Indoor air quality (IAQ)

Public awareness of IAQ is increasing, and extensive research continues to build the body of knowledge. With these trends, a better understanding of its effects has developed, and regulation regarding IAQ is becoming more specific. Smoking, for example, has been legislated out of all public buildings and there are standards regarding the prevention of Legionella. There is currently a translation of awareness and concern onto other aspects of IAQ such as formaldehyde emissions, volatile organic compounds, allergens and ventilation systems, to name a few. The NSW Legislative Assembly Standing Committee on Public Works outlined the following issues associated with poor IAQ:

• Increased risk of unacceptable public health
• Less satisfied occupants
• Reduced productivity
• Increased running and maintenance costs
• Reduced life of building components
• Possible litigation

Aiming for high indoor air quality through the design process, specification and construction assists in the prevention of many health issues, reduces designers’ and building owners’ levels of risk and, in doing so, produces more sustainable buildings that can contribute to improved wellbeing and productivity for the occupants.

The quality of air within a given space can be defined by a range of chemical, biological and physical characteristics. Indoor air is made up of gases and particles, many of which, at certain levels and in certain combinations become pollutants. These pollutants have an effect on human health, so their levels and combinations are said to affect the quality of the air. The quality of air can be determined by how well it:

• satisfies thermal and respiratory requirements;
• prevents unhealthy accumulation of pollutants; and,
• allows for a sense of wellbeing.

There are three types of pollutants:

1. Chemical 
   Formaldehyde, Volatile Organic Compounds (VOCs), pesticides, nitrogen dioxide, carbon monoxide, carbon dioxide, ozone and tobacco smoke
2. Biological 
   Viruses (air borne pathogens), bacteria, fungi including Legionella, mould, mildews, yeasts, dust mites and pollens
3. Physical 
   Asbestos fibres, radon gas, electromagnetic fields, dust, respirable suspended particulates and lead

The sources of indoor pollutants can be internal and/or external to the building and include:

• Building materials and furnishings (chemical, physical)
• Cleaning/maintenance agents (chemical)
• Office and HVAC equipment (biological, chemical, physical)
• Tobacco smoking, people and their personal care products (chemical)
• Car fumes, car parks (physical, chemical and biological)
• Outdoor air, industrial sources (physical – including bushfire smoke, chemical and biological)
• Pollens (biological)
• Electrical equipment (physical)
• Air temperatures, humidity levels (physical)

Chemical and physical pollutants tend to be most concentrated at their sources and dissipate over time and distance, but ventilation systems can cause recirculation and reconcentration of pollutants. Biological contaminants tend to be created in damp situations such as badly ventilated wet areas, failed waterproofing membranes or poorly detailed footings. As with other pollutants, these contaminants can be transferred by the ventilation system but, unlike their physical and chemical counterparts, biological contaminants can then multiply and reach critical levels within the mechanical ventilation systems away from the original source.

Back to top

Health of occupants

Sensitivity to indoor air pollutants varies greatly throughout the population, but significant health problems have been connected to indoor environment. Sensitive individuals may frequent any type of building. Hence it can be argued that all buildings should be designed so as not to harm those sensitive to the pollutants that are found within buildings.

Medical effects may be significant ranging from symptoms such as headaches to medical conditions such as asthma, allergy, lowered immunity, fertility problems, chronic fatigue and multiple chemical sensitivities. For some people, the combined effect of several minor pollutants can worsen a predisposed medical condition or trigger an attack. Prolonged exposure to indoor pollutants may be a risk factor in the development of allergies or even cancer.

Many modern building designs, their construction practices and materials increase the potential for low quality indoor air. Most commonly, buildings are closed, insulated and conditioned with relatively low fresh air intake levels and incorporate materials that use complex glues and laminates and release chemical pollutants into the air. Pollutants and associated issues can all be reduced through well-recognised design and specification methods.

Providing thermal comfort through the appropriate use of shading, insulation, thermal mass and natural ventilation, helps to achieve comfortable internal temperatures for a higher proportion of the time without having to resort to artificial heating and cooling systems. It is desirable to have a combination of passive and active thermal control systems. The key is to get the best out of both in order to maximise IAQ.

Delivery of indoor air with appropriate levels of humidity so as to prevent the growth of mould is of particular importance in cooler, moist climates. This involves consideration of construction type, so as to control moisture penetration, and consideration of fresh air delivery through passive and/or active means. Refer to the Australian Building Codes Board Condensation in Buildings Handbook. 

