The word green conjures images of a lush, vibrant ecosystem that is full of healthy living things and fresh air. Green buildings are typically thought of as those that use minimal resources to construct and operate and cause as little negative environmental impact as possible. Though providing for an indoor environment that attempts to mimic an ideal ecosystem is typically a part of green buildings, it is not always achieved. 

During the 1970s energy crisis, the trend was to seal up buildings (e.g., no more openable windows and more airtight envelopes) and reduce outdoor air intake to save energy. This contributed to what was termed “sick building syndrome” or “tight building syndrome.” It seems that some of those mistakes of the past are being repeated.

The U.S. Green Building Council’s LEED rating system has been steadily deemphasizing indoor environmental quality (IEQ) and emphasizing energy savings. This was made obvious during the LEED 2009 for new construction changes, which took the IEQ Category from having 21.7% (second most) of the available points to 13.6% (barely the third most) while increasing the energy category from 24.6% to 31.8%. These percentages have remained similar in the new LEED version 4. The only IEQ aspects of LEED for new construction that are required are controlling environmental tobacco smoke and providing the ASHRAE minimum amount of outdoor air. This approach is closely repeated in similar rating systems, codes, and standards.

Several studies of the lifetime return on investment (ROI) from green buildings have shown that the increased productivity and reduced absenteeism (IPRA) benefits far outweigh any others. A study titled “Green Buildings and Productivity” (Miller et al., 2009) indicated that IPRA returns many times more on ROI than typical energy savings. IPRA is mostly associated with the improved IEQ that properly built green buildings typically provide. Though IPRA is not as easily quantified as energy savings, it must be considered when prioritizing which areas to emphasize. This makes it obvious that the IEQ category of LEED and other rating systems, codes, and standards should be emphasized rather than deemphasized.

Twenty Reasons for Indoor Air Quality (IAQ) Problems

At this point, the twenty reasons that can negatively impact IAQ will be discussed. It should be noted that IAQ is a subset of IEQ. Non air-related issues such as ergonomics, lighting, noise, etc., will not be discussed in this article, although they are very important topics. The following discussion is simply illustrative and based on the author’s 27-plus years of experience in diagnosing and treating IAQ problems. They do not include all the issues that may negatively affect IAQ.


1. Non-Cleanable Interior Ventilation Surfaces

Large air conveyance ducts and fan-coil housings are often lined on their interiors with coated fiberglass materials. The purpose of the lining is typically noise reduction and heat transfer reduction. The problem with this lining is that it can eventually degrade which can lead to fibers and particles being emitted into the occupied spaces causing health concerns. In addition, the lining can become a reservoir for dust accumulation and cannot be adequately cleaned using currently available techniques. The dust that can accumulate can also provide the nutrients needed for mold growth if the lining material becomes wet or damp.

2. Too Much Outdoor Air

One trend in green buildings is to increase the amount of outdoor air brought in. The concept of “the more the better” prevails. However, the old adage of “everything in moderation” better applies in this case, especially when the outdoor air is very dry.

When the indoor air of a building is not recirculated or is very minimal (e.g., 100% or near 100% outdoor air) and the outdoor air has very low relative humidity (e.g., less than 20%), it can cause abnormally low humidity in the occupied space, which can lead to a variety of adverse health effects. Allergic-like symptoms such as eye, nose, and respiratory tract irritation; congestion; and sneezing can be associated with excessively dry air. Also, studies (e.g., “Influenza Virus Transmission Is Dependent on Relative Humidity and Temperature,” Lowen et al., 2007) have indicated that viral infections spread more easily through the air in dry environments than in humid.

3. Cellulose Materials in High Water Use Areas

Cellulose containing materials in high water use areas such as bathrooms (especially around showers), janitor’s closets, and kitchens serve as “mold food” if these materials get wet or damp. The most common source of cellulose leading to mold growth is the paper on drywall. Other important cellulose sources include wallpaper adhesives and some carpet backing (e.g., jute or other plant-derived backings), especially when they are used in humid environments such as bathrooms with showers. Wood studs or carpet tack may also support mold growth. However, colonization of wood tends to take longer than the drywall paper and similar materials.

