Ventilation, Performance, and the Road to Better Indoor Air Quality

In our latest episode of Air Quality Matters, I sat down with Tom Hetherington Heywood , the MVHR Department Manager at 21 Degrees , to discuss the intricacies of ventilation systems, the philosophy that drives their team, and why we need to shift our thinking toward performance-focused design. If you’ve ever wondered about the future of ventilation systems, what makes them truly effective, and how they can improve air quality in homes and buildings, you’re in the right place.

The Importance of Performance in Ventilation

Tom and I both agree performance should be at the forefront of any conversation about ventilation systems. Often, designs are focused on product specs rather than performance outcomes. But is it enough to just install a unit, or should we focus on the performance we expect from that unit in real-world conditions?

Tom highlights that one of the first questions they ask clients is why they want a mechanical ventilation system with heat recovery (MVHR). Is it required for planning purposes, or are they targeting high-performance standards like Passive House? Understanding the need behind the installation shapes the design and the outcome.

"Switching over from a product spec to a performance specification is key, but so is educating the industry to understand the product from a performance perspective," says Tom.

This means ensuring that every system installed not only meets the building code but delivers the outcomes necessary for improved air quality, occupant comfort, and energy efficiency.

The Trade-offs of High-Performance Ventilation

One of the key takeaways from our discussion was the balancing act between heat recovery efficiency and energy consumption. Tom explains that while it’s tempting to chase the highest levels of heat recovery, this can sometimes lead to increased energy use from the system's fans.

For example, a unit with a 92% heat recovery efficiency may sound appealing, but it might not always be necessary. Depending on how well the building fabric is designed, a slightly less efficient unit might perform just as well without wasting energy. This leads to the question: do you need the best, most expensive unit, or can a more cost-effective solution work just as well?

For listeners in the commercial sector, there’s often a trade-off between achieving high heat recovery and managing the energy consumption of the system’s fans. It’s important to find a balance that fits the building's needs while optimising both energy efficiency and comfort.

The Role of Air Quality in Ventilation Design

We also touched on an often-overlooked aspect of ventilation systems: their role in improving indoor air quality (IAQ). While the primary focus of many installations might be heat recovery, the fact that these systems bring in fresh, filtered air and expel moisture is a significant benefit.

Tom emphasises that improving IAQ isn't just about creating a solution for airtight buildings. It’s also about enhancing the health and well-being of the occupants. With good ventilation, we reduce indoor pollutants, moisture, and even potentially harmful chemicals from entering the home. The payback from an MVHR system isn't just in energy savings; it's in the long-term health benefits for both the building and its occupants.

Overcoming Installation Challenges

The challenge of installing MVHR systems in retrofitted homes is something Tom sees often at 21 Degrees. While it's easier to integrate these systems into new builds, retrofitting existing homes requires innovation and careful planning. The team at 21 Degrees works closely with architects and contractors to ensure the design fits within the building’s structure while maintaining optimal performance.

One surprising insight from Tom is that some of the best MVHR installations have been completed by self-builders. Their lack of previous experience means they’re more likely to follow detailed designs closely, ensuring the system works as intended.

Tom’s team ensures that every system is commissioned—this means checking airflow rates, sound levels, and overall performance to ensure the system is working as designed. For them, commissioning is as critical as the design itself because it verifies that the intended performance is being achieved.

Looking Ahead: A Shift in Industry Standards

One of the biggest challenges facing the ventilation industry is the gap between installation and expected performance. There’s a common assumption that once a system is installed, it will simply work. However, without proper design and commissioning, many systems underperform—whether it’s due to poor airflow, noise issues, or even a failure to provide adequate ventilation.

As the industry moves forward, Tom believes that a more rigorous approach to design and performance specification is essential. He advocates for a shift in building standards that would require independent commissioning of ventilation systems, a practice already seen in some parts of Europe. This would ensure that every installed system is working as intended and delivering the performance needed to improve both energy efficiency and air quality.

In this episode, Tom Haywood provided a clear roadmap for what we need to do as an industry to improve ventilation outcomes. It's not just about installing systems—it's about ensuring they perform, improve air quality, and offer long-term benefits for both the building and its occupants. By focusing on performance-based design and rigorous commissioning, we can begin to close the gap between expectations and real-world outcomes.

For anyone involved in building design, retrofitting, or even considering an MVHR system for their home, it’s essential to think beyond the product and focus on the overall performance. As Tom pointed out, ventilation isn’t just a box to tick for compliance—it’s an investment in the health and sustainability of our built environment.

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