Advice provided by: Sarah Gudeman, LEED AP, EIT, Morrissey Engineering, Inc.

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Timothy asks: Could you please give me an example of an indoor climate that you have experienced that you feel is unhealthy and explain the certain effects such an environment could have on the occupants; How could we improve such an environment?

Answer: Timothy, I’m not aware if I’ve experienced any of the following common indoor comfort scenarios first-hand (at least I can’t think of a specific example right now), which is actually a common scenario. Most building managers will tell you though, that most often occupant complaints stem from hot/cold calls. But unless the issue is something as obvious like falling asleep at your desk because you’re not getting enough ventilation air, having to wear your winter coat indoors, or sweating through your dress clothes, indoor occupant comfort issues aren’t sometimes easily identified.

As a result, the EPA conducted the Building Assessment Survey and Evaluation (BASE) study over a five-year period from 1994-1998. The purpose of the study was to characterize determinants of indoor air quality, or IAQ, and occupant perceptions in representative public and commercial office buildings across the U.S. This study provides normative IAQ data and baseline symptom rates in typical office buildings and establishes standardized testing protocols. The data collected as part of this study allow examination of relationships of symptoms and building characteristics; allow for the development of hypotheses to investigate sick building syndrome; and provide a stronger scientific basis for policy makers to develop guidance on building design, construction, operation and maintenance (http://www.epa.gov/iaq/base/study_overview.html).

I’d say that the most commonly addressed and controlled contributors to Indoor Environmental Quality (IEQ) by the mechanical engineer are thermal comfort, airborne contaminants, and odors. Providing conditions for human thermal comfort is a principal purpose of HVAC systems, but the concept of thermal comfort, “that condition of mind that expressed satisfaction with the thermal environment” (ASHRAE Standard 55) is definitely open for definition. Typically an acceptable range is if 80% or greater of building occupants are satisfied with the thermal environment, as determined most often by a thermal environmental survey. If less than 80% of building occupants are satisfied, then corrective actions should be taken to address each occupant’s specific concerns. Correcting these issues could require rebalancing of airflow to an area, adjusting setpoint temperatures, or adjusting air velocity (just to name a few).

While there are many airborne contaminants it’s important to be aware of, in non-industrial environments the most common airborne contaminants are Volatile Organic Compounds, or VOCs (sources include building materials, furnishings, cleaning products, etc), particulates (sources include cleaning, construction, paper dust, deteriorated insulation, combustion such as cooking, etc) and carbon dioxide (not dangerous as a toxic agent bust as a simple asphyxiant). These issues can be corrected by assessing the amount of exhaust and ventilation air delivered to specific spaces and using low-emitting materials where possible.

Finally, odors can include indoor and outdoor sources to various to mention. But again, occupant perception of odors can vary from person to person. It is the responsibility of the designer to address air intake locations and building exhaust discharge to minimize the possibility of odor infiltration. But in some cases, odors can be diluted by additional ventilation.