To prevent mold growth in high water use areas, products such as fiberglass coated drywall or cement board should be used. These materials do not contain cellulose and won’t support mold growth under most wetted conditions. If specially treated cellulose containing building materials are used, then the designers and contractors should carefully consider the manufacturer’s testing results and their applicability to the intended use before specifying or using these materials. Sometimes the fungal growth inhibitor chemicals can wash out of the treated cellulose, leaving these materials vulnerable to fungal growth when wetted again.

4. Roof Pollutant Sources Near Air Intakes

Typically, building vents such as those for the sewer system plumbing, bathroom, cooking, copier room, janitor’s closets, elevator shafts, emergency generator, boiler exhausts, and cooling tower are placed on the roof. Often the roof is surrounded by a parapet wall which can lead to the accumulation of pollutants on the roof top, especially when there is little or no wind. These pollutants can include hydrogen sulfide (sewer gas or rotten egg odor), carbon monoxide, nitrous oxides and particulates (combustion products), Legionella (aerosolized water sources), and chemical or other offensive odors (bathrooms and janitors closets).

By themselves, these building emissions may very well be appropriately placed on the roof. The problem arises when the outdoor air intakes for the building’s ventilation system are located in the same area. Many of the pollutants are heavier than air and can be entrained into the building’s air where they can cause annoyance, irritation, or actual health problems. Standard filtration methods, even when high Minimum Efficiency Reporting Value (MERV) rated filters are used, do not remove many of these pollutants.

5. Construction Dirt and Debris Left on New Building Ventilation Surfaces

If good housekeeping is not practiced during building construction, various potential pollutant sources can remain in hidden areas of the building including the ventilation system and inside walls. Air plenums can have accumulated dirt due to poor construction dust control, and trash including food and beverage items can be left behind to rot and create odors and other hazards such as attracting pests. This is particularly problematic if it occurs in the supply side of the ventilation system.

6. Ventilation Fan Cycling On and Off

This is a controversial “reason” and may apply differently in high-humidity vs. low-humidity environments.  When ventilation fans are cycled on and off, there is an assumption that energy is being saved. Though there may be some energy savings, there are negatives such as reduced air filtration (no air movement over filter = no air filtration) and stagnant or poorly mixed air, which can lead to more temperature differentials and “stale” air.  Also, regular starting and stopping could lead to increased wear on the fan components and less efficient operation, just as a car lasts longer and gets better mileage on the freeway as opposed to the city.

7. Using Hazardous Materials in New Buildings

Many people are under the false impression that asbestos is no longer used in building materials. It is still legal to manufacture and use many types of building materials containing asbestos in the U.S. Some examples include floor tiles, roofing mastics and felts, gaskets, pool plaster, and cement pipe (EPA).  Asbestos is still mined in places like Russia, China, and Brazil and is used throughout the world in building products. The U.S. imports approximately 1,000 tons of asbestos from Brazil for various uses each year.  Other hazardous materials in new products include lead (artificial turf, ceramic tile and fixtures, mini-blinds, solder) and orthorhombic cyclooctasulfur (associated with the generation of hydrogen sulfide gas in humid environments) in drywall typically manufactured in China (aka corrosive drywall).

Because the reuse of materials from demolished buildings is encouraged when building new green buildings, hazardous materials may remain in these reused materials. Examples include timber with arsenic containing wood preservatives used for new building framing, asbestos and lead in recycled concrete, polychlorinated biphenyls in window caulking and light ballasts, and mercury containing thermostats.

8. Building Envelope Issues that Can Lead to Fungal Growth

Water or moisture intrusions from outdoor sources such as high humidity, rain or snow, temperature extremes, and landscape watering that are associated with poor design, construction, or maintenance are all too common. Examples include thermal bridging allowing indoor condensation during cold weather, wall construction not allowing proper drainage or drying, improperly sloped landscaping, poorly sealed planter boxes against exterior walls, backward window well drainage, poorly sealed skylights, inadequately sloped or uneven flat roofs, missing roof flashing, etc.

