Australians spend approximately 90% of their time indoors. The materials that form the walls, floors, ceilings and finishes of those indoor spaces are not inert — they emit gases, absorb and release moisture, harbour or resist biological growth, and directly influence the air their occupants breathe.
The CSIRO has estimated that poor indoor air quality costs Australia $12 billion per year in health impacts and lost productivity. That figure was first published in 1998. Our buildings have not improved enough since then to meaningfully change it.
This is not a marginal concern. It is a central question for anyone choosing building materials – and one that most material marketing either ignores entirely or reduces to a single, meaningless label: “non-toxic.”
The evidence on how building materials affect occupant health is substantial, peer-reviewed and growing. What follows is an honest summary: which materials pose risks, which materials genuinely improve indoor environments, where the science is strong, and where the marketing has outrun the data.
What's in the air inside a building
Indoor air contains a complex mixture of chemical and biological contaminants. The three categories most directly influenced by building material choices are volatile organic compounds (VOCs), particulate matter, and moisture-related biological growth – principally mould.
Volatile organic compounds
VOCs are organic chemicals that evaporate at room temperature, releasing gases into the indoor environment. They are emitted by a wide range of building materials, finishes, adhesives, sealants and furnishings. According to the World Green Building Council, indoor VOC concentrations are commonly up to ten times higher than outdoor levels, and in some cases can reach one thousand times higher.
The health effects of VOC exposure range from acute symptoms – headaches, dizziness, nausea, and irritation of the eyes, nose and throat – to longer-term impacts including respiratory disease, liver and kidney damage, and suspected carcinogenicity for certain compounds. Formaldehyde, one of the most common indoor VOCs, is classified as a Group 1 carcinogen by the International Agency for Research on Cancer.
The primary building material sources of indoor VOCs include:
Pressed wood products – particleboard, MDF and plywood manufactured with urea-formaldehyde (UF) adhesives are the single largest source of formaldehyde emissions in most homes. These materials are found in cabinetry, shelving, flooring substrates and structural sheathing. Emissions are highest when the products are new and decrease over time, but formaldehyde off-gassing from UF-bonded products can continue for years.
Paints and coatings — conventional solvent-based paints contain significant VOC levels. Water-based paints have lower emissions but are not zero-emission. The “low-VOC” label is widely used but inconsistently regulated – in Australia, the relevant standard (AS/NZS 1580.104.1) sets maximum VOC content for different paint types, but compliance is self-declared by manufacturers. The difference between a paint marketed as “low-VOC” and one that genuinely has minimal emissions can be significant.
Flooring – vinyl (PVC) flooring emits phthalate plasticisers, which are endocrine disruptors, along with other VOCs from the PVC itself and from adhesives used in installation. Synthetic carpet emits a cocktail of VOCs from the fibre, backing, adhesive and treatments including 4-phenylcyclohexene (4-PCH), the compound responsible for new-carpet smell.
Insulation – spray polyurethane foam (SPF) insulation emits isocyanates during and shortly after application, which are respiratory sensitisers. Expanded polystyrene (EPS) and extruded polystyrene (XPS) emit styrene, a possible carcinogen. Fibreglass insulation itself has low VOC emissions but the formaldehyde-based binders used in some products can off-gas.
Sealants and adhesives – silicone, polyurethane and solvent-based adhesives used throughout construction emit a range of VOCs, often at high concentrations in the first days and weeks after application.
Moisture and mould
Material choices directly influence whether a building develops mould problems. Materials that trap moisture without allowing it to dry – non-breathable membranes, impermeable wall assemblies, synthetic insulation in poorly detailed cavities – create the conditions for mould growth. Materials that manage moisture dynamically – lime plasters, hempcrete, timber, clay renders, wool insulation – buffer humidity fluctuations and reduce the risk of condensation on cold surfaces.
This is not a marginal difference. Mould exposure is associated with respiratory infections, asthma exacerbation, allergic rhinitis and, in severe cases, hypersensitivity pneumonitis. The World Health Organization’s guidelines on indoor air quality identify dampness and mould as significant risk factors for respiratory disease. In the Australian context, where many older homes have poor vapour management and where climate zones range from tropical to alpine, material choices that actively manage moisture are a genuine health intervention.
Materials that harm: the conventional palette
Not every conventional building material is a health risk. Concrete, steel and standard masonry have low VOC emissions in their finished state (though concrete dust during construction is a significant respiratory hazard). Glass is effectively inert. The health concerns concentrate in a specific subset of materials – typically the finishes, adhesives and composite products that occupy the interior surfaces closest to occupants.
