In winter, feeling cooler air through an inlet often creates the urge to tape it shut. However, if air is extracted from the house or flat through bathroom and kitchen ducts, a planned way for it to enter is also needed. Closing the supply does not always make the problem disappear: air may start entering through unsuitable places, extraction may decrease or its direction may change. A good solution begins by asking which system the particular inlet belongs to.
Not all inlets use the same controls
Some are manual, others respond to humidity or differential pressure. Similar appearance does not reveal operation. For example, Aereco inlet descriptions present different window and wall versions, including humidity-sensitive ones. This illustrates why the operating procedure must be checked for the particular model, rather than against general advice online.
Find the manufacturer's name, the model or at least a document supplied by the installer. Establish what the lever positions mean. 'Minimum' does not necessarily mean completely closed, and the automatic position is not simply the middle position of the handle. If the information is unavailable, photograph the inlet from inside the room and outside; there is no need to dismantle it while guessing where the adjustment is hidden.
Check the whole air route
An inlet is normally assessed together with the extract points and transfer between rooms. If air enters the bedroom but there is no planned transfer route beneath airtight doors, bathroom extraction may not work as expected. Before altering the opening, also check curtains, the roller-blind box and any thick decorative cover. The airflow route may be blocked somewhere other than the inlet itself.
The pressure difference also matters. A powerful cooker hood running can increase airflow through the supply openings. The PNNL explanation relates airflow both to the opening and to the force driving it. 'There is a draught only when cooking' is therefore a useful diagnostic observation, rather than a reason to blame the window installer automatically.
Cold air should not aim at people
Consider whether a bed, desk or armchair stands beside the inlet. Sometimes discomfort is caused by the furniture layout and curtains altering the intended flow direction. Do not add dense fabric or a homemade filter on your own initiative: the appearance may improve, but the resistance becomes unknown. The manufacturer's intended air direction and a suitable location are more reliable than sealing with adhesive tape.
If the draught comes around the window frame rather than through the inlet itself, that is a separate issue. Adjusting the inlet will not repair a poorly sealed installation detail. In practice, it is useful to mark separately where cold is felt: at the air discharge slot, below the sill or in the frame corners. If necessary, the window-to-wall junction is inspected rather than simply raising the room temperature.
Illustrative example: cold at a desk
Suppose someone works beneath a window in a two-room flat. Bathroom extraction runs and the inlet lies behind a curtain reaching the desk, directing cool air down. Closing it feels better, but bedroom moisture rises by morning. These observations do not diagnose conclusively but support a check plan.
As a first trial, the manufacturer's intended air outlet is cleared and the workstation is moved out of the direct stream. Outdoor temperature, wind and fan setting are recorded. A specialist then checks the supply and extract flows. If the inlet is unsuitable for the calculated demand or local acoustic conditions, an agreed alteration is considered, rather than closing the only air opening for the entire season.
Cleaning without unintended changes
Remove dust from accessible surfaces in accordance with the manufacturer's operating instructions. Do not wash a sensor or acoustic insert merely because the outer plastic component can be washed. Cleaning products can damage sensitive parts, while an incorrectly reassembled component can alter the airflow capacity. Before removing the cover, it is useful to photograph its position and note all settings.
Check the external cover only where it can be reached safely. Do not climb onto a windowsill or lean out of an upper-floor flat's window. If a build-up of insects or an outside blockage is suspected, the work must be organised safely. Replacing grilles or meshes with 'finer' ones must also be agreed: smaller openings do not necessarily improve the whole system's operation.
When to stop adjusting and call a specialist
If adjustment produces whistling, doors begin to move or smells enter from a shared duct, searching for the right lever position by trial and error is not worthwhile. This may indicate a mismatch in the overall airflow route. Note whether the phenomenon recurs with the cooker hood switched off, but do not try to provoke it by lighting a stove or another combustion appliance. These interactions must be assessed by a specialist equipped to do so.
Make the service request specific: you want the balance between supply and extraction checked, not merely to 'stop it blowing'. Otherwise, the result may be very simple: a closed opening and a temporarily improved sensation. Ask for a record of the inlet position left after the check and the conditions in which airflow was measured. These data will be useful when window finishes or the room's use are changed later. If the flat uses a shared system, it is also worth informing its maintenance provider about changes.
What an inlet cannot solve
A supply opening does not remove a building water leak, clean away every indoor pollutant or guarantee an air quantity in any weather. The EPA air-quality guide discusses ventilation alongside control of the pollution sources themselves. If there is smoking nearby, outdoor air is polluted or the home contains a combustion appliance, additional circumstances must be assessed.
Adding an inlet to a heat recovery ventilation system on your own initiative is not always appropriate either. The intended air may bypass the heat exchanger, and the pressure balance may change. First check whether the existing supply is operating correctly. Solutions from separate systems should not be combined mechanically merely because each is individually called ventilation.
Before winter, it is worth having a short reference guide: model, normal position, permitted adjustment, cleaning method and the person responsible for maintaining extraction. An agreement is clearer than a constant argument about who has opened the vent again. If some family members complain of cold and others of stuffiness, this is a good signal to check the system through measurement rather than choose one person's sensation as the only criterion.
For the complete system, see the ventilation services page. In your enquiry, include inlet and room photographs and describe exactly when discomfort occurs.
Information sources
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