Back to top

Relevance to architects 

Architects and other building consultants owe a duty of care to their clients to design buildings that do not negatively impact upon the health of the occupants. Related to this, the Institute's Code of Professional Conduct obligates architects to design buildings that do not adversely impact the environment. Comprehensive environmental design principles incorporate building health considerations.

In recent years building health has been a topic on government agendas locally and internationally, as the adverse implications for occupants’ health raises the potential for legal action against parties responsible for built environments. The architect must be aware of the duty of care that they have to all potential users of their buildings, not just to the client for whom they are designing. As noted above, a building health problem may be created by multiple factors. In addition, the complexity of modern building systems means that responsibility can include a range of consultants on any given job. Hence, there may be shared liability between various consultants and the architect. If a building is not maintained correctly or with due care, owners and managers can also be held liable.

Architects and other building professionals cannot claim ignorance of building health issues, given the amount of information publicly available. Increasing knowledge and awareness has led to regulatory bodies bringing about guidelines and standards that relate to particular aspects of building health. Awareness has also led to increased scrutiny and raised expectations of building performance levels.

Primary prevention of building health problems through design and building maintenance, rather than treatment of symptoms, is the most effective method of mitigation from both a cost and a health point of view. Due to the risks that many buildings can pose to health, architects are in a position to assist the move to primary prevention of illnesses through the design of healthy buildings. This preventative action has the potential to significantly reduce the associated medical spending in Australia.

Back to top

Building life-cycle processes

To achieve high IAQ, strategies must be undertaken at all stages of design, construction and operation of a building. Following is a brief list of considerations according to the various stages of the building’s life cycle with particular relevance to commercial, institutional and public buildings.

Brief development

• Definition of goals regarding IAQ, in conjunction with client
• Education of client and other stakeholders in IAQ issues

Design

• Passive design and HVAC design as discussed above

Specification

• Materials and system specification for high IAQ as discussed above

Handover/commissioning

• Operations manual
• HVAC commissioning
• Flushing of completed and renovated buildings

Building Operation and maintenance

• Monitoring of pollutant levels – potentially through a Building Management System
• Surveying of occupant satisfaction with IAQ levels
• Purchasing policies for furnishings, office equipment and cleaning products
• Maintenance regime – ensuring correct maintenance of HVAC systems, as well as cleaning of furnishings and surfaces within the building

Remember that for IAQ, the whole is greater than the sum of the parts. Failing to undertake any one of the above strategies may become the cause of poor IAQ even if all of the other strategies have been followed. In addition, multiple negative IAQ factors can produce problems greater than the sum of parts for certain sensitive sectors of the population.

Back to top

HVAC design

Heating, Ventilating and Air-conditioning (HVAC) design, incorporating a high percentage of fresh air intake, usually ensures higher IAQ. Unfortunately, HVAC design for high IAQ often competes with other environmental considerations. For example, in colder climates there is a tendency to try to reduce fresh air intake as a means of reducing energy consumption. The higher the proportion of fresh and cold air that is being introduced into a building, the higher the amount of energy required to heat that air to a comfortable temperature. The same is true in reverse for hot climates.

The following are key factors in HVAC design:

• Incorporating a high level of fresh air intake and, therefore, a low level of air recirculation.
• A comprehensive maintenance regime for the HVAC system.
• Air intake position. Carefully placed intakes will limit the external pollutants being drawn into the building and ensure that expelled air (from the building or adjacent buildings) is not re-circulated.
• Delivery control by individual occupants.
• Ventilation of specific components within a building, eg stoves in kitchens, copy areas in offices and toilets.
• Achieving humidity levels to prevent mould/bacterial growth.

Back to top

Material selection

Building materials and components commonly contribute indoor pollutants. Avoiding materials that produce emissions is the first step. Types of materials that are the most commonly associated with the emission of indoor air pollutants are:

• Paints and stains that emit VOCs and other chemicals. Low emission products are now readily available.
• Plastics and vinyls that emit VOCs and other chemicals. These can be either avoided or replaced with a lower emitting product.
• Composite timber products require close consideration. One major factor is the use of formaldehyde-based glues in these products. Particleboard, MDF and plywood products can emit formaldehyde during installation and over a period of years in situ. Recent advances in adhesive types has lead to very low levels of emissions being achievable, however these products must be carefully specified so as not to allow substitution of inferior products. An emission rating system is in place for composite timber products. E0 represents the lowest level of emission, increasing to E1 and E2.
• Adhesives are used extensively and are often the cause of emissions of formaldehyde and other chemicals. Design to minimise the need for adhesives by specifying other methods of fixing or seek out alternatives to glued products.
• Sealants such as epoxies and other petrochemical-based sealant products can have high pollutant emission levels. Try to avoid the need for these products.
• Carpets can be both a source and a sink for air pollutants.

