Why Indoor Air Quality Matters More Than Ever
As we head into winter, many Australians spend more time indoors with windows closed, heaters running and ventilation reduced. Yet the quality of the air inside our homes is rarely part of mainstream conversations about housing.
In cities and towns across Australia’s southern states, many older homes can feel cold, draughty and damp during winter. Condensation on windows, musty smells, mould behind furniture and rooms that never quite feel comfortable are often treated as normal, but increasingly, research suggests our homes can play an important role in health and wellbeing.
According to CSIRO, indoor air quality has a direct impact on occupant health, wellbeing and comfort. Their research identifies ventilation, moisture, condensation, indoor pollutants, humidity and temperature stability as key factors influencing the health of indoor environments.
Poor indoor air quality is rarely caused by one issue alone. It can result from a combination of:
- inadequate ventilation
- excess indoor moisture
- mould growth
- unflued gas heating
- airborne particulates
- chemical off-gassing from materials and furnishings
- uncontrolled air leakage through the building envelope.
CSIRO also notes that indoor pollutant levels can often be significantly higher than outdoor concentrations, particularly in buildings with poor ventilation and moisture management.
The Hidden Impact of Dampness and Mould
Importantly, this is not simply a conversation about energy efficiency.
Increasingly, research is linking housing conditions to broader health outcomes.
A 2026 study published in the American Journal of Epidemiology by Maria Rosa Gatto, Rebecca Bentley, Ang Li and Erika Martino examined the impact of damp housing on people living with respiratory conditions such as asthma and other respiratory illnesses. The study found that damp housing conditions can contribute to increased emotional discomfort and reduced wellbeing for people already managing respiratory sensitivities.
The research reinforces that dampness and mould are not simply cosmetic or maintenance issues. They can affect comfort, wellbeing, and the lived experience of home, particularly for people already managing respiratory sensitivities.
Similarly, Rebecca Bentley and Kate Mason from The University of Melbourne have highlighted the strong links between housing quality, dampness, mould and respiratory health, arguing that healthier housing should increasingly be viewed as a public health issue rather than simply a construction issue.
Many existing homes were not designed with a modern understanding of moisture management, airtightness and indoor air quality in mind. During winter, this can create environments where condensation and poor ventilation become persistent problems.
Why Ventilation Matters
This is where building science and thoughtful design become important.
One of the biggest misconceptions is that healthier homes simply require “opening a window more often.” In reality, many older Australian homes rely on uncontrolled air leakage as a form of ventilation, allowing cold air, draughts, outdoor pollutants and moisture to move unpredictably through the building envelope.
At the same time, poor insulation and thermal bridging can create colder internal surfaces where condensation forms more easily. Over time, this combination of cold surfaces and excess moisture creates ideal conditions for mould growth.
Research from CSIRO led by principal research scientist Michael Ambrose found that improving a home’s airtightness can significantly improve comfort, energy efficiency and indoor air quality. The research showed that draughty homes can increase energy bills by up to 20 per cent, while poorly controlled air leakage contributes to cold indoor temperatures and discomfort during winter.
Importantly, the research also stresses that airtightness must be paired with proper ventilation and moisture management. As homes become more sealed, controlled fresh-air ventilation becomes essential to avoid condensation, mould and poor indoor air quality.
As Ambrose summarises:
“Seal tight, ventilate right.”
Recent Australian research has also highlighted growing concern around the relationship between air quality and long-term health outcomes, particularly as climate change and bushfire smoke events become more frequent.
What Passivhaus Can Teach Us
This idea sits at the centre of many building science-led design approaches, including Passivhaus.
Passivhaus is often discussed through the lens of energy efficiency, but many of its core principles also relate directly to indoor environmental quality and comfort. These include:
- continuous insulation
- reduction of thermal bridges (areas where heat escapes more easily through the building structure)
- airtight construction
- high-performance glazing
- balanced fresh-air ventilation
In some homes, filtered mechanical ventilation systems can also help reduce the entry of outdoor pollutants such as pollen, dust and bushfire smoke.
Research into Passivhaus-certified homes has suggested potential benefits for indoor air quality when airtightness is combined with properly designed ventilation systems.
A 2020 literature review by Alejandro Moreno-Rangel, Tim Sharpe, Gráinne McGill and Filbert Musau published in the International Journal of Environmental Research and Public Health reviewed 40 studies examining indoor air quality in Passivhaus dwellings, primarily across Europe. The review concluded that indoor air quality in Passivhaus-certified homes was generally better than in conventional housing, although occupant behaviour and outdoor pollution sources still played an important role.
The review also reinforces that airtightness alone is not enough. Adequate ventilation and moisture management remain critical to maintaining good indoor air quality and avoiding issues such as condensation, pollutants and mould growth.
Small Changes Can Make a Difference
Of course, not every home needs to become a certified Passivhaus to become healthier and more comfortable.
Often, meaningful improvements can begin with relatively practical measures such as:
- improving draught sealing
- upgrading insulation
- improving bathroom and kitchen extraction
- reducing condensation risk
- improving glazing performance
- addressing hidden moisture issues
- thinking more carefully about ventilation and material selection
The goal is not perfection.
It is creating homes that feel warmer, drier, healthier and more comfortable to live in, particularly during Melbourne winters when the impacts of poor housing performance become most noticeable.
As awareness grows around indoor air quality and respiratory wellbeing, housing is increasingly being recognised not just as shelter, but as an important part of long-term health, comfort and resilience.
