How to find and seal draughts without blocking ventilation
Draught-proofing can reduce uncontrolled air leakage around opening windows, external doors and attic hatches. SEAI notes that it can improve thermal comfort and reduce heat loss, but it does not improve the window's U-value. The aim is controlled ventilation, not sealing every route by which fresh air enters the home.[1]
Never cover wall vents, trickle vents or air supplies serving gas, oil or solid-fuel appliances. SEAI specifically highlights adequate air supply to combustion appliances and proper ventilation when airtightness is improved.[1][2]
Map the draught before buying seals
On a cool, breezy day, close the window or door normally and feel around opening edges, meeting rails, the letter plate and the frame-to-wall junction. A thin piece of tissue can reveal moving air without using a flame. Mark the locations with low-tack tape and check whether the sash or door closes evenly.
- Leak around an opening edge: a replaceable compression or brush seal may help.
- Gap beneath an external door: consider a correctly sized threshold or door-bottom seal.
- Crack between frame and wall: investigate failed perimeter sealant or movement.
- Cold glass without air movement: this is heat loss, not necessarily a draught.
Preserve designed ventilation
Identify trickle vents, wall vents, extract fans and combustion-air openings before work starts. Clean and operate them rather than sealing them. SEAI advises that ventilation remains important for humidity and indoor-air quality, especially as windows and doors become more airtight.[2]
If a room contains an open fire, stove, gas or oil appliance, or if occupants notice headaches, stale air or persistent condensation, obtain competent ventilation advice before tightening the room further.
Choose a seal that matches the gap
Measure the gap at several points. Self-adhesive foam can suit a consistent small gap; rubber compression seals tolerate repeated closing; brush strips can suit sliding components and some thresholds. Too-thick material can prevent locking, strain hinges or distort a uPVC sash, while a thin seal may never make contact.
Clean and dry the fixing surface, cut neat mitres where needed and test a short section before completing the opening. Keep drainage channels, lock keeps and moving hardware clear.
Adjust hardware only within its limits
Loose handles and visibly displaced keeps may be tightened, but do not randomly turn every adjustment on multipoint locks or tilt-and-turn windows. Photograph original positions. A dropped sash, failed hinge, compressed gasket or bowed door may need parts and alignment rather than additional foam.
Know when the opening needs repair
Use a window or door professional when glass is loose, timber is rotten, locks do not engage, seals are integral to the frame, water enters, or the frame-to-wall joint has opened. Draught-proofing should not conceal decay or rain penetration.
Useful job post: 'Two uPVC bedroom windows in a home in Meath have noticeable draughts along the hinge side. Trickle vents are present and will remain open. The sashes appear slightly dropped and the existing rubber gaskets are flattened; no glass misting or rain leak is visible. Photos show each full window, hinges, handles and gasket. Please quote to inspect alignment, replace compatible seals if needed and confirm secure locking.'
Frequently asked questions
Should I seal trickle vents in winter?+
No. Trickle vents provide designed background ventilation. Clean and operate them; do not treat them as accidental gaps.
Why is a window cold even when I cannot feel a draught?+
Heat can pass through glazing and frames without air leakage. Draught-proofing reduces leakage but does not change the window's insulation value.
Can thick foam damage a window or door?+
An oversized seal can prevent proper closing, load hinges and interfere with locks. Measure the gap and test a short length first.
Who repairs draughty uPVC windows?+
A window repair specialist can adjust hinges and keeps, replace compatible gaskets and inspect failed frame seals without automatically replacing the window.
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