Fire Safety and MVHR Ducting: What Installers Need to Know
As demand grows for airtight, low-energy buildings, MVHR ventilation systems (Mechanical Ventilation with Heat Recovery) are becoming standard in both residential and commercial developments. These systems provide constant, filtered airflow while recovering heat from extracted air, making them a key part of any energy-efficient heating system.
However, where there’s ducting running through multiple rooms, floors and fire compartments, fire safety must always be a top priority. Improperly specified or installed ductwork can compromise compartmentation and allow fire or smoke to spread rapidly through a building. For installers, understanding the relevant fire safety requirements and how to apply them on-site is important.
Read on as we explore the key considerations for fire safety in MVHR installations, from ducting materials and penetrations to dampers, insulation and compliance.
Fire Compartmentation and MVHR Systems
A lot of modern building is divided into fire compartments, designed to contain a fire and smoke within a defined area for a specified period - usually 30, 60 or 120 minutes, depending on the building type and regulations. The moment ductwork penetrates one of these fire-resistant barriers, the compartment’s integrity can be compromised if the system isn’t correctly protected.
An MVHR ventilation system naturally connects different areas of a building, transferring air between them. This makes it particularly important that duct penetrations through fire-rated walls, floors, or ceilings are sealed and protected using approved components. The goal is simple: to allow efficient air movement during normal operation, but also to stop the spread of smoke or flames during a fire.
Selecting the Right Ducting Materials
The choice of ducting material is important when it comes to both fire performance and durability. Rigid metal ducting, such as galvanised steel, is the standard in most commercial buildings because it can maintain structural integrity under high temperatures.
In domestic installations, high-quality plastic ducting systems, such as the fittings that we stock at BPC Ventilation, are often used for their lightweight and easy-fit design. While many plastic ducts are made from flame-retardant materials, it’s important to ensure they meet the relevant fire classifications for the project.
For installations running through or near fire compartments, installers should always follow manufacturer guidance and use certified fire-rated components. In some cases incorporating fire-rated sleeves or collars around plastic ducts may be required to meet current building regulations.
Fire Dampers and Smoke Control for Metal Ducting
One of the most important parts of maintaining fire safety is the fire damper. These devices are designed to automatically close when a fire is detected, usually triggered by heat-sensitive elements or linked to a building’s fire alarm system.
In a commercial MVHR ventilation system using metal ducting, fire dampers are typically installed where ducting passes through a fire-rated wall, floor, or ceiling. Once activated, they seal the duct to prevent flames and smoke from travelling between compartments. Depending on the building type, smoke control dampers may also be installed to prevent smoke spread while allowing some airflow for evacuation routes.
Installers should always ensure that dampers are accessible for inspection and maintenance. It’s good practice to coordinate damper placement with other trades early in the build to avoid later clashes with structural or electrical elements.
Correct Sealing of Penetrations for plastic ducting
Every PVC duct that passes through a fire barrier must be properly sealed using an approved fire-stopping system. This typically includes fire-rated collars, wraps, or intumescent sealants that expand under heat to close gaps around the duct. Using general sealants or non-approved materials is one of the most common and dangerous mistakes on site, as they offer no real protection in a fire. Thankfully, you can rely on BPC Ventilation to find high-quality, regulation-approved ventilation products trusted by professionals across the UK.
On domestic fire rated ceilings, a fire rated air valve can be used and are recommended as standard to 3 story and above properties
The fire-stopping material used must always be tested and certified for the specific duct type and penetration size. Installers should maintain accurate records of the products used, their fire ratings and installation dates, ensuring compliance documentation is available for building control inspections.
Insulation and Condensation Control
Insulation also plays a part in maintaining safe operation when it comes to fire safety and ducting. Ducts that carry warm, humid air through cold spaces can suffer condensation, which over time leads to mould growth and material degradation. In metal ducts, condensation can accelerate corrosion and weaken structural integrity, while in insulated systems, moisture can reduce fire performance.
Using non-combustible, foil-faced mineral wool insulation around ducts not only prevents heat loss but also adds a layer of fire resistance. This approach compliments the MVHR system’s role within an energy-efficient heating system, keeping air temperatures stable and improving overall performance.
Compliance, Testing and Documentation
Fire safety standards affecting MVHR systems are covered under UK Building Regulations, particularly Part B (Fire Safety) and Part F (Ventilation). Installers must check that all components are CE-marked (or UKCA-marked) and that fire-rated elements such as dampers and sealants are third-party tested to BS or EN standards.
Testing should verify not just the operation of the MVHR unit itself, but also the integrity of ductwork seals and the closure performance of fire dampers. It’s crucial to keep thorough records, such as manufacturer certificates, test results and installation photos, as proof of compliance.
Partner With the Right Supplier From the Beginning
The growing focus on airtight, low-energy homes means MVHR systems are now a key part of modern building design. But with this comes the responsibility to maintain strict fire safety standards throughout the installation process.
At BPC Ventilation, our expert team supports installers and homeowners alike in designing and supplying complete, compliant solutions that improve comfort and contribute to a truly energy-efficient heating system. Find out more on our website today.