For most products, emission levels are highest immediately after application, but emissions can persist at low levels over long periods of time. If products known to be the cause of pollutant emissions must be used, it is important to flush a building for as long as possible after installation of the products, before occupants move into the building. Emission levels tend to increase at higher temperatures, so it is possible to conduct a ‘bake out’ in which the HVAC system is set to a high temperature for an extended period of time before occupation in order to speed up the emission of pollutants from materials.

It is also important to consider maintenance issues of materials by selecting materials and finishes that are easy to clean without the need for harsh chemicals. Chemicals used during the operation of a building have the potential to produce much greater levels of indoor air pollutants over the life of a building than the materials of which the building was initially constructed.

Because fitout replacement occurs at a greater frequency than the replacement of other components in a building, fitout materials are most likely to be the newest and therefore highest-emitting products within the building. In addition it is the fitout materials with which occupants are in most frequent contact. Special consideration should be given to the selection of fitout materials so as to reduce emissions.

Electrical component design should consider the potential impact of Electromagnetic Radiation (EMR). EMR is generated from any electrical systems within the building. If possible, isolate electrical mains switchboards and systems controls from occupied areas of buildings. Wiring routes can be designed to maximise the distance between the circuits and occupants, particularly where higher voltages are concerned.

Back to top

Legionnaires' disease

Legionnaires’ disease is a respiratory disease that may be transmitted by the inhalation of aerosol-borne micro-organisms from infected waters and soils. As the source of infection may be the air-conditioning or warm water systems of the building, measures to keep the risk to a minimum should be taken at the design stage. Legislation varies from state to state. In some jurisdictions it is necessary for cooling water systems to be registered with the state or local authority.

Consideration should be given to eliminating water cooled systems in new installations. Where this is not practical, measures should be taken to protect against the spread of Legionnaires’ disease, and this should be made clear in the brief to consultants. Give careful consideration to the location of cooling towers, the location of air intakes, prevailing winds etc.

Careful consideration must also be given to the design and installation of warm water systems, showers, water features, irrigation systems, and other fixtures or fittings that are associated with water. Existing water cooling and warm water installations require correct maintenance procedures, involving specialist advice on contamination control. In many cases, regular testing will also be required.

Standards Australia publishes a Standard in three parts that covers design, installation and maintenance of air-handling and water systems to control micro-organisms in buildings. AS/NZS 3666 Air-handling and water systems of buildings - Microbial control is called up by legislation in some states, and should be considered in the building design process.

Because the regulations pertaining to the control of Legionnaires’ disease in buildings change frequently, architects should take steps to ensure they keep up to date.

Back to top

References and further reading

ASHRAE Standard 62.2-2013, Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings

Brown, Stephen. ‘Indoor Air Quality Australia: State of the Environment Technical Paper Series (Atmosphere )’ Department of the Environment, Sports and Territories; Canberra 1997

Brown, Stephen. ‘Case Studies of Poor Indoor Air Quality in Australian Buildings’, 14 International Conference on Clean Air & Environment, Oct 18-22, Melbourne, CASANZ

CSIRO BCE Technical Report TR97/3 December 1997, Indoor Air Quality Guidelines for Sydney Olympic Facilities

Department of Agriculture, Water and the Environment ‘Indoor Air’, accessed 19.05.20, http://www.environment.gov.au/protection/air-quality/indoor-air

Global GreenTag: web-based materials database for sustainable materials and products

Robertson, Heather, Achieving good indoor air quality in new buildings, Australian Institute of Building Papers NO 4 1990/1

Shaw, C, Salares, V, Magee, R, Kanabus-Kaminska, M, 1999, Improvement of Indoor Air Quality in 4 Problem Homes, Building and Environment no 34, 57-69

World Health Organisation, 2009, WHO Guidelines for Indoor Air Quality: Dampness and Mould, WHO Europe, Copenhagen

Australian Standards:

AS/NZS 1668.2 The use of mechanical ventilation and air-conditioning in buildings – Mechanical ventilation for acceptable indoor air quality

AS/NZS 3666 Air Handling and water systems of buildings (relating to prevention of Legionella and other water and airborne bacteria)