The Environmentally Responsible Construction and Renovation Handbook
Chapter 3 - Indoor Air Quality and Materials Selection
The IAQ component of the Green Office Building Plan embodies the definition of acceptable indoor air quality from ASHRAE's draft revision to Standard 62. The goal is to design the office interior and ventilation system such that the occupants will be satisfied with the indoor air quality and such that there are not likely to be contaminants at concentrations leading to exposures that pose a significant health risk.
The provision of IAQ falls into two main categories;
- minimizing sources of pollutants within the office and
- providing adequate ventilation to ensure remaining pollutants are removed effectively.
Source control is always the first and most important step in mitigating contaminant levels and effects on office occupants. Ventilation strategies are then used to introduce fresh air into the space and carry out contaminants produced by both occupant activities and emissions from the materials within the building. Requirements for strategies to be used in construction, renovation, and commissioning are provided under a third section below.
The following list of requirements is a foundation for providing healthy, comfortable indoor air. For Renovation, Recapitalization and Fit-up projects, the Project Manager needs to discuss the viability of incorporating each of these measures into the design at an early stage in the Project Delivery System (PDS) as discussed in Part A of the GOBP.
3.1 Source Control
- Basement moisture control is required to be provided by moisture- and vapour-proof construction details on basement floors and walls and slab-on-grade floors. To prevent soil gases and moisture from entering the office building, details such as polyethylene sheeting under floor slabs and dimpled polyethylene or glass fibre or grooved polystyrene drainage layer on the walls shall be provided, where viable. Petroleum derivative water-proofing should not be used.
- Eliminate off-gassing from finishes that come in contact with indoor air. Water-based (latex) finishes and adhesives should be the products of choice. Where such categories exist, products that are certified by a recognized third party for their low concentrations of hazardous chemicals or that meet the certification criteria (NAFTA) should be chosen. The Environmental Choice Program (products bearing the EcoLogo label) is one such body. Ecologo products available include paints, caulking and adhesives.
- Specify materials with no/low formaldehyde, no/low VOCs, and/or other chemical emissions for 85% of the total interior surfaces in the building (i.e., all ceilings coatings, walls coverings and paints and floor coverings). Partitions and wall coverings made from vinyl or plastics contain a wide range of VOCs and should be replaced by products with less off-gassing potential. A wide variety of alternatives exist including textured wall coverings made from cellulose, natural fibre wall coverings such as sisal, decorative acoustical wall paneling made from fibreboard and cork, and so on.
- Carpeting has the potential to off-gas a variety of chemicals used in manufacturing. If carpeting is to be used it must be labeled by the Carpet and Rug Institute (CRI) certification program as a low VOC-emitting carpet. This program ensures that the emissions of the most common chemicals used in carpet manufacture meet the criteria for low emissions.
- Limit carpeting on floors: Ideally Carpeting shall cover no more than 50% of the floor area, but this will not always be practical.
- Adhesive for affixing carpeting is to be "low-tox" or water-based. Conventional glues are very high in VOCs and off-gas for long periods of time.
- Condensation on interior surfaces shall be prevented by ensuring all surfaces are at a minimum temperature of 10° C (50° F). Any individual heat-flow path through the structure should have an RSI value of not less than 0.5 (R-3) in locations with a winter design temperatures of -20° C (-4° F) or higher and not less that RSI 0.7 (R-4) for locations with lower design temperatures. Areas of thermal bridging that need to be considered include window frames, steel studs, flashings, fasteners or other highly conductive building components that penetrate from near the interior to near the exterior of the structure.
- Ensure fresh air is drawn from a clean location. Do not locate intake louvers near areas that could be contaminated by such pollutant sources as building exhausts, vehicular exhausts, cooling tower spray, combustion gases, sanitary vents, trash storage, and other hazardous air contaminants.
- Ozone-generating devices including those claiming to be air purification devices shall not be used.
3.2 Ventilation System Design
- Ensure ventilation air system design meets the requirements of ASHRAE 62. The standard provides details on calculating minimum fresh air requirements for offices and allowances for mixed air from adjoining spaces. Documentation provided with the drawings and specifications shall clearly show the design intent and calculations to verify compliance with the standard.
- Ventilation supply and exhaust grille performance design (i.e., direction and throw) and locations shall be such as to avoid short circuiting of supply air directly into the return grille.
- All outside air louvers and ducts (including economisers) shall be designed to limit intake air velocities to exclude rainwater entry. For most manufacturers the maximum allowable face velocity is approximately 2.54 m/s (500 ft/min).