9. Air Handling Units with Poor Access

If the air filters are difficult to change or access requires a contortionist, the chances diminish for getting filter changes at the proper intervals with correctly sized filters. When gaining access to the AHU cooling/heating coils, condensate pan, and fan to clean and maintain them becomes a day-long project requiring confined space procedures, cutting sheet metal, using scissor or cherry picker lifts, and/or various specialized tools, the likelihood of proper AHU maintenance deceases significantly. A lack of appropriate air filtration, dirty coils, condensate accumulation, and elevated moisture in the AHU can lead not only to poor IAQ but also to poor energy efficiency.

10. AHU Condensate Lines in Bad Locations or Improperly Installed

The condensate generated by fan-coil units during hot and humid days has to drain somewhere. Often times, it drains to a sewer drain where odors may be present. Since the condensate line is typically on the negative pressure side of the AHU and condensate is often not present, these odors may be entrained into the air ventilation system. If the p-trap typically installed to prevent this is not present (or is improperly installed or maintained), then the odors may be noted by building occupants.

In addition to the odor issue, an improperly draining condensate pan can overflow causing water damage and potential fungal growth on the building materials under it. The secondary pan designed to prevent this may either not function properly itself or may drain to a location where its function as a tell-tale is not effective (e.g., in a janitor’s closet slop sink or in another infrequently visited location). If this location allows the water to accumulate and wets building materials, then fungal growth may occur.

11. Inadequate and Improper Use of Products Identified as Low Emitting

One means of preventing or limiting new building related air contaminants is the proper specification and use of materials that off-gas or shed minimal or no amounts of chemical vapors or particles.  Most green rating systems, standards, and codes only address “volatile” compounds which do not include particulates; or more importantly, they may not address semi-volatile compounds which off-gas much more slowly and are not typically measured by currently used air testing methods or abated by flushing out the air of the building.

The “volatile” compounds that are addressed would typically be gone soon after their application and would not typically remain in significant amounts in the building after occupancy. However, semi-volatile compounds such as flame retardants, plasticizers in PVC, concrete, wallboard, etc., heavy petroleum hydrocarbons in coatings, pesticides, fragrances, etc., may remain long term and can have health effects at very low concentrations.

Note: “volatile” is in parentheses because this term is not well defined in the green industry.

Another issue can arise when a building material meets the specified low volatile organic compound (VOC) emission levels and is used in an inappropriate application. For example, roof mastic that meets allowable emission levels for its category is used as a floor moisture sealant under a bamboo floor creating elevated indoor VOC levels. In addition, the criteria for identifying acceptable concentrations of VOC emissions for coatings, adhesives, furnishings, flooring, etc. are typically based on IAQ exposure guidelines produced by the California Office of Environmental Health Hazard Assessment (OEHHA), which are not consensus based. The acceptable material or source emissions model assumes that the VOC (only) emissions in a small chamber will translate to occupant exposures in a building containing these materials or sources. The validity of this model is not well tested.

12. Inappropriate Air Quality Evaluation Parameters and Methods for New Green Building Pre-Occupancy

The current approach of many green building rating systems, standards, and codes for evaluating IAQ is either to not do it at all (e.g., flush out – refer to item 13) or to conduct a few snapshot tests using parameters of questionable value with poorly defined methods, especially for VOCs. It is hard enough just to get the experts in the field to agree on what materials are considered VOCs, let alone how they should be measured and what are acceptable levels. Clumping VOCs into a category known as Total VOCs (TVOCs) and assigning an acceptable TVOC quantity is like saying less than 500 total bacteria per cubic meter in the air is acceptable though, if 10% of those 500 were drug resistant mycobacterium tuberculosis, then 500 total bacteria is definitely not acceptable. On the other hand, if there were 1,000 total bacteria per cubic meter in the air and 90% were harmless skin cell related bacteria, then the 1,000 total bacteria per cubic meter would not represent an unacceptable condition.

VOCs are not the only problematic measurement parameters. Measuring total particulates (PM10) without knowing the types of particulates is just as problematic as the TVOCs. Measuring carbon monoxide in an unoccupied building with no combustion sources is a waste of resources and can give misleading results (e.g., false negatives).

