At a glance
Draught proofing is consistently rated by energy efficiency experts as the most cost-effective improvement a UK homeowner can make to reduce heating bills. Unlike loft insulation or a new boiler – both significant investments – draught proofing a typical semi-detached house costs between £50 and £200 in materials and can be completed over a weekend with basic DIY skills. The annual saving on heating bills varies by property type and how draughty the house is, but figures of £60 to £150 per year are typical, giving a payback period of well under two years in most cases. In older UK properties – Victorian and Edwardian terraces in particular – the savings can be significantly higher because the construction methods of those periods left numerous unintentional gaps that have never been sealed.
The important caveat that applies to all draught proofing work is that ventilation must be maintained. Older UK homes rely partly on uncontrolled air movement through gaps and cracks to remove moisture, cooking odours and pollutants. Sealing every gap without providing controlled ventilation in replacement creates a health risk from stale air and accelerates condensation and mould growth. The correct approach is to seal unwanted draughts – gaps around pipes, letter boxes, unused chimneys, gaps under skirting boards – while ensuring kitchens and bathrooms have working extractor fans, trickle vents in windows remain open, and habitable rooms get regular brief ventilation. Done correctly, draught proofing both reduces home energy bills and improves comfort without compromising air quality.
Finding draughts – where to look
The most reliable way to locate draughts is on a cold, windy day with a lit incense stick or a damp hand held near suspected gaps. Draughts make themselves obvious in cold weather but can be invisible in summer. Work around every external door and window frame, across the floor near skirting boards, around the fireplace opening, around pipework where it enters the house through external walls, and around loft hatch edges. In older houses, gaps between floorboards and at the junction of floorboards and skirting boards are often the largest and most overlooked source of cold air from the under-floor void below.
Doors – frames, letterboxes and keyholes
External doors are the biggest single source of draughts in most UK homes and offer the most immediate improvement when sealed properly. The gap between the door and its frame – top, sides and bottom – is addressed with draught-excluding strips. For the sides and top, self-adhesive foam strip is the cheapest option and installs in minutes, but compresses and loses effectiveness within a season or two. A better long-term solution is a brush seal or rubber compression strip fitted into a groove in the door frame or rebate – these last significantly longer and provide a better seal. Measure the gap width carefully before buying as the strips must match the gap to compress correctly when the door is closed.
The door threshold is where most heat loss occurs – the gap between the bottom of the door and the floor. A brush or rubber threshold seal fitted to the bottom of the door closes this gap as the door closes and lifts clear when the door opens, preventing it from dragging. For older external doors with significant warp or gaps that simple sealing cannot address, a replacement or professional refurbishment may be more cost-effective than attempting to seal around an ill-fitting frame. Letterboxes should be fitted with an insulated flap or brush seal on the inner face – these prevent cold air flowing through the slot continuously and also reduce noise and security risk. A simple escutcheon plate covers the keyhole and costs under £5.
Windows and glazing
Sash windows – common in Victorian and Edwardian properties across the UK – are particularly prone to draughts because of the way the two sashes slide past each other. Gaps develop at the meeting rail (where the two sashes overlap in the middle), at the sides where the sashes run in their channels, and at the top and bottom where the sashes meet the frame. Purpose-made sash window draught sealing kits contain brush pile strip for the channels and compression seal for the meeting rail and are available from most builders merchants. Fitting these significantly reduces cold air infiltration without affecting the operation of the window.
For casement windows, check the rubber or foam gasket that runs around the opening frame – these perish and compress with age, losing their sealing function. Replacement gaskets are inexpensive and widely available in the correct profiles for most window systems. Where there is a visible gap between the fixed frame and the wall, a bead of exterior-grade flexible sealant applied with a cartridge gun fills the gap permanently. Do not use rigid filler for this application – it cracks as the frame expands and contracts with temperature changes, and the gap opens again within a season.
Floors, skirting and internal gaps
Gaps between floorboards
Suspended timber ground floors over a ventilated void are a major source of cold air in UK Victorian and Edwardian houses. Gaps between boards can be filled with flexible decorator’s caulk (for small gaps), strips of papier-mache pressed in and sanded flush when dry, or thin timber beading glued into position. Avoid rigid filler which cracks as the boards move with humidity changes. Do not block the air bricks in the exterior wall that ventilate the sub-floor void – these are essential to prevent damp and rot in the floor joists.
Gap between floorboards and skirting
The junction between the floorboard edge and the skirting board is often a continuous gap running around the perimeter of every room in an older house. A bead of flexible decorator’s caulk