Q&A with Tom Garrigan, Technical Director at BSRIA

With people in the UK spending around 90% of their time indoors, indoor environmental quality (IEQ) plays a crucial role in health, comfort, and productivity.

Throughout the 20th century, advances in building design and the widespread use of mechanical systems have helped to improve IEQ, often supported by readily available, inexpensive energy. However, many of these systems have not been optimised for efficiency, leading to unnecessary energy consumption.

As we shift towards a Net Zero future, the challenge is no longer just about enhancing indoor comfort, it’s also about adjusting to occupant needs, but doing so while significantly cutting carbon emissions. Behaviours have changed since covid, which has led to a shift in the design of our buildings, with a rise in spaces being reconfigured to support more flexible models.

However, a key question remains – how can buildings be designed and operated in a way that meets both occupant needs and stricter sustainability standards?

Net Zero has been discussed for years, but do you think there’s enough urgency as we approach 2050?

The 2050 Net Zero target has been in place since 2019, but the pace of change still needs to accelerate. While the construction industry is increasingly embracing energy-efficient materials, low-carbon design techniques, and smarter building management, there’s still a gap between ambition and widespread implementation.

It’s not just about cutting emissions – it’s about rethinking how buildings are designed, used, and adapted to maintain indoor comfort without compromising environmental goals. The urgency is growing, but stronger industry-wide coordination and policy support will be essential to drive meaningful progress and meet the demand for reducing emissions.

What are the key principles of indoor environmental quality (IEQ)?

IEQ is all about ensuring that indoor spaces support well-being, productivity, and overall comfort. The four core elements include:

• Thermal Comfort – Maintaining stable indoor temperatures through effective insulation, passive design strategies, and efficient heating and cooling systems.
• Air Quality – Ensuring adequate ventilation, low-VOC materials, and air filtration to reduce indoor pollutants and enhance occupant health.
• Daylight & Lighting – Maximising natural light access to reduce reliance on artificial lighting and improve well-being.
• Acoustics – Managing noise levels and sound absorption to create a more comfortable and productive indoor environment.

For these principles to be effective in a Net Zero context, they must be balanced with energy efficiency, using bioclimatic design strategies that leverage natural airflow, passive heating, and cooling to reduce reliance on mechanical systems.

How does IEQ influence Net Zero targets?

IEQ and Net Zero are deeply interconnected. A well-designed building reduces energy consumption and optimises indoor comfort using minimal resources.

For example, prioritising natural ventilation over mechanical air conditioning, using high-performance insulation, and incorporating smart shading and daylighting all contribute to reducing a building’s operational carbon footprint. By designing with both energy efficiency and occupant well-being in mind, houses can deliver high-quality indoor environments while meeting sustainability and ESG targets.

Instead of starting fresh, can retrofitting existing buildings help achieve decarbonisation targets?

Absolutely. Retrofitting is one of the most effective ways to decarbonise the built environment.

Rather than demolishing and starting from scratch, which comes with a huge embodied carbon cost, retrofitting allows buildings to be upgraded with energy-efficient systems, improved insulation, and enhanced ventilation. This extends their lifespan while reducing operational emissions, ensuring that existing structures meet modern environmental standards without the carbon footprint of new construction.

With careful planning, large-scale retrofitting could be a cornerstone strategy for achieving Net Zero, helping to bridge the gap between sustainable design and the reality of our ageing building stock.