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Sick building syndrome (SBS) is a combination of ailments (a syndrome) associated with an individual's place of work (office building) or residence. A 1984 World Health Organization report into the syndrome suggested up to 30% of new and remodeled buildings worldwide may be linked to symptoms of SBS. Most of the sick building syndrome is related to poor indoor air quality.
Sick building causes are frequently pinned down to flaws in the heating, ventilation, and air conditioning (HVAC) systems. Other causes have been attributed to contaminants produced by outgassing of some types of building materials, volatile organic compounds (VOC), molds (see mold health issues), improper exhaust ventilation of ozone (byproduct of some office machinery), light industrial chemicals used within, or fresh-air intake location / lack of adequate air filtration (see Minimum Efficiency Reporting Value).
Symptoms are often dealt with after-the-fact by boosting the overall turn-over rate of fresh air exchange with the outside air, but the new green building design goal should be to avoid most of the SBS problem sources in the first place, minimize the ongoing use of VOC cleaning compounds, and eliminate conditions that encourage allergenic, potentially-deadly mold growth.
Building occupants complain of symptoms such as sensory irritation of the eyes, nose, throat; neurotoxic or general health problems; skin irritation; nonspecific hypersensitivity reactions; and odor and taste sensations.
Several sick occupants may report individual symptoms which do not appear to be connected. The key to discovery is the increased incidence of illnesses in general with onset or exacerbation within a fairly close time frame - usually within a period of weeks. In most cases, SBS symptoms will be relieved soon after the occupants leave the particular room or zone. However, there can be lingering effects of various neurotoxins, which may not clear up when the occupant leaves the building. Particularly in sensitive individuals there can be long-term health effects.
The contributing factors often relate to the design of the built environment, and may include combinations of some or all of the following:
Moisture buildup and mold growth Edit
Buildings often contain a large number of hidden internal cavities which are formed from skeletal construction methods. These cavities commonly exist inside walls and ceilings constructed using joists and trusses, and may also include attic, crawlspace, and drop-ceiling spaces. Such locations may have very low direct ventilation, but air does infiltrate in and out of these spaces as ambient atmospheric pressure changes occur.
Older building construction from before the development of insulation, moisture barriers, and composite materials tended to be drafty, cold, and wasteful of heating, but they also suffered few moisture problems. For example, before plywood was commonly used for floor construction, home floors were typically constructed with two layers of narrow boards laid at 90 degree angles from each other, and 45 degrees from the general lay of the floor joists. These boards had typically had rough gaps between them, which allowed air to seep freely in and out of wall and ceiling joist air spaces. Modern plywood floor construction is nearly impermeable by comparison, and allows no airflow into the joist spaces.
Moisture can be trapped and hidden within these cavities where it builds to 70% and 95% moisture saturation by weight. Moisture buildup can occur for example inside the wall cavities surrounding a high-humidity kitchen, bathroom, or bathing area that is poorly ventilated. There are few if any, mechanisms that operate to dry out these internal wall cavities once they become saturated with moisture. Ventilation of joist spaces is typically not considered important, though it could be accomplished during construction by drilling large vent holes inside each wall cavity, through the floor and ceiling plywood sheeting.
If such airflows are of hot, humid air, this moist, warm air may reach a dewpoint surface, especially if indoor temperatures are maintained much below about 78 degrees F. At this degree of moisture saturation, in this dark, undisturbed wall cavity space, most all molds, including stachy, thrive. Molds and bacteria rarely coexist. Molds produce generally toxic substances that create unwelcome, unhealthy environments for bacteria and insects, as well as human beings. The toxic substances generated by mold growth may become aerosolized, released and distributed to a much greater range by these unintentional airflows through the building's matrix until they may be inducted into the air conditioning and heating distribution systems and ultimately discharged into the breathing zone. These unintentional airflows create the toxicity and obscure the true source of toxicity and earthy odors as they distribute it.
Mechanical ventilation in a hot, humid climate may deliver water vapor into a building at the rate of approximately one pound of water per day for each cubic foot per minute per day of unconditioned outdoor ventilation air delivered.
Radon mitigation by mechanical ventilation in hot humid climates, (Florida) is known to create gradual increases in moisture saturation that suddenly lead to mold problems when moisture saturation of a favored mold food material reaches 70% by weight. This increasing moisture saturation process may take a few months or as long as four or more years.
The uninformed or poorly informed assume that the air conditioner will successfully remove such moisture, and it may if it is operating efficiently. Many air conditioners do not, and almost all of them decline in their ability to dehumidify efficiently over time. Residual moisture remains and soaks into materials as if they were sponges, on a march toward full saturation. In hot, humid climates, the worst months for mold are October, November, December and early spring...when air conditioners rarely operate and moisture saturation increases most rapidly.
Identification and termination of these unintentional building matrix airflows has rarely been recognized and acted upon, hence heroic efforts to heal the sick building have been largely unsuccessful. Out of a sense of frustration with enormously expensive and ineffective healing approaches, total building destruction is sometimes selected as a way out.
With proper application of currently available instrumentation, identification of unintentional building matrix airflows is relatively easy, quick and inexpensive for a knowledgeable, experienced, building science practitioner. Pressure and micropressure management can result in immediate odor and toxics distribution system termination. With application of correct technology, and often without installation of any additional equipment, relying only on what is already there, within hours of completion a sick building can begin a gradual drying out process to heal itself completely.
As Joe Lstiburek has said, the approach of building disassembly and rebuild or destruction on one hand (expensive) or micropressure management on the other (much less expensive) is decided by who is paying. Micropressure management correctly applied has the potential to eliminate the true cause of the sick building.
The other approach rarely addresses the cause and treats the symptoms only.
To the owner or operator of a "sick building", the symptoms may include high levels of employee sickness or absenteeism, lower productivity, low job satisfaction and high employee turnover. Clarification of the link between a sick building and employee health has and will likely continue to result in increased worker's compensation and personal injury claims. Business owners will likely find increasingly happy customers and a better bottom line with successful healing of sick buildings.
There might be a gender difference in reporting rates of sick building syndrome because women tend to report more symptoms than men. Along with this, there have been studies where they found that women have a more responsive immune system and are more prone to mucosal dryness and facial erythema. Also, women are alleged by some to be more exposed to indoor environmental factors because they have a tendency to have more clerical work where they are exposed to unique office equipment and materials (example: Blueprint machines), whereas men have jobs based outside of offices.
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