Lastly, the methods specified (or not specified) in most of the green rating systems, codes, and standards are either too generic to give reproducible results or are methods not commonly used by field practitioners. For example, LEED has specified the EPA Compendium of Methods for Determination of Air Pollutants in Indoor Air. These methods are outdated and not used by most if not all IAQ professionals. Good luck finding a lab that uses these methods.

13. Depending Too Much on Building Flush-Out

Flush out of a building with outdoor air may have some value when VOCs or fine particulates have been released at the end of the construction process. However, most VOCs used during construction would have been long gone due to normal ventilation present during construction. Also, as described previously, semi-volatile compounds off-gas slowly and these compounds would only be slightly affected by flush out.  Building materials that shed particulates (e.g., fabric covered furnishings, carpet, ceiling tiles, etc.) would also not be significantly affected by flush out. Also, the outside air is not always “clean.”

14. Filters Not Performing Per Rating Due to AHU Design or Maintenance/Installation Issues

Though most green building rating systems, codes, and standards specify higher-than-normal efficiency for the filters to be used in a green building (e.g., MERV 13 or higher vs. MERV 8 or lower) there are no requirements that the AHU accommodate commonly available filter sizes and that gaps must be prevented and seals must be effective. If filters are not fitting or sealed properly, then the path of least resistance becomes the gaps between filters or the poorly sealed areas. The result is unfiltered air passing over coils where particles may accumulate and cause inefficiencies or microbial growth in humid environments. These unfiltered particulates would also enter the building’s airstream.

15. Installing Drywall before Roof or Windows are in Place

This one is pretty self explanatory. No matter how dry the climate, there is always a possibility for rain or snow. If interior drywall is installed before the building envelope is complete and the weather wets it, then fungal growth may occur and may not be removed due to it being hidden or covered up.

16. Not Designing or Constructing for Radon Mitigation

Radon is one of the most important indoor air pollutants with an estimated 20,000 lung cancer deaths attributed to it each year (EPA). It comes from the decomposition of uranium in the soil which is present in various concentrations throughout the U.S. and the world. Radon infiltrates the building through cracks and other penetrations in the foundation and, because it is very heavy, tends to accumulate in the lower parts of the building, especially basements.

Relatively simple mitigation actions can reduce the hazards of radon. These include providing an alternate path for the gas to go outdoors instead of indoors. Placing radon mitigation installations (e.g., sub-slab soil gas accumulation structures and venting through the slab) during construction is less costly and easier to conduct than doing it after the building is complete. By not installing radon mitigation during construction, the likelihood of radon being mitigated if it is found to be elevated in the building will be less likely, leading to the presence of a significant, preventable hazardous indoor air pollutant.

17. Exposed Fiberglass Insulation in Return Air Plenum above Ceiling Tiles

Airborne fiberglass can be very irritating to the respiratory system, eyes, and skin. Unfaced or exposed fiberglass insulation that is placed in the rafters or on top of suspended ceiling tiles can release fibers into the air where occupants can be exposed. This can happen either because the release area is a return air plenum or because maintenance staff “pops” a ceiling tile for access to mechanical equipment, wiring, plumbing, etc. to conduct maintenance activities.

18. Plumbing Construction Defects

During construction, issues may arise that affect plumbing, such as inadequately installed seals, poorly tightened fixtures, and nailing through water lines during drywall installation. These issues may not be immediately evident either during or shortly after construction. A slow leak can keep building materials wet for a long period of time and lead to fungal growth.

19. Ventilation Supply and Return Short Circuits

An easily correctable problem, especially in small office areas, is the placing of the room air return vent near or next to the supply vent. Instead of evenly circulating the air in the room, much of the air goes directly from the supply into the return, increasing the chance of temperature control and air distribution problems leading to poor IAQ.

20. Not Negatively Pressurizing Rooms with Pollutant Sources

 Rooms in a building where items are stored or used (or where activities are conducted) that may generate potential airborne pollutants should be placed under negative pressure to prevent those pollutants from entering other areas of the occupied space. Examples include break rooms or kitchens where cooking odors or combustion products are generated, janitor’s closets where cleaning chemicals or other hazardous materials are stored, copy and print rooms where gases such as ozone or ink particulates may be generated, and, of course, bathrooms.