MDF and particleboard with urea-formaldehyde binders. The most significant single source of chronic formaldehyde exposure in most Australian homes. Found in kitchen cabinetry, bathroom vanities, built-in wardrobes and shelving. Alternatives include formaldehyde-free MDF (bonded with MDI or pMDI adhesives), solid timber, or plywood bonded with phenol-formaldehyde (PF) or soy-based adhesives, which emit formaldehyde at much lower rates.
Vinyl flooring. Phthalate plasticisers used to make PVC flexible are endocrine disruptors that leach into indoor air and dust over the product’s life. Children are particularly exposed because they spend more time on floors and have higher hand-to-mouth contact. Alternatives include linoleum (made from linseed oil, cork dust and jute – genuinely natural and low-emission), solid timber, cork, stone and ceramic tile.
Conventional carpet. Synthetic carpets and their underlay can emit over 40 different VOCs in the first weeks after installation. The industry’s own CRI Green Label Plus certification programme sets emission limits, but the threshold is a ceiling, not a guarantee of safety. Alternatives include wool carpet (naturally low-VOC, flame-resistant, moisture-buffering) or hard flooring with rugs that can be aired.
Spray foam insulation. MDI-based spray polyurethane foam emits isocyanates during application that are hazardous to installers and can affect occupants if areas are reoccupied too quickly. Once fully cured, emissions drop significantly – but the curing period and conditions matter, and improperly applied spray foam has caused documented indoor air quality problems. Alternatives include wool insulation, cellulose, wood fibre, hempcrete and cork insulation.
Materials that help: the natural palette
Natural building materials are not automatically healthy. “Natural” is a description of origin, not a guarantee of safety – asbestos is natural, and radon is natural. The audience research for this publication specifically flagged “chemical-free” as a term to avoid, because it is technically impossible. Every material has chemistry.
What the evidence does support is that several natural building materials actively improve indoor air quality through specific, measurable mechanisms – and that these mechanisms go beyond simply being “less bad” than conventional alternatives.
Hempcrete. Hemp-lime composite walls are hygroscopic – they absorb and release water vapour from the indoor environment, passively buffering humidity within the 40–60% relative humidity range that is optimal for respiratory health and minimises dust mite populations. Hempcrete walls contain no formaldehyde, emit no measurable VOCs in their cured state, and the lime binder creates an alkaline environment that resists mould growth. The indoor air quality in hempcrete buildings is consistently rated highly by occupants in post-occupancy studies, though the published data set remains small.
Timber. Solid timber emits terpenes – naturally occurring volatile organic compounds that give wood its characteristic smell. The evidence on terpenes is mixed: some studies associate low-level terpene exposure with reduced stress and improved mood (this is part of the scientific basis for forest bathing and wood-lined interiors), while other research indicates that terpenes can react with ozone to form secondary pollutants including formaldehyde. The honest position is that solid timber in a well-ventilated space is a low-risk, psychologically beneficial material – but the blanket statement that “wood is healthy” oversimplifies a more nuanced picture.
CLT (cross-laminated timber) introduces an additional consideration: the adhesives used to bond the layers. Polyurethane (PUR) adhesives are formaldehyde-free. Melamine-urea-formaldehyde (MUF) adhesives are not. For CLT buildings where panels are left exposed as interior surfaces, the adhesive specification directly affects indoor air quality.
Wool insulation. Sheep’s wool insulation is hygroscopic (it can absorb up to 35% of its own weight in moisture without losing thermal performance), naturally flame-retardant, and contains no formaldehyde binders. Wool fibres also have a demonstrated capacity to absorb and neutralise formaldehyde and other indoor air pollutants — a property that has been documented in peer-reviewed research and is now being actively developed as a functional air-purification mechanism by several manufacturers.
Cork. Cork is naturally antimicrobial, hypoallergenic, and resistant to mould, mildew and pests. It contains suberin, a waxy substance that makes cork virtually impermeable to water and gas, which means cork surfaces do not off-gas and do not harbour biological contaminants. Cork floors and wall panels provide thermal and acoustic insulation with effectively zero VOC emissions.
Lime plasters and renders. Lime is alkaline (pH 12–13), which means lime-plastered surfaces actively resist mould and bacterial growth. Lime plasters are also vapour-permeable – they allow moisture to pass through the wall assembly rather than trapping it at the surface. In older buildings and in retrofits, replacing cement renders with lime can significantly improve both moisture management and indoor air quality. Lime continues to absorb CO₂ from the air throughout its life through carbonation, contributing a minor air-purification function.
