Ventilation regulations affect every building project — new build, refurbishment, or change of use. Getting it wrong means failed building control inspections, non-compliant installations, and potentially unsafe indoor environments.
We design air handling units that meet current and anticipated regulatory requirements. Here’s what you need to know about the regulations governing ventilation in 2026 and how they affect AHU specification.
Part F: Ventilation
Approved Document F of the Building Regulations sets out ventilation requirements for buildings in England. Updated in June 2022, Part F establishes minimum ventilation rates for different building types and occupancy patterns.
For non-domestic buildings — offices, retail, industrial, healthcare — the requirements specify minimum outdoor air supply rates based on occupancy and activity. These rates determine the minimum capacity of your ventilation system and directly influence AHU sizing.
Key requirements include minimum fresh air supply rates per person or per square metre depending on space type, provision for purge ventilation (rapid air change capability for removing pollutants), control of indoor pollutants including CO2, humidity, and VOCs, and adequate extract ventilation for kitchens, sanitary facilities, and process areas.
Part F essentially defines the floor — the minimum acceptable performance. In practice, most commercial projects target higher ventilation rates for comfort and productivity, but Part F compliance is non-negotiable.
Part L: Conservation of Fuel and Power
Part L sets energy performance requirements that directly affect how ventilation systems are designed and specified. The 2021 update (effective June 2022) significantly tightened requirements.
For ventilation systems, Part L introduces maximum Specific Fan Power (SFP) limits — the electrical power consumed per unit of air moved. These limits force designers toward more efficient fans, lower-resistance ductwork, and better system design.
Part L also mandates minimum heat recovery efficiency for ventilation systems above certain airflow rates. Systems handling more than 0.5m³/s must incorporate heat recovery with minimum efficiency levels that vary by system type.
This means that for most commercial AHU installations, heat recovery is now a regulatory requirement rather than an optional efficiency measure. We design all our commercial ventilation systems to meet Part L requirements as standard.
Understanding energy efficiency ratings — SFP values, ErP compliance, and heat recovery efficiency — is essential for specifying compliant systems.
ErP (Energy-related Products) Directive
The ErP Directive establishes minimum efficiency requirements at the product level. AHUs and ventilation units must meet ErP Lot 6 requirements covering fan efficiency, drive efficiency, and heat recovery performance.
ErP compliance is a product-level requirement — the AHU manufacturer must ensure their products meet the applicable thresholds. However, specifiers need to understand ErP because it affects what products are available and how they perform.
We manufacture all our air handling units to exceed current ErP requirements, providing a margin against future tightening of standards.
CIBSE Guidelines
While not legally binding in the same way as Building Regulations, CIBSE (Chartered Institution of Building Services Engineers) guidance represents industry best practice and is widely referenced by designers and building control.
CIBSE Guide A provides recommended comfort criteria including temperature, humidity, and air movement. CIBSE Guide B2 covers ventilation and ductwork design in detail. TM57 addresses integrated school design including ventilation. TM40 covers health and wellbeing in buildings.
These guidelines often exceed Building Regulations minimums and represent what good practice looks like. We design to CIBSE recommendations as standard because meeting minimum legal requirements and providing a good indoor environment aren’t always the same thing.
Indoor Air Quality Standards
Post-pandemic awareness of indoor air quality has driven additional focus on ventilation performance. While not yet fully codified in UK regulations, there’s increasing emphasis on CO2 monitoring as a proxy for ventilation adequacy, enhanced filtration for airborne pathogen control, ventilation rates that prioritise occupant health rather than just minimum compliance, and monitoring and verification of ventilation performance in occupied buildings.
We’re seeing more clients specify AHUs with enhanced filtration, CO2-responsive controls, and monitoring capability — driven by occupant expectations and corporate wellbeing policies rather than regulation alone.
What This Means for Your Project
If you’re planning a building project involving ventilation — whether new build, refurbishment, or system replacement — the regulatory landscape is more demanding than it was five years ago. Higher ventilation rates, mandatory heat recovery, tighter SFP limits, and enhanced air quality expectations all affect system design and cost.
Early engagement with an experienced AHU manufacturer helps navigate these requirements efficiently. We can advise on compliant system configurations, help optimise designs for both compliance and performance, and manufacture units that meet all applicable standards.
Contact us to discuss your project requirements and regulatory compliance.
