Radiant Heating Design Guide
   


Indoor Air Quality at Home - Contaminant Sources
Source: Architectural Graphics Standards, The American Institute of Architects. Copyright (c) 2007 by John Wiley & Sons, Inc. or related companies. All Rights Reserved.
 


 

General Information About IAQ Design Integration

The interactions of elements that combine to provide good indoor air quality are now much better understood by experts; however, the design and construction community remain faced with competing design goals and unsubstantiated claims of material safety. Like all sustainable design strategies, IAQ requires design optimization based on individual project principles and goals. Following are selected attributes of good IAQ and how they relate to other sustainable design goals:

Energy considerations: Better air quality comes from more airflow, more air changes per hour, but more ventilation uses more fan and space-conditioning energy. Building type and occupancy, the existence of operable windows, and carbon dioxide sensors may all dictate how many air changes are appropriate for clean air.

Acoustical considerations: Hard, smooth materials requiring little maintenance are ideal from an IAQ perspective, but create more acoustical reflection.

Mechanical plant: The highest level of air filtration (e.g., HEPA filtration) significantly reduces air flow requiring greater fan energy and may or may not measurably improve comfort.

Commissioning and operations: Commissioning of mechanical systems involves additional time and cost but almost certainly improves air quality and optimizes performance. Commissioning of active IAQ systems such as dampers and sensors is essential. Protocols for more frequent maintenance need to be balanced against budgets and disruption to operations.

Material selection: Finish material selection weighs performance attributes such as maintenance and durability, and appearance attributes such as color and texture, against VOC emissions, life-cycle toxicity, potential for mold growth, and other health considerations.

Humidity: High interior humidity can be a side effect of natural ventilation or can come from humidification systems, interior uses such as cooking and bathing. Humidity control to inhibit mold growth and provide comfort is part of good programming and mechanical design.

Operable windows: These allow user control and flexibility, and can save or waste energy, depending on how a facility establishes operating protocols. Outdoor air is not always good air; it can include industrial pollution, dust, mold, and pollen that decrease air quality even as it provides ventilation and thermal comfort.

VOLATILE ORGANIC COMPOUNDS (VOCS) AND MATERIAL CERTIFICATION

Much attention has been given to VOCs as a source of indoor and outdoor air pollution and regulations have begun to address the issue. Certifications now exist that identify whether a material off gasses below a certain concentration of VOCs. Other considerations are more complex:

Not all VOCs are equal. The category volatile organic compound comprises a large group of materials; some are known carcinogens and others merely minor irritants. Toxicity at various concentrations varies. Most existing VOC criteria for architectural products treat all VOCs equally.

A material may have low concentrations of VOCs but may require maintenance or cleaning with materials that may themselves have high concentrations of VOCs.

Materials, finishes, and adhesives with low VOCs may not be as durable as other materials and may, therefore, create more of an air quality problem through necessary maintenance, replacement, or refinishing.

Materials are now certified to meet VOC restrictions. These include paints, adhesives, and floor tiles. LEED guidelines refer to other reference standards for total VOCs (TVOCs). The new gold level of Scientific Certification Systems' Indoor Advantage program sets thresholds for individual aldehydes and VOCs based on chronic reference exposure levels (CRELS) (e.g., benzene under 30 micrograms per cubic meter). Judgments are required by design teams to establish a consistent material selection policy.

CONTRIBUTOR: Mark Rylander, AIA, William McDonough + Partners, Charlottesville, Virginia.


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