Ventilation Systems

Modern buildings are sealed far tighter than the housing they replaced, and once air leakage has been designed out, ventilation has to be designed back in. We install mechanical ventilation with heat recovery, continuous decentralised extract, positive input ventilation and supply-and-extract systems for new builds, extensions, deep retrofits and office fit-outs around Newbury, Thatcham and Hungerford. Building stock here varies enormously — solid-wall cottages towards Lambourn and Kintbury, 1970s estates, and highly airtight new build off the A34 — so the right answer is rarely the same twice.

Four approaches cover most dwellings, and the choice matters more than the badge on the box. Intermittent extract fans paired with trickle ventilators are the simplest route and remain perfectly legitimate. Continuous mechanical extract runs quietly at a low rate all day and boosts on humidity or occupancy. MVHR supplies filtered fresh air to living spaces while extracting from wet rooms and recovering heat from the outgoing air. Positive input ventilation pushes tempered loft air into the hallway and is often the pragmatic fix for a damp older house.

MVHR only earns its keep in a genuinely airtight building. Guidance commonly puts the threshold around 3 m³/(h·m²) at 50 Pa or tighter; above that, recovered heat leaks straight back out through the gaps in the fabric and you have paid for ductwork you did not need. On a retrofit we look at the air permeability result if one exists, the state of the loft and floor voids, and whether there is a sensible route for duct runs. Where MVHR is not the right call, we say so rather than fitting it anyway.

Approved Document F sets the numbers a system has to hit. Intermittent extract is rated by room: 15 l/s in a bathroom, 6 l/s in a WC, 30 l/s in a utility and 60 l/s in a kitchen, or 30 l/s where the fan sits directly over the hob. Continuous systems work at lower background rates with a boost on top, and the whole-dwelling rate scales with bedroom count. In occupied commercial space the driver is people rather than moisture, with fresh air typically around 10 l/s per person and CO₂ sensors used to prove it.

Installation quality decides whether those design figures are ever achieved. We use rigid or semi-rigid ducting on main runs, keep bends generous, and avoid the concertina flexible hose that quietly halves airflow on so many installs. Duct passing through cold lofts is insulated and vapour-sealed, because warm moist extract air meeting cold metal is how water ends up dripping through a ceiling in January. Terminals are sized so face velocities stay low, and attenuators go in where a run passes between a plant cupboard and a bedroom.

Commissioning is the stage most often skipped and the one Building Control asks about. Every system we install is balanced terminal by terminal and measured with a calibrated instrument, with readings recorded against the design figure for each room and specific fan power checked at the same time. You receive an airflow report showing measured against designed values, and for notifiable work a commissioning notice reaches the building control body within five days of completion. Systems should be rebalanced and remeasured after an extension or a change of use rather than assumed still correct.