UK Ventilation Response installs Mechanical Ventilation with Heat Recovery (MVHR) systems that extract stale humid air from kitchens/bathrooms, recover 90% of heat energy, and supply fresh filtered outdoor air to bedrooms/living rooms. We design duct layouts (rigid/semi-rigid, 75mm-160mm diameter), mount heat recovery unit in loft/utility, install supply/extract grilles in every room—achieving Part F Building Regs compliance (0.3 air changes/hour continuous ventilation without opening windows).
Design survey week 1. Unit + ducts delivered week 2. Loft unit mounted day 1. Ducting installed days 2-4. Room grilles fitted day 5. Commissioned + balanced week 2.
Part F requires continuous ventilation in all habitable rooms (replaced old trickle vents/intermittent extract fans). MVHR achieves this while recovering heat (90% efficiency—if extracting 20°C air and outdoor air is 5°C, supplied air is 18.5°C after heat recovery). Typical whole-house system costs £3,500-5,000 (3-bed semi). Units: Zehnder/Vent-Axia/Nuaire (German/UK brands). Filters: G4 (outdoor air) + F7 (supply)—change every 6 months (£40-60). Electricity: 30-60W continuous draw = £63-126/year at 24p/kWh (but saves £200-300/year heating costs via heat recovery).
📞 0333 600 0993From duct design to Part F compliance certification
Mechanical Ventilation with Heat Recovery for new builds and deep retrofits. Extract from wet rooms (kitchen, bathrooms, utility), supply to dry rooms (bedrooms, living). 90% heat recovery efficiency. Costs £3,500-5,000 for 3-bed house. Zehnder ComfoAir Q (quietest, 18dB), Vent-Axia Sentinel Kinetic (best value, £2,200 trade), Nuaire MVHR-95 (compact). Ducting: 75mm semi-rigid or 160mm rigid (rigid better airflow but needs more ceiling void depth). Installation: unit in loft/utility, ducts run in ceiling voids to each room, supply/extract grilles ceiling-mounted. Airflow: 30m³/h per person (Part F minimum). Filters: G4 outdoor + F7 supply = removes pollen/PM2.5. Running cost: 50W average = £105/year electricity, saves £250/year heating = net £145/year saving.
Building Regulations Part F (Ventilation) requires 0.3 air changes per hour continuous ventilation or purge ventilation via openable windows. MVHR satisfies continuous requirement without heat loss. Calculation: whole house air volume (m³) × 0.3 / 60 mins = minimum airflow (m³/h). Example: 250m³ house needs 75m³/h continuous. Part F also requires: extract ventilation in kitchens (60 litres/sec intermittent or 13 l/s continuous), bathrooms (15 l/s), purge ventilation (openable windows 1/20th floor area). MVHR covers continuous + extract requirements. Commissioning test: airflow measured at each grille, system balanced to within 10% of design flows. Compliance certificate issued. Without Part F compliance, property fails Building Control (can't complete sale, insurance issues).
Proper duct design critical for MVHR performance. Undersized ducts = high air velocity = noise + pressure drop. Duct sizing: 75mm for bedrooms (30m³/h flow), 125mm for living rooms (60m³/h), 160mm for main trunks. Maximum velocity: 3m/s (higher causes whistling noise). Duct layouts: radial (each room has dedicated duct to central unit—best performance, more ducts), trunk-and-branch (main trunk with branches—fewer ducts, slight pressure loss). Bends: minimize (each 90° bend adds 0.5m equivalent length). Insulation: ducts in unheated loft must be insulated (prevent condensation). We use design software (MVHR CAD tools) to calculate pressure drops, optimize layouts, ensure balanced airflow to all rooms.
Heat recovery efficiency measures how much heat energy is transferred from extracted air to supply air. 90% efficiency means: if extracting 20°C air and outdoor air is 0°C, supplied air will be 18°C (0.90 × 20°C temperature recovery). This saves heating costs—you're not venting warm air outside and replacing with cold air (like traditional extract fans do). Calculation: extract 150m³/h at 20°C, outdoor 5°C, heat recovery 90% → supplied air 18.5°C. Heat saved: 150m³/h × 1.2kg/m³ × 1.0kJ/kgK × (20-5)K × 0.90 = 2.43kW continuous. Over heating season (6 months): 2.43kW × 4,380 hours = 10,643kWh saved. At 6p/kWh gas, that's £638/year saving (vs no heat recovery). MVHR electricity: 50W × 8,760 hours = 438kWh/year = £105 cost. Net saving: £638 - £105 = £533/year.
MVHR systems have two filters: G4 (outdoor air, removes large particles, insects), F7 (supply air, removes pollen, PM2.5, fine dust). Filters clog over time—reduces airflow, increases fan power, lowers efficiency. Replacement schedule: every 6 months (twice yearly). Cost: £40-60 for both filters. DIY or professional service (we offer annual maintenance contracts £120/year: filter replacement + duct inspection + fan cleaning + airflow rebalancing). Dirty filter symptoms: reduced airflow from supply grilles, increased fan noise, higher electricity usage (fan works harder). Washable filters exist (G4 can be vacuumed, some F7 are washable) but disposable more hygienic. Always keep spares—if filters fully blocked, system stops working (low pressure alarm triggers, unit shuts down for safety).
MVHR easiest in new builds (ducts planned before plasterboard, ceiling voids designed for duct runs). Retrofit harder: need ceiling void access, may require dropped ceilings/boxing in corridors, or exposed ducts in loft conversions. Retrofit options: (1) Full MVHR if ceiling voids accessible (£4-5k), (2) Decentralized units (room-by-room heat recovery fans, no ductwork—£800-1,200 per room, less efficient but easier install), (3) Positive Input Ventilation (PIV, £600-800—supplies fresh air from loft, dilutes humid air, no heat recovery). We assess property during survey: measure ceiling void depths, identify duct routes, recommend viable solutions. Some properties unsuitable for full MVHR (solid ceilings, no loft access, listed buildings where exposed ducts prohibited)—we advise alternatives honestly rather than forcing unsuitable installs.