Find and reduce draughts without blocking ventilation

Give the draught an address

A cold ankle beside the sofa is a useful starting point, but a poor shopping list. Before buying rolls of sealing strip, identify the exact joint where air enters and decide whether that opening has a job. Your first purchase may be a replacement window gasket; it may also be nothing until someone identifies a wall vent.

Make a sketch of the uncomfortable room. Mark the chair or bed where you notice the problem, each outside window and door, and every visible grille. Give suspected leaks precise names: “left opening window, lower hinge corner” is more useful than “front room”. Leave space beside each name for a decision and a follow-up result.

Gather a torch, notebook, tissue, ordinary paper, ruler and tape measure. Keep this inspection at floor level, with fittings intact. You do not need smoke, candles, aerosol sprays, access behind sockets or a trip into the loft. The aim is a short list of accessible faults you can explain.

Mark the openings that must stay open

Before searching for leaks, record the ventilation routes you can identify. Energy Saving Trust's draught-proofing guidance says to preserve extractor outlets, wall vents, window trickle vents and underfloor airbricks. Trickle vents should normally remain open; gaps beneath internal doors allow air to move through the home. Do not add door snakes or seals to those internal gaps.

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Give an unfamiliar opening the status identify before changing. A rectangular hole is not redundant just because no air seems to move through it today. Consult the home's ventilation information, the property manager or a ventilation specialist. If you cannot identify any designed background ventilation, obtain advice before tightening the room.

Fuel-burning appliances add a separate prerequisite. The HSE's domestic gas guidance explains that adequate combustion air and clear flues are essential to prevent dangerous carbon monoxide accumulation. If the room has a gas fire, boiler or other fuel-burning appliance, ask an appropriately qualified appliance engineer whether your proposed sealing affects its air supply before proceeding. In the UK, use a Gas Safe registered engineer for gas appliances; elsewhere, use the locally qualified equivalent. Do not alter appliance vents, flues or chimney openings.

Sketching an arrow between a background inlet and an extract room is a useful reminder to preserve the route. It is not a calculation of ventilation capacity or proof that the system works.

Locate the joint, rather than blaming the whole window

Choose naturally breezy weather when the discomfort is noticeable. Close external windows and doors normally, keeping intended ventilation in its usual operating state. Leave heating and ventilation controls alone. Do not deliberately run every extractor to exaggerate leakage: this inspection uses ordinary conditions.

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Move your hand slowly along accessible window and exterior-door edges. Hold a small tissue strip near a suspect joint without inserting it into any opening. The Pacific Northwest National Laboratory weatherstripping guide describes hand and tissue checks. Compare a suspect corner with another part of the same frame. A cool pane alone does not establish where outside air enters.

Next, look for displaced seals, loose ends, visible daylight at closing edges and debris preventing normal closure. Close and latch the window once, normally, then repeat your observation. If correct latching removes the breeze, record that before deciding anything needs replacing.

For a hinged window or ordinary exterior door that closes freely, use the ENERGY STAR paper check: close it on a strip of paper and gently pull. Test several comparable positions, keeping fingers clear. Easy withdrawal flags a possible weak seal; uneven resistance helps locate it. Do not force a stiff fitting or use the result to claim a measured leakage rate.

Write observations separately from conclusions: “tissue moves at bottom corner” is evidence; “entire window needs replacing” is a purchase decision that the evidence does not yet support.

Sort the map into repair, preserve and refer

Use these decisions to keep the job small. A visibly damaged seal on a freely operating window is a clearer first candidate than a mysterious draught emerging behind a fitted cupboard.

Leave fire doors and their seals to the responsible maintenance provider. For rented property, send the location and photographs to the landlord before applying adhesive or changing fittings. These are useful descriptions of the requested repair, rather than a request to “seal everything”.

Repair one suitable window seal

Proceed only with a sound, accessible window that already opens, closes and locks properly, and whose replacement-seal instructions you can follow without dismantling it. Identify the window make or seal profile first. A photograph, model reference and measurements give the supplier something concrete to match. Leave sliding sashes and unfamiliar gasket systems to a window specialist.

Hypothetical measuring example: an opening sash measuring 600 mm by 900 mm, approximately 24 by 35 inches, has a perimeter of 3,000 mm, or about 9.8 feet. That is a planning length, not a buying specification: establish which edges the manufacturer's system seals, the required profile and the pack's usable length before ordering.

1. Read the replacement instructions before removing anything. Check finish compatibility, preparation requirements and application conditions.
2. Remove only the old seal that the instructions identify as replaceable. Stop if removal needs cutting into the frame, disturbing paint or taking out hardware.
3. Prepare the receiving surface as the window and seal manufacturers specify, and let it dry fully. Avoid improvised solvents on an unknown finish.
4. Measure each instructed run, then cut and fit the replacement as directed. For adhesive strips, follow the specified corner treatment and pressing method.
5. Open, close and lock the window gently. The seal should contact its mating surface without needing extra force. Remove or correct the replacement if operation worsens.

PNNL's guide supports dry-surface preparation, measured fitting and checking full closure after installation. Keep a note of the product reference for future repairs. Never bridge a ventilation slot or an unidentified drainage opening with the strip.

Read the room map after one change

Consider this hypothetical sitting room: the occupant feels a breeze at the reading chair, paper slips easily from one corner of the opening window, and an airbrick is visible outside below the timber floor. There is also a gap under the door to the hall.

The window corner goes on the repair list. The airbrick and internal door gap go on the preserve list. Energy Saving Trust explains that underfloor ventilation helps keep timber dry; sealing that outside airbrick would treat a different opening from the one identified at the window.

After a compatible window-seal replacement, repeat the corner check. If the local breeze improves but the chair still feels cold, record both results. Do not call the repair a failure simply because it did not solve every comfort issue. Moving the chair away from the pane may improve comfort while you decide whether further assessment is worthwhile. It does not prove that another gap needs sealing.

Finish with an operation check and a ventilation check

Before putting tools away, confirm that the repaired window opens, closes and locks normally, no loose strip catches, and every marked ventilation opening remains unobstructed. Revisit the same joint in comparable breezy weather. Compare the original observation with the new one, rather than comparing a windy morning with a calm afternoon.

During normal occupancy afterwards, watch for new or worsening persistent window condensation, damp patches or stale conditions. Energy Saving Trust warns that further draught-proofing can harm air quality where ventilation is insufficient. Pause further sealing and request a ventilation assessment if these changes appear. A tissue check cannot certify adequate fresh-air supply.

Escalate earlier for water entry, deteriorating timber, a window that binds, an unexplained opening or a persistent leak whose route is hidden. ENERGY STAR recommends a professional energy assessment to locate hidden leaks and identify safety issues. Give the assessor your annotated room sketch, photographs and replacement details. Ask them to identify the remaining leakage route and check ventilation before recommending more sealing.