Separate uncontrolled leakage from designed ventilation
A draught is unwanted, uncontrolled air passing through gaps around frames, floors, hatches or service penetrations. Ventilation is the planned supply and removal of air through background vents, extract fans, air bricks, ducts or a whole-home system. Both can feel like moving air, but sealing them has different consequences. Energy Saving Trust warns that excessive sealing in an already tight home can worsen indoor air quality, so the aim is controlled air exchange rather than an airtight room at any cost.
Make a simple map before buying seals. Mark each external window and door, loft hatch, suspended-floor edge, chimney, fan, trickle vent, wall grille and visible service route. Note where condensation, mould, stale odours or cooking moisture occur, because these are ventilation clues as well as comfort problems. Do not use a candle, smoke source or naked flame to find leakage. A windy, cool day and a careful hand check are safer starting points.
Identify openings that must remain functional
Do not tape over trickle vents, wall ventilators, bathroom or kitchen extracts, underfloor air bricks or transfer openings simply because they admit sound or cold air. Underfloor grilles can help protect timber from moisture; extract fans remove water vapour at its source; background vents provide a predictable route for replacement air. A recirculating cooker hood is not necessarily an extract to outdoors, so confirm where ducts terminate rather than assuming that a noisy fan provides the ventilation the home needs.
Mechanical ventilation needs particular care. A continuous extract system or mechanical ventilation with heat recovery is commissioned as a balanced arrangement with designed supply, extract and internal transfer paths, often including gaps beneath doors. Sealing a terminal, switching the system off or blocking transfer air can undermine that design. Clean user-serviceable filters only as instructed, keep terminals clear and ask a competent ventilation specialist to investigate noise, cold draught complaints or poor flow instead of altering the system by guesswork.
Treat combustion air and flues as a hard safety boundary
Rooms with open fires, open-flued or flueless appliances require special caution. HSE explains that gas appliances need adequate air for combustion and an effective flue to remove products including carbon monoxide. A permanently open combustion-air vent is not spare ventilation to be reduced, baffled or covered. The England Approved Document F FAQ also distinguishes combustion air required under Part J from background ventilation under Part F; one does not automatically replace the other.
Before draught-proofing any room containing a fuel-burning appliance, obtain advice from a competent person for that fuel and appliance. Gas work must be undertaken by an appropriately qualified Gas Safe registered engineer. Oil, wood and coal appliances also need suitable competent assessment. Keep flues clear and appliance access available. A correctly installed carbon-monoxide alarm is an important precaution, but HSE states that it does not replace maintenance, safety checks, ventilation or a sound flue.
Repair ordinary doors, windows and hatches carefully
For an otherwise sound opening, choose a removable seal suited to the gap and movement: a correctly sized compression strip for an opening frame, a brush at a suitable door threshold, a letterbox product designed for the opening, or a compatible perimeter seal at a loft hatch. Test that doors latch, windows drain and emergency exits open normally. Do not paint over vents or fire-door seals, alter a self-closing device, or create a trip hazard at a threshold.
A distorted frame, rotten timber, failed glazing seal, structural movement or water entry needs repair rather than thicker foam. Traditional windows may require materials and detailing that allow movement and drying. Tenants should report defective fabric and obtain permission before fixing products to frames; leaseholders should check responsibilities for windows and entrance doors. In listed buildings or conservation areas, even a small visible alteration can require specialist advice, so use reversible trials and confirm consent before permanent work.
Handle floors, chimneys and service gaps without creating hazards
Small gaps between sound floorboards or at skirtings may accept a flexible, compatible product, but do not block air bricks ventilating a suspended timber floor. Lift boards only when access and services are understood. Hidden cables, pipes and older materials can make drilling, cutting or foaming unsafe. Stop if there is suspect asbestos, damaged wiring, a gas smell, moisture or unknown pipework; arrange the relevant survey or competent trade rather than enclosing the evidence.
An unused chimney may still need a ventilated solution to manage moisture, while an active flue must never be blocked. Confirm that a fireplace is genuinely out of service and have the chimney condition assessed before fitting any removable draught device. Keep electrical fittings, transformers and heat-producing equipment clear in accordance with their instructions. Expanding foam is not a universal answer around cables, flues, fire barriers or moving joints, and concealment can make later inspection harder.
Use a room-by-room sequence and preserve moisture removal
Start with the clearest low-risk leak, then live with the change before sealing the next area. Bedrooms need background air overnight; kitchens, bathrooms and utility rooms need effective extraction during and after moisture-producing activity. Keep internal doors or transfer paths consistent with the ventilation strategy. If windows regularly stream with condensation, mould returns, clothes take unusually long to dry or odours linger, investigate heating, moisture production, insulation and ventilation together rather than adding more seals.
Comfort can improve even when the thermostat reading changes little because fast, local air movement has been reduced. That does not prove a fixed energy saving. Record indoor temperature, humidity, heating hours and meter use, then compare similar weather periods. Portable humidity meters can show trends but are not a building diagnosis. Sudden headaches, dizziness or a carbon-monoxide alarm require the appropriate emergency response, not experimentation with windows or vents.
Check national rules, document the work and reassess
Ventilation and building standards are devolved. Approved Document F and its FAQ describe the England route; Scotland, Wales and Northern Ireland use their own current standards and guidance. Existing homes also differ by age, construction, previous alterations and appliance type, so this guide cannot certify compliance. Ask local building control or a competent assessor where work changes windows, ventilation systems or the building fabric, and obtain landlord, freeholder or heritage consent where the property requires it.
Finish with a labelled record of what was sealed, what remained open and why. Test every fan, vent, window, door and alarm that was affected, retain product instructions and recheck during colder weather. Draught-proofing may reduce avoidable heat loss, but no percentage or payback is guaranteed: weather, heating behaviour, existing airtightness and ventilation needs change the outcome. If comfort improves but humidity or air quality worsens, stop further sealing and have the ventilation strategy reviewed.
Distinguish moving air from cold-surface discomfort before sealing
A place that feels draughty does not always contain a hole. Air cooled against a large pane can fall towards the floor, and a person beside cold glazing or an uninsulated surface can feel uncomfortable through radiant heat exchange even when little outdoor air is entering. Conversely, a narrow frame gap can create a fast local stream that is obvious only in certain wind directions. Observe the sensation on a cool, breezy day without using flame or theatrical smoke. Check whether it follows the opening joint, changes when the latch is engaged, appears below an unobstructed pane, or persists beside a cold wall when the weather is still. Compare the frame, reveal, sill and nearby floor rather than pressing foam into the first place a hand feels cold. Condensation, staining, rot or a distorted opening points towards fabric diagnosis before a thicker seal is chosen. It also prevents a cold-surface complaint from being converted into an indoor-air-quality problem by unnecessary sealing.
Repeat the check with ordinary extract fans and internal doors in their usual positions, because household pressure changes can reveal leakage that calm-room testing misses. Do not switch off, cover or alter designed ventilation to make the sensation disappear, and do not experiment around a combustion appliance or flue. If air is clearly passing through a service joint or failed opening seal, choose a compatible repair that preserves drainage, operation and escape. If the discomfort is mainly downdraught or a cold surface, investigate glazing condition, curtains or blinds positioned safely, insulation continuity and heating distribution instead of choking the nearest vent. Record which weather and operating state produces the problem, then change one low-risk detail and reassess temperature, humidity, odour and condensation as well as comfort. This distinction matters because a successful draught repair stops unintended air movement; it should not be credited with solving a cold bridge, failed window unit or inadequate heating that requires a different intervention.