Clay and earth. Rammed earth, adobe and unfired clay products are inherently low-emission – they contain no synthetic binders, adhesives or treatments. Clay plasters are increasingly used as interior finishes specifically for their hygroscopic properties: they buffer indoor humidity more effectively than any painted surface, absorbing excess moisture in humid conditions and releasing it when the air is dry. This buffering capacity has a direct health benefit in reducing condensation and mould risk.
The biophilic dimension
Beyond chemical emissions and moisture management, there is a growing body of evidence on the psychological health impacts of natural materials in interior environments. This research falls under the broader heading of biophilic design – the principle that humans have an innate affinity for natural environments and natural materials.
The evidence is real but should be stated carefully. Systematic reviews of indoor exposure to natural elements – including wood surfaces, stone, natural light and plant life – have found associations with reduced stress (measured by cortisol levels and heart rate variability), improved mood, lower blood pressure and enhanced cognitive performance. A 2019 systematic review published in the International Journal of Environmental Research and Public Health confirmed these effects across multiple controlled studies.
The mechanism appears to be partly visual (the aesthetics of natural materials trigger a restorative response), partly tactile (the warmth and texture of wood, stone and natural fibres engage the somatosensory system differently from synthetic surfaces), and partly olfactory (the terpenes emitted by wood, for instance, are associated with the calming effects of forest environments).
The caveat is that most of this research measures short-term physiological responses in controlled settings. The long-term mental health impacts of living in a home built predominantly from natural materials, compared to a conventionally built home, have not yet been studied with the rigour that the claim deserves. The direction of the evidence is consistent and plausible – but it is not yet conclusive in the way that the VOC and air quality evidence is.
What to actually specify
For anyone making material decisions with health in mind – whether building new, renovating, or selecting finishes – the practical guidance is more specific than “choose natural materials.”
Ask for emissions data. Any product that will form an interior surface – paint, flooring, cabinetry, insulation – should be able to provide emissions testing results. In Australia, the relevant frameworks include Green Star indoor environment quality credits, GECA (Good Environmental Choice Australia) certification, and compliance with the formaldehyde emission standards in AS/NZS 2098.11 and AS/NZS 4266.16.
Prioritise vapour-permeable wall assemblies. In climates with humidity variation – which includes most of Australia – wall assemblies that manage moisture dynamically (lime, hempcrete, timber, clay) create healthier indoor environments than sealed, impermeable assemblies that rely entirely on mechanical ventilation to manage humidity.
Ventilate. No material choice substitutes for adequate ventilation. Even a building made entirely from natural materials needs fresh air exchange to manage CO₂, biological contaminants and moisture loads from cooking, bathing and breathing. Mechanical ventilation with heat recovery (MVHR) is the gold standard for controlled air exchange without energy penalty. In naturally ventilated buildings, cross-ventilation design and operable windows remain essential.
Read the fine print on “low-VOC” and “non-toxic” claims. These terms are marketing categories, not regulated standards. A “low-VOC” paint is lower than conventional paint, but the threshold varies by certification. “Non-toxic” has no legal definition in Australia. The question to ask is not “is this product low-VOC?” but “what are the specific emission levels, and what was the testing methodology?”
Consider the whole assembly, not just the finish. A solid timber floor finished with a high-VOC polyurethane coating is not a healthy choice. A formaldehyde-free MDF cabinet installed with solvent-based contact adhesive is not a healthy choice. The weakest link in the material chain determines the indoor air quality outcome.
1. Brown, S.K. (1998) Beating the $12 Billion Cost of Polluted Air | CSIRO, via BESS Sustainable Design Factsheets
2. Indoor Air Quality (2025) | Australian Centre for Disease Control
3. Air Quality in the Built Environment (2021) | World Green Building Council
4. Indoor Air Pollution and the Health of Vulnerable Groups: A Systematic Review Focused on Particulate Matter (PM), Volatile Organic Compounds (VOCs) and Their Effects on Children and People with Pre-Existing Lung Disease (2022) | International Journal of Environmental Research and Public Health
5. Physiological Benefits of Viewing Nature: A Systematic Review of Indoor Experiments (2019) | International Journal of Environmental Research and Public Health
6. The Effects of Interior Materials on the Restorativeness of Home Environments (2023) | International Journal of Environmental Research and Public Health
7. The Role of Green Building Materials in Reducing Environmental and Human Health Impacts (2020) | International Journal of Environmental Research and Public Health
8. Eco-friendly Construction Materials and Health Benefits in the Design of an All-inclusive Health Resorts (2023) | Frontiers in Built Environment
9. WHO Guidelines for Indoor Air Quality: Dampness and Mould (2009) | World Health Organization
10. IARC Monographs on the Identification of Carcinogenic Hazards to Humans — Formaldehyde, Group 1 | International Agency for Research on Cancer
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