- Air velocities through cooling coils and humidifiers shall be specified to prevent wetting of downstream surfaces. For most coils the maximum face velocity would be 2.54 m/s (500 ft/min) or less.
- No fibrous duct-liner or glass-fibre ducting shall be used. These materials hold moisture, are propagation sites for moulds, mildew, and bacteria and allow loose fibres to be blown into the space. Use non-porous (e.g., closed-cell polyethylene) duct-liners, exterior insulation, or acoustical baffles in strategic locations in lieu of linings. Use only metal or other hard surface ductwork.
- Ventilation exhaust air from kitchens, washrooms, smoking lounges, custodial closets, cleaning chemical storage areas, and dedicated printing/copying areas shall be vented directly to the outdoors with no recirculation through the HVAC system.
3.3 Indoor Air Quality During Construction and Commissioning
There are a number of construction practices which can be harmful to construction materials and adversely affect indoor air quality as a result. To guard against these practices the following measures should be taken at all renovation, recapitalization and fit-up sites:
- Protect construction materials (especially soft materials) from rain and other moisture sources.
- Ensure construction materials such as concrete are dry before they are covered with flooring or enclosed in wall cavities.
- Control fibre and particle release during installation of insulation and require thorough cleanup by this trade immediately after completion of this work.
- Verify all materials arriving on site comply with the environmental specifications and requirements under which they were purchased.
- Commission heating, ventilating, and air-conditioning systems to ensure that the design intention and specifications have been met, and proper amounts of fresh air are delivered to each zone.
Post testing can be used to determine that the indoor air quality is acceptable. Table 3.1 lists major pollutants generally found in offices along with guidelines for acceptable levels of those pollutants. The guidelines or standards are currently in force either in Canada, or in other jurisdictions where a Canadian recommendation does not exist.
3.4 Additional IAQ Improvement Opportunities
This section includes suggestions on additional measures which can be taken to improve indoor air quality above and beyond those considered essential to provide good IAQ.
3.4.1 Source Control
- Eliminate trim made from manufactured wood (MDF) containing formaldehyde and plastic trim containing VOCs. Finger jointed paintable trim should be used if it cannot be verified that other materials are free of emissions.
- Cabinets, desks and bookshelves are usually made from particleboard using urea-formaldehyde as a binder and employ adhesives containing VOC for adhering laminates. Alternative substrates such as Medite II which contain no formaldehyde can be used for cores. Paneling for cabinetry etc. can have all surfaces coated with a high quality sealer to keep formaldehyde from off-gassing. Reconditioned furniture can be specified and aging will have reduced the off-gassing potential to a significant extent.
3.4.2 Ventilation System Design
- Design for a minimum total air movement of 5.1 L/s/m² where conventional ceiling mounted diffusers and mixed air are used. Use diffused manufacturer's velocity and throw information to avoid stagnant air in occupied spaces. Other distribution systems such as displacement ventilation and systems that provide 100% ventilation air can provide good air distribution at significantly lower air movement
- Install displacement ventilation. Displacement ventilation has a floor to ceiling airflow pattern. Supply air enters floor level at low velocity carries pollutants up out of the breathing space and removes stale air from near the ceiling.
- Isolate potential pollution sources through separate zoning of areas where contaminants are generated (e.g., independently-ventilated, enclosed printing/copying area),
- Use high-efficiency filters (minimum 60% dust-spot efficiency) in all make-up and return air ducting. If outdoor air has high dust levels, use higher efficiency filters (80% dust spot efficiency) and include pre-filters (30% dust spot efficiency).
- Design air handler and control sequence to provide modulation up to 100% of air handler capacity in outdoor air as outdoor conditions warrant. This strategy is called an Economizer Cycle (see Section 5.6).
- Specify a night purge cycle to purge the building when there are minimal comfort concerns and minimal energy penalty.
- Evaluate natural ventilation through the use of operable windows. This can offer energy and functional advantages over mechanical ventilation. The potential for using natural ventilation in a building should be evaluated at the conceptual design phase. Considerations would also include pressurization and stack effects in buildings of six stories or higher. If appropriate the concept should be incorporated into the building design.
