Passive Ventilation Systems for the UK Built Environment

Passive ventilation systems offer a resilient alternative to fully mechanical solutions by exploiting natural driving forces, including wind pressure and buoyancy, to deliver airflow without continuous energy input.

Key benefits include:

• Reduced operational energy demand

• Improved indoor air quality through continuous background ventilation

• Lower system complexity and maintenance burden

• Compatibility with overheating mitigation strategies under Approved Document Part O.

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The introduction of Awaab’s Law is a welcome and necessary step, bringing renewed attention to the health risks associated with poor indoor air quality. With people in the UK spending over 80% of their time indoors, ensuring safe and healthy internal environments is fundamental to public health, housing quality, and wider economic outcomes.

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Damp and mould remain widespread, particularly in social housing, and are often incorrectly attributed solely to poor insulation. In practice, even well-insulated homes are vulnerable when ventilation is inadequate. Insufficient air exchange allows moisture and pollutants—such as carbon dioxide and particulates—to accumulate, creating conditions conducive to mould growth. This is why Approved Document Part F mandates minimum ventilation rates to safeguard occupant health.

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However, rising energy costs have altered occupant behaviour. Evidence submitted to the Renters’ Rights Public Bill Committee (RRB85) highlights that tenants frequently close windows and block trickle vents to avoid draughts and heat loss. This creates a systemic challenge: residents limit ventilation to manage heating bills, while landlords are left unable to prevent damp and mould without adequate air circulation.

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Addressing this challenge requires ventilation strategies that do not impose a perceived or actual energy penalty on occupants. Low-energy and passive approaches, particularly those suited to retrofit, offer a practical way to protect health while maintaining affordability. PassiHEAT has been developed with this balance in mind: enabling continuous background ventilation while moderating the temperature of incoming air. By integrating ventilation with thermal performance, rather than treating them as competing requirements, this approach supports healthier indoor environments without compromising comfort or increasing energy demand.