Location and Transportation credits, the fourth at Water Efficiency, the fifth at the Energy and Atmosphere credits, and the sixth at Materials and Resources.



Indoor Environmental Quality

The quality of the air on the inside of a building is important to all the occupants, as it can contribute to illness and lack of productivity.  Increasing the amount of fresh air and using building materials and products without harmful chemicals can improve the air quality.  Also important is the connection between the occupants and the world outside.  Having access to views of the outside and providing natural lighting are important to occupant well-being.


Minimum Indoor Air Quality Performance

This is a required measure and must be performed in order for a project to be LEED certified.  Provide the required amount of outdoor air ventilation as per ASHRAE Standard 62.1-2010 or local requirement, whichever is more stringent.  Monitor actual outdoor air intake, signaling an alarm when it is +/- 15% of the required minimum.


Environmental Tobacco Smoke Control

This is a required measure and must be performed in order for a project to be LEED certified.  Prohibit smoking inside the building.  Prohibit smoking outside within 25 feet of entrances and exits, air intakes, and operable windows.  Residential projects may allow smoking outside in designated areas, and individual units must be weatherstripped and sealed to prevent smoke from transferring between units or into common areas.


Enhanced Indoor Air Quality Strategies

This credit is worth 1-2 points.  Install permanent entryway systems (mats, grilles, grates) that capture dirt and particulates and keep them from entering the building.  Prevent interior cross-contamination by providing separate air exhaust systems for areas in which potentially harmful chemicals are used (such as a janitor’s closet or copy room).  Air exhaust system must create a negative pressure area (create suction effect).  Outdoor air entry points shall have a filter with a MERV (minimum efficiency reporting value) rating of 13 or higher (measure of the size of particulates that are filtered).  Replace all filters after construction and before occupancy.


Low-Emitting Materials

This credit is worth 1-3 points.  Use materials with low VOC (volatile organic compounds) content.  There are different requirements for interior and exterior products and for different categories of products.  Product categories covered under this credit include: interior paints and coatings, adhesives, flooring, composite wood products, ceilings/walls/insulation, and furniture.  Depending on the number of categories in which the VOC content is maintained below the threshold, 1-3 points are awarded.  If not all products used on a project meet the requirement, a budget method may be used to show that overall VOC exposure is less than required.


Construction Indoor Air Quality Management Plan

This credit is worth 1 point.  Develop and implement an indoor air quality (IAQ) management plan for the construction and preoccupancy phases.  The plan must address the following: follow all recommendations from the Sheet Metal and Air Conditioning National Contractors Association’s (SMACNA) IAQ Guidelines for Occupied Buildings Under Construction, 2nd Edition, 2007; protect absorptive materials that are installed or stored on-site from moisture; if possible, do not use permanently installed HVAC equipment prior to occupancy, or if used during construction, provide filters with a MERV rating of at least 8 and change all filters prior to occupancy; and prohibit smoking inside the building and within 25 feet of entrances during construction.


Indoor Air Quality Assessment

This credit is worth 1-2 points.  After construction has been completed and the building has been completely cleaned, follow one of the two following procedures to perform a building flush-out: (1) Change all filtration media and perform a whole building flush-out using at least 14,000 cubic feet of outside air per gross square foot of floor area, keeping the temperature between 60-80 F and the relative humidity no higher than 60%; (2) If occupancy is desired before flush-out, furniture may be moved in after 3,500 cubic feet of outside air has been delivered for each gross square foot of floor area, keeping it between 60-80 F and the relative humidity under 60%; once occupied, flush-out must continue at 0.3 cubic foot per minute of outside air for each gross square foot of floor area, until at least 14,000 cubic feet of outside area have been circulated for each square foot of floor space.  These flush-out options are each worth 1 point.

Two points can be earned by having an independent testing company test air samples for chemicals and VOCs just prior to occupancy.  If any levels are above the required thresholds, take immediate steps to correct them, and have the air retested.  Continue until all levels are in the acceptable ranges.


Thermal Comfort

This credit is worth 1 point.  Design the HVAC system to meet the requirements for thermal comfort as determined by ASHRAE Standard 55-2010, ISO 7730:2010, CEN Standard EN 15251:2007, or local standards.  In addition, provide thermal controls for at least 50% of the individual occupant spaces and group controls for shared multi-occupant spaces.


Interior Lighting

This credit is worth 1-2 points.  Provide lighting controls to at least 90% of the individual occupant spaces and multizone controls for multi-occupant spaces.  Lighting controls must allow users to set at least three different lighting levels (on, off, midlevel).  This is worth 1 point.

Provide light fixtures and placement to meet at least four of the light quality measures, including the use of lamps with a CRI (color rendering index) of at least 80, use of lamps with an expected life of 24,000 hours or more, choosing reflective fabrics/surfaces for furniture, and choosing reflective surfaces for walls and ceilings.  This is worth 1 point.



This credit is worth 1-3 points.  Provide proof through computer modeling that regularly occupied individual occupant spaces are provided with natural daylighting that meets the following conditions: spatial daylight autonomy of 55-90%, annual sunlight exposure of no more than 10%, or that illuminance levels will be from 300-3,000 lux at 9 am and 3 pm on a clear day at the equinox.  Credits are awarded based on what modeling process is used and the percentage of the floor space that meets the requirements.


Quality Views

This credit is worth 1 point.  Provide a line of sight to the outdoors for at least 75% of regularly occupied occupant spaces.  Views must meet requirements for multiple lines of sight, the subject of the view, the quality of the view, and whether the view is unobstructed.  Interior atria can be used to meet up to 30% of view requirement.


Acoustic Performance

This credit is worth 1 point.  Meet requirements for HVAC background noise, sound isolation, reverberation time, and sound reinforcing and masking.  Required levels vary according to the type of project and specific room type requirements.


Next, we will be wrapping things up with the Innovation and Regional Priority credit categories.


Primary Source: LEED v4 for Building Design and Construction (Updated July 1, 2014).