SummaryThere is a movement in the commercial real estate industry topay more attention to the issue of indoor air quality (IAQ)throughout the design and construction stages of a building’slife. The “Green Design” movement also places emphasis onIAQ. This Design Brief defines indoor air quality, discussesventilation as a method of maintaining high IAQ, and introducesdemand controlled ventilation (DCV).With increasing concernsabout electricity demand in California, 2001 Title 24 Standardsrequire that DCV strategies be employed in high-density areas(occupant density of more than one person per 10 square feet).The brief ends with a discussion of seven ways to ensure that abuilding’s indoor air quality strategy is both energy-efficient andhealth-inducing.IntroductionThe advent of sealed buildings with precise environmentalcontrol has been one of the most profound technologicalchanges affecting the 20th-century world. For most of history,occupations kept people outdoors for long periods throughoutthe day. Today, the majority of the industrialized world’scommerce depends on information-based economies, whichrequires many people to spend the majority of their time indoors.Without a doubt, modern building ventilation systems played amajor role in fueling this powerful transformation; the quality ofworkplace ventilation cannot be underestimated in terms ofimpact on personal and national productivity.design briefenergydesignresourcesDesigning buildings for bothhigh indoor air quality andenergy efficiency requires anintegrated design approach.contentsIntroduction 1Ventilating Buildings 3Advanced Ventilation Technologies 12Design Issues for Healthy Buildings 17For More Information 23Notes 24INDOOR AIR QUALITYpage 2 indoor air qualityThere are many sources of indoor pollution.These sources rangefrom building materials and equipment to the human body.Pollutants created by the human body itself and its metabolicprocesses include carbon dioxide, heat, odors, and perspiration.With the industrial revolution came high-tech electronicequipment and various synthetic materials, both of which areadditional pollutant sources; the result is a myriad of pollutants intoday’s indoor environments.Defining Indoor Air QualityFor the past several years, there have been many debates amongindoor air quality specialists about the proper definition of indoorair quality and specifically what constitutes “acceptable” indoorair quality. Consequently, it is probably best to reference thecurrently accepted definition shown in the American Society ofHeating, Refrigerating and Air-Conditioning Engineers (ASHRAE)ventilation standard 62-1999 (Sidebar).1There are two key elements to this definition.The first is thatthe levels of contaminants at which health impacts can occurare not set by ASHRAE per se, but by “cognizant authorities.”This element recognizes that ASHRAE is a body of engineers,not medical specialists. The second element in this definitionis that ASHRAE has accepted that not everyone will find theindoor air quality acceptable, no matter what parameters arevaried.The figure of 80 percent acceptability is essentially anarbitrary one, but it has been used for decades. Bear in mindthat, in theory at least, in a building housing 1,000 people, 200people could find conditions in the building unsatisfactory, yetthe air may be considered “acceptable” via this definition.Therefore, the latest ASHRAE standard contains an importantcaveat, which reads as follows:Acceptable indoor air quality may not be achieved inall buildings meeting the requirements of this standardfor one or more of the following reasons:ASHRAE Definition ofAcceptable Air Quality“Air in which there are no knowncontaminants at harmful concentrationsas determined by cognizant authoritiesand with which a substantial majority(80 percent or more) of the peopleexposed do not express dissatisfaction.”1In a building housing 1,000 people, 200people could find conditions in thebuilding to be unsatisfactory, yet the airmay be considered “acceptable.”page 3indoor air quality(a) because of the diversity of sources and contaminantsin indoor air;(b) because of the many other factors that may affectoccupant perception and acceptance of indoor airquality, such as air temperature, humidity, noise,lighting, and psychological stress; and(c) because of the range of susceptibility in thepopulation.1Ventilating BuildingsDebate over solutions to indoor air quality problems hasincluded the merits of a broad “building systems” approachversus control of the many individual sources in the building.Abuilding systems approach includes proper application ofASHRAE 62-1999, which is key to providing good IAQ. However,a true building systems approach should go beyond ventilationalone to incorporate a holistic view of careful design, sourcemanagement, proper building commissioning, and a well-informed building operation and maintenance program.Most of the pollutants can, to some extent, be controlled byventilation, conspicuous exceptions being asbestos and sourcesof contaminants that originate within the ventilation systemitself (Figure 1). But the value of ventilation is that through astandard such as ASHRAE 62-1999, prescribed volumes ofdilution air can have a largely predictable effect on thereduction of many indoor contaminants. While there arenecessary caveats in the standard, such as the reminder that itcannot be expected to control all contaminants or potentialhealth effects, the standard plays a very valuable role in limitingdesigners’ liability. The practical effect is that products can bedelivered to the market that do an effective if not perfect job ofproviding acceptable working conditions for the majority ofbuilding occupants. This brief deals in part with sensing anddiluting certain biological contaminants, namely CO2and odor.However, as discussed later in this brief, the process of dilutingGases and VaporsVolatile and semivolatile organiccompounds (VOC): 300+ compounds,such as formaldehyde, benzene, andtolueneInorganic GasesCO2, CO, SO2, NOx, NH3, RadonFibersAsbestos, fibrous glass, man-madefibers, cotton, textilesDustsAllergens, house mites, pollens,feathers, danders, smoke (tobacco,wood, coal) MicrobesBacteria, protozoa, fungi, virusesFigure 1: Indoor air pollutantsof concernpage 4 indoor air qualitythese specific constituents does a credible task of reducing allindoor