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Indoor Environmental Control Strategies

In contrast to traditional methods for ensuring good indoor air quality, which rely almost exclusively on ventilation strategies, source control strategies attempt to completely eliminate potential sources of contamination.

These strategies included carefully locating intake and exhaust air sites, limiting fibrous materials, and avoiding sites of microbial growth. By carefully selecting building materials, finishes, and adhesives, emissions of volatile organic compounds and other toxic and irritating substances were reduced.

Internal duct lining was prohibited as a preventative measure, to avoid possible contamination of the ductwork over time. Buildings built without internal duct lining require larger ducts and careful planning of mechanical room layouts so that sound can be attenuated.

Source isolation strategies were used to control contamination in the building that could not be completely eliminated. For example, desktop copiers were moved out of office areas into copy rooms. Laboratories and chemical storage areas, copy areas, food prep areas, loading docks, and toilet rooms each have dedicated outside exhaust; negative-pressure relationships are maintained to further discourage unwanted air flows.

Source dilution refers to ventilation and filtration of building air to dilute airborne contaminants. Filtration has been enhanced to 85 percent efficiency, and ventilation standards were developed so that the building could operate with ventilation rates 20 percent greater than those required by ASHRAE 62-89, to accommodate potential unforeseen circumstances.

Ductwork in the office areas was designed with flexible connectors for easy relocating, so adjustments can be made over time to improve ventilation effectiveness.

To predict the off-gassing of various materials during construction and occupancy, the team reviewed material safety data sheets and emission testing results. As a further precaution, the contractor was required to engage in emissions testing of the actual assemblies of materials, including adhesives and finishes, that were proposed for use in office areas.

Materials were tested using ASTM Standard D5116-90, "Standard Guide for Small-Scale Environmental Chamber Determinations of Organic Emissions from Indoor Materials/Products." Any material assemblies that contributed more than one-third of the allowable indoor air concentration for the specified contaminants would undergo further analysis prior to acceptance.

Setting Air Standards

A set of threshold values was established to determine the concentration of contaminants that would be permitted in the indoor air, based on what EPA experts determined to be both acceptable and achievable.

After construction was complete and prior to occupancy, baseline indoor air quality testing was required to verify that indoor air concentrations of contaminants fell below maximum allowable limits.

The table shows suggested maximum indoor air concentration standards to ensure good indoor air quality in regularly occupied buildings. The allowable air concentration levels had to be achieved prior to acceptance of building. The levels do not account for contributions from office furniture, occupants, and occupant activity.

Indoor Air Concentration Standards
Indoor Contaminants	Allowable Air Concentration Levels
Carbon monoxide (CO)	< 9 ppm
Carbon dioxide (CO2)	< 800 ppm
Airborne mold and mildew	Simultaneous indoor and outdoor readings
Formaldehyde	< 20 µg/m3 *
Total VOC	< 200 µg/m3 *
4 phenyl cyclohexene (4-PC)	< 3 µg/m3
Total particulates (PM)	< 20 µg/m3
Regulated pollutants	< NAAQS
Other pollutants	< 5% of TLV-TWA
*Above outside air concentrations. VOC: Volatile Organic Compounds 4-PC is an odorous contaminant constituent in carpets with styrene-butadiene-latex rubber (SBR). TLV-TWA: Threshold Limit Value - Time Weighted Average. Source: Facilities Operation Manual for EPA campus in Research Triangle Park, NC

IAQ Construction Procedures

To protect IAQ and lower overall construction costs, the team proposed an alternative to the extended post-construction flush-out period that was required by the State of Washington program. Instead, the specifications for the EPA campus include construction sequencing and continuous ventilation during construction, together with baseline indoor air quality testing.

Prior to construction, the contractor was required to submit a schedule describing the sequence of finish installation, to verify that wet materials, which can off-gas as they cure, would be installed before dry, fleecy materials, which can adsorb contaminants and rerelease them over time.

To provide further protection from contaminants, temporary ventilation with 100 percent outside air was required from the time the building is significantly enclosed until occupancy.

After construction was complete and prior to occupancy, baseline indoor air quality testing was required to verify that indoor air concentrations of contaminants fell below maximum allowable limits.

Based on predictive modeling using EXPOSURE, a program developed by EPA researcher Les Sparks, the team was able to demonstrate that use of low-solvent, low-emissions materials as specified, combined with ventilation during construction, would meet the prescribed thresholds.

As an enforcement measure, the contractor was required to ventilate the building until it met the established limits, and repeat the testing if the initial air quality testing results were not successful.

The Indoor Air Quality Facilities Operation Manual was both an end product and a method for tracking issues throughout the design process. Interim IAQ reports were produced at each major design milestone to document the design and to advance work on the manual itself.

The manual includes procedures for monitoring IAQ during occupancy, and it documents design decisions for building operators so that future building renovations will not inadvertently undermine air quality.

This project gave momentum to professionals defining improved standards for indoor air quality and environmentally preferable materials. The EPA has distributed the Indoor Air Quality Facilities Operation Manual to many interested professionals, as the procedures documented in it describe a proactive approach to protecting indoor air quality.

Sandra Mendler is a vice president and sustainable design principal in the San Francisco office of HOK. William Odell is a design principal with HOK's St. Louis office. HOK provided programming, site planning, architecture, interior design, lab design, and landscape design services for the EPA Environmental Research Center. This case study was adapted from an EPA publication entitled The Greening Curve: Lessons Learned in the Design of the New EPA Campus, which was produced with EPA funding under order number 7D-2124-NTLX.

This article is excerpted from The HOK Guidebook to Sustainable Design, copyright © 2000, available from John Wiley & Sons and at Amazon.com.

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The EPA Environmental Research Center designed by HOK. 1) laboratories; 2) offices; 3) atrium; 4) entry plaza with conference center below; 5) office tower with cafeteria below; 6) wetland pond; 7) pond; 8) wooded knoll. Photo: HOK Natural woodlands and wildflower plantings have been used in place of turf grass. A small wetland was enlarged and planted with native species. Photo: HOK Space planning designated almost 50 percent of the perimeter for open-office workstations, so light can penetrate into interior office areas. 1) laboratory; 2) laboratory office or support lab; 3) service corridor; 4) closed office; 5) open office area; 6) atrium. Image: HOK The atrium is covered with a combination of high-performance glass and translucent and opaque polymer panels to provide ample daylight without excessive heat loss or gain. Image: HOK Use of energy-efficient systems and passive solar architectural design strategies reduce the facility's energy use by 40 percent compared to U.S. Department of Energy statistics for comparable lab and office buildings. Image: HOK The contractor used a portable rock crusher to process excavated material, which was reused as structural fill and backfill. Three quarters of all construction waste was recycled. Photo: HOK The HOK Guidebook to Sustainable Design. Image: John Wiley & Sons   Click on thumbnail images to view full-size pictures.