Healthy buildings have a direct, daily impact on how people feel and perform. From apartments and offices to schools and hospitals, well-designed spaces support physical health, boost mental wellbeing and protect building value over time.
That’s why healthy indoor air quality (IAQ) has become a compliance expectation and a real selling point for design-led projects.
Two of the biggest drivers of a healthy building are indoor air quality and natural light. Yet all too often, air quality is misunderstood or overlooked in early planning, leading to uncomfortable spaces, increased energy use and expensive fixes down the track.
In this article, we answer common questions about designing for optimal indoor air quality and show how early, performance-based planning can create healthier, more resilient buildings.
What is indoor air quality, and why does it matter?
Indoor air quality (IAQ) refers to the condition of the air inside a building and its direct impact on the health, comfort and overall wellbeing of occupants.
In simple terms, indoor air quality is a measure of how clean and healthy the air is inside a building. Poor IAQ affects comfort, focus and health: headaches, fatigue and difficulty concentrating are common. For people with asthma, allergies or other respiratory issues, symptoms can worsen. In schools and workplaces, bad air quality often means more sick days and lower productivity.
Common indoor air pollutants include:
- carbon dioxide (CO₂) from people breathing in busy spaces
- volatile organic compounds (VOCs) from paints and finishes
- mould spores and moisture from humidity or water leaks
- airborne germs, which build up in stuffy, poorly ventilated rooms.
If you’ve ever felt drowsy in a stuffy meeting room or noticed a lingering musty smell in a classroom, you’ve experienced the impact of poor air quality firsthand.
How to improve indoor air quality in a new building
Improving indoor air quality begins with thoughtful planning and design, going beyond simply meeting mechanical ventilation requirements. By considering IAQ early in the design phase, you can significantly enhance occupant comfort and health while boosting building performance.
Here’s how to improve air quality from the beginning:
- Design for fresh air: Maximise opportunities for natural cross-ventilation with well-placed, operable windows. Where this isn’t possible, use mechanical ventilation that brings in outside air.
- Choose healthy materials: Use paints, sealants and flooring with low (or no) VOCs to avoid introducing new pollutants into indoor air.
- Get the details right: Design ventilation systems to avoid stagnant corners and ensure even air distribution. Consider the use and occupancy of each space—windowless rooms or basements need special care.
- Plan for maintenance: Design systems to be easy to clean and service. Poorly maintained filters and ductwork can quickly undermine final performance.
Case study: Fixing air quality in windowless basement rooms
As the density of multi-residential projects increases, developers are making greater use of below-ground levels for habitable spaces. These might include media rooms, home gyms, recreational areas or additional bedrooms. While this is allowed under building codes, these spaces present a significant risk in terms of indoor air quality and condensation management.
Basement rooms pose clear air quality risks. In one recent Class 1a residential dwelling, we were engaged to assess the airflow and ventilation strategy for a group of units that included basement-level living areas. The original design relied on internal air recirculation and did not include mechanical ventilation directly connected to the outside. As a result, several issues arose:
- The absence of windows and vents limited natural airflow entirely.
- Humidity increased due to human activity, including breathing, exercise and shower use.
- Warm air exhaled by occupants condensed against cool basement walls, creating moisture accumulation.
- Stagnant air and moisture encouraged mould growth, particularly within wall cavities and behind plasterboard.
Most worrying was the appearance of black mould, a fungal species known to release mycotoxins that can trigger respiratory issues, allergic reactions and long-term health complications. For the building owner, this created a dual risk: potential health complaints from occupants, and structural concerns from mould getting into framing and finishes.
We recommended mechanical ventilation. Fresh air was drawn in from outside while moist, stale air was expelled. This straightforward fix reduced humidity, stopped the mould from returning and brought the building up to code.
How does air quality relate to compliance?
Australia’s National Construction Code (NCC) and AS 1668.2 require effective mechanical ventilation in habitable rooms that don’t have windows (except for kitchens, bathrooms and laundries). Recirculating the same indoor air isn’t enough; pollutants must be removed, not just spread around. Mechanical ventilation systems must:
- deliver enough airflow to keep rooms fresh and safe
- maintain humidity and CO₂ at healthy levels
- work reliably, in both high-use and low-use spaces.
Where windows can’t be installed due to planning or structural constraints, we typically recommend mechanical ventilation systems with dedicated supply and exhaust paths, directed to external air sources. Best practice is to aim for at least six air changes per hour, particularly in enclosed rooms.
How DDEG ensures better indoor air quality
Natural ventilation is always best, but it’s not always possible. For rooms buried deep in the floor plan, we work with architects and builders to implement alternative, performance-based solutions. We:
- design mechanical ventilation tailored to each room’s layout and use that meet or exceed NCC requirements
- undertake performance-based design assessments for rooms without access to natural ventilation
- test and verify air movement and humidity on site
- provide clear compliance pathways so projects meet health standards and avoid avoidable rework
- conduct system integration reviews to ensure energy efficiency and maintainability in enclosed spaces.
Even in challenging designs, we can help ensure buildings are safe, comfortable and compliant.
How to prioritise wellness from the start
Healthy indoor environments require intentional design. By prioritising indoor air quality from the very first design sketch, you help future-proof your project, improve comfort and safeguard long-term value.
Questions to ask at the design stage:
- Are ventilation strategies good enough for every space, including basements and interior rooms?
- Will each area feel fresh, comfortable and productive year-round?
- Is expert support needed to achieve the best outcome?
Get expert advice on indoor air quality
The earlier you think about IAQ, the better the outcome. DDEG’s team helps you get air quality right from the start, designing healthy, energy-smart spaces people want to be in, without compliance (or actual) headaches.
Ready to breathe easier on your next project? Get in touch to discuss practical, performance-driven air quality solutions.