Flexivent — Specialist MVHR Design, Part F Ventilation Testing & Commissioning
Flexivent provides professional Mechanical Ventilation with Heat Recovery (MVHR) design, supply, installation, and commissioning services across England and Wales. Our NICEIC-certified engineers specialise in whole-house ventilation systems that comply fully with UK Building Regulations Approved Document Part F, delivering measurable energy savings and healthier indoor air quality for new-build homes, retrofits, barn conversions, and self-build projects.
MVHR Ducting Design and Installation
Every MVHR installation begins with a bespoke ducting design. We calculate airflow requirements for each habitable room and wet room using Part F ventilation rates, then model duct runs to minimise pressure drops and noise. Our engineers work with rigid and semi-rigid duct systems from manufacturers including Zehnder, Vent-Axia, and Nuaire, routing supply and extract branches through ceiling voids, service risers, or first-fix wall cavities. Correct duct sizing and routing are critical: undersized ducts increase fan speed and energy consumption, while poorly routed branches create turbulence that reduces heat recovery efficiency below the 90% threshold required for SAP calculations. We provide a full design package, including duct layout drawings, valve schedules, and commissioning flow-rate targets, before any installation begins.
Part F Airflow Testing and Compliance
Approved Document Part F1 of the Building Regulations requires that all new dwellings and material alterations demonstrate adequate ventilation at completion. Flexivent carries out whole-dwelling airflow testing using calibrated anemometers and manometer rigs to measure supply and extract rates at every terminal device. We record results against the system-specific commissioning sheet and provide the Building Control body with a signed commissioning certificate. Our engineers test to the exact flow rates specified in the approved ventilation design, adjusting terminal valves until each room meets its target within the permitted tolerance. This ensures your project passes final inspection without delays.
Heat Recovery Efficiency and Energy Savings
A correctly installed MVHR unit recovers up to 95% of the thermal energy from outgoing stale air, transferring it to incoming fresh air via a counter-flow heat exchanger. This dramatically reduces space-heating demand, especially in airtight dwellings that achieve air permeability results below 5 m³/h/m² at 50 Pa. Flexivent installs and commissions units with Specific Fan Powers (SFP) compliant with Part L requirements, typically below 0.7 W/l/s for balanced systems. We also advise on summer bypass modes, frost protection strategies, and filter maintenance schedules to sustain long-term performance. Homeowners typically see annual heating bill reductions of 25–40% compared with natural ventilation strategies.
Residential Ventilation Systems We Install
Beyond MVHR, we design and install a full range of domestic ventilation solutions. Positive Input Ventilation (PIV) units treat condensation and mould in existing properties by introducing filtered, tempered air from the loft space. Centralised Mechanical Extract Ventilation (cMEV) draws damp air from wet rooms via a single roof- or wall-mounted fan. Decentralised Mechanical Extract Ventilation (dMEV) uses individual continuously running fans in each wet room, meeting Part F requirements without extensive ductwork. We also supply and install intermittent extract fans, cooker hoods, and window trickle vents. Whichever system suits your property, we ensure it is correctly sized, properly installed, and fully commissioned.
Why Choose Flexivent
Our team holds NICEIC certification and is registered with Electrical Safety First, giving you confidence that every installation meets the highest industry standards. As members of the Federation of Small Businesses, we combine professional-grade engineering with the personal service and accountability of a specialist firm. We carry out airflow testing, system balancing, and Building Control sign-off as part of every project, so there are no loose ends when the job is done.
Contact Flexivent
For a free, no-obligation ventilation quote, call us on 07725 722 132 or email info@flexivent.co.uk. We operate from Tibberton, Gloucestershire (GL19 3AJ) and cover projects across England and Wales. Our typical response time is within 24 hours.
Managed by David Richards — Director & NICEIC Certified Ventilation Engineer (Flexitest Ltd). Page updated: August 2026. All testing complies with UK Building Regulations Part F1.