Building Regulations Part F (ventilation) UK

Building Regulations Part F sets the legal standards for ventilation in new homes and major renovations in England. The 2026 edition introduced significant changes, moving away from simply requiring extractor fans in kitchens and bathrooms.

The single most important change in Part F 2026 is the shift to whole-dwelling ventilation rates, measured in litres per second (l/s) per person, rather than relying on intermittent extract fans in wet rooms alone. This means the entire home must be ventilated continuously, not just when cooking or showering.

The single most important change in Part F 2026 is the shift to whole-dwelling ventilation rates, not just extractor fans in wet rooms

The 2026 edition of Part F sets mandatory whole-dwelling ventilation rates measured in litres per second (l/s) per person, replacing the previous reliance on intermittent extract fans in kitchens and bathrooms alone (HM Government, Approved Document F: Ventilation, 2026 edition, Section 1.1–1.3). These rates are based on the number of bedrooms in the dwelling, not the floor area, which directly affects how much ventilation is required in a home. The change aims to reduce indoor air pollutants and moisture build-up, particularly in increasingly airtight homes, but it also means higher upfront costs for compliant systems.

The cost of a compliant Part F ventilation system in 2026 from £800 to £4,500 installed

A basic system of intermittent extract fans in each wet room (kitchen, bathroom, WC) costs roughly £800–£1,200 installed, but this only meets Part F if the dwelling’s whole-dwelling rate is low, such as in a 1-bedroom flat (Energy Saving Trust, Domestic Ventilation Systems: Cost and Performance, 2025 update). A continuous mechanical extract ventilation (MEV) system costs £1,500–£2,800 installed, including ductwork and a central fan unit. A mechanical ventilation with heat recovery (MVHR) system, which is required for very airtight homes with an air permeability below 3 m³/h·m² at 50 Pa, costs £2,500–£4,500 installed, depending on system size and duct complexity (MCS, Ventilation System Cost Survey, 2026).

Quick numbers Part F ventilation costs, savings, and payback in 2026

Source: Energy Saving Trust, Ventilation and Heat Recovery, 2026; DESNZ, Domestic Energy Efficiency Cost Data, 2026 release. Payback for MEV and MVHR is calculated against the cost of intermittent fans, using gas heating at 7p/kWh.

The direct answer Part F 2026 requires a whole-dwelling ventilation rate of 0.3 l/s per m² of floor area, or a minimum of 13 l/s per bedroom, whichever is higher

This is the plain-English rule. For a 3-bedroom house of 80 m², the whole-dwelling rate is 0.3 × 80 = 24 l/s, but the bedroom-based minimum is 3 × 13 = 39 l/s, so the higher figure of 39 l/s applies (HM Government, Approved Document F: Ventilation, 2026 edition, Table 5.1 and Section 5.3). The required rate must be maintained continuously when the dwelling is occupied, not just when wet rooms are in use. Each habitable room, including bedrooms, living rooms, and dining rooms, must have a minimum background ventilator of 8,000 mm² equivalent area, or a continuous supply rate of 0.3 l/s per m² of floor area.

How to verify your installer meets Part F MCS certification is mandatory for MVHR, and all systems must be commissioned by a competent person

For MVHR systems, the installer must be MCS-certified for ventilation under MCS 022 to certify compliance with Part F and Building Regulations (MCS, Installation Standards for Ventilation, 2026). For MEV or intermittent fan systems, the installer must be registered with a competent person scheme such as NICEIC or NAPIT in the domestic ventilation category if the work is not subject to building control approval (GOV.UK, Competent Person Schemes, 2026). All systems must be commissioned using a Part F-compliant commissioning checklist, including airflow measurements at each terminal, and the results must be left with the homeowner.

The payback is real MVHR saves 1,200 kWh per year in a typical 3-bed home, but only if the home is airtight

MVHR recovers heat from extracted air and transfers it to incoming fresh air, reducing the heating load by 1,200 kWh per year in a typical 3-bedroom semi-detached home with an air permeability of 3 m³/h·m² (Energy Saving Trust, Mechanical Ventilation with Heat Recovery, 2026). At current UK gas prices of 7p/kWh, this saves £84 per year on heating, giving a simple payback of 3–4 years on the additional cost over MEV. However, MVHR only achieves this saving if the home is airtight below 3 m³/h·m². In a leaky home, the heat loss from uncontrolled infiltration makes MVHR less effective (DESNZ, Heat Loss and Ventilation Performance, 2026). how to improve your home's airtightness before installing MVHR

The hidden cost retrofitting ducts in an existing home can add £1,000–£2,000 to the installation

For new builds, ductwork is installed during construction at minimal extra cost, but retrofitting MEV or MVHR into an existing home often requires boxing in ceiling voids or running ducts through cupboards, costing £1,000–£2,000 more than a new-build installation (Energy Saving Trust, Retrofit Ventilation Systems, 2025 update). The ductwork must be designed to minimise pressure drops and noise, which adds design time and material costs, with rigid ducting preferred over flexible. In homes with solid floors, routing ducts to ground-floor rooms may require raising floors or using surface-mounted terminals, increasing disruption and cost (NICEIC, Ventilation Installation Guidance, 2026). the complete guide to Part L building regulations for airtightness