3.5 Case Studies of Office Building with High IAQ Standards
3.5.1 Steelcase Corporate Development Center
Description: The Steelcase Corporate Development Center (CDC) in Michigan was designed to encourage communication and creativity for 800 product-development professionals, and to help them create innovative office products, programs, and services in shorter time frames. The building, which was opened in 1989, is a seven-level pyramid-shaped building encompassing 55,740 m² (600,000 ft²), of which 58 percent is devoted to offices and public space, and 42 percent is used for laboratories and building support services. The purpose of the building, in addition to supporting team activities and fostering interaction, is to provide a productive environment in which 800 employees can work.
Features: The Steelcase CDC was designed to improve indoor air quality by controlling source emissions, proper ventilation, environmental control (temperature and humidity), and through proper maintenance. Source emissions of toxins were controlled by selecting non-toxic building materials, such as flooring, paints and finishes, and also by selecting office equipment that minimize toxin outputs when possible.
Ventilation contamination is controlled through 35 percent dust-stop efficiency pre-filters and 60 percent efficiency final filters. Large flow rates dilute any remaining contaminants thereby eliminating the use of expensive HEPA filters. The total air distribution was designed to be a minimum of 6.6 L/s per gross square metre of office (1.3cfm per gross square foot). The ventilation rate is up to 35 L/s per person of outdoor air (ASHRAE standard is 7.1 L/s). The 35 L/s represents an average air distribution for the entire building with the majority of air being distributed through the lab space with 100% outdoor air.
Both temperature and humidity are controlled for optimum comfort. The temperature is held constant at 23° C (77° C). The humidity is adjusted depending on the season to prevent accumulation of moisture that can be destructive to building materials, and can cause the formation of bacteria and mold.
A comprehensive computerized scheduling program of preventive maintenance for all building systems is used. Monthly inspections are made of key equipment; filters are checked monthly and replaced when required; and heating and cooling coils are cleaned annually. Proper housekeeping is essential in maintaining a dust and microorganisms free environment. Carpets are shampooed on a continuous basis with a complete cleaning cycle taking approximately two months. Carpet in high traffic areas is shampooed every other day and on an as-needed basis.
Results: The concentration of key toxins is significantly lower than prescribed by ASHRAE standard 62-89. Measured toxin concentrations with ASHRAE standard in brackets; carbon monoxide 0ppm (9ppm), carbon dioxide 531ppm (1000ppm), respirable suspended particulates 19 ug/m³ (50 ug/m³), and formaldehyde 0.021ppm (0.1ppm).
3.5.2 Ridgehaven Office Building
Description: The 73,000 ft² building originally built in 1981, which houses the City of San Diego Environmental Services Department (ESD), showcases effective energy efficient renovations at a reasonable cost. Healthy indoor air quality was a primary goal. The ESD wanted to avoid sick building syndrome and create a healthy building environment for all of its employees.
Features: Improved indoor air quality was achieved through careful material selection, a new mechanical system design, environmental construction methods, and a healthful building maintenance plan.
Environmental criteria for materials included selecting materials with minimal chemical emissions, and minimizing volatile organic compounds (VOC's) during installation. Additional considerations included building products that inhibit the growth of biological contaminants. Careful specification of low-VOC materials based on the environmental criteria included the Low-VOC Paints, Sealers, and Stains: met South Coast Air Quality Management District (SCAQMD) requirements for low-VOC coatings, and contained no formaldehyde, petroleum-based solvents or other toxins. Carpet tiles met State of Washington Indoor Air Quality Specification criteria for low-VOC product, backing had anti-microbial properties, and were installed with minimal use of low-VOC adhesive.
Linoleum sheet flooring consisted of natural material components with minimal VOC's and natural anti-microbial characteristics. Ceramic tile included glass and clay content, are inherently inert, and have no VOC emissions. Gypsum wallboard caused no VOC emissions. Steel framing is inherently inert with no VOC emissions
An entirely new mechanical system, ducting, and cooling tower were installed. The metal ducting was insulated on the exterior with a foil-faced batt to prevent man-made mineral fibers from becoming air-borne within the HVAC system. The new ventilation system was designed to the ASHRAE 62-89 standard.
Cleaning for occupant health and worker safety was the main priority for building maintenance. This included the use of non-toxic cleaning products that were water-based and contained minimal chemical emissions. In addition, a least-toxic pest control plan using no pesticides was also important in maintaining healthy indoor air quality.
Results: Approximately two weeks after occupancy, the building had no noticeable "new building" smell or odor that would typically be caused by chemical emissions from new materials and furnishings. Anecdotal evidence from chemically sensitive employees indicates a healthier indoor ecology for this green office building. The city experienced lower absenteeism and higher employee productivity in this healthy "green" building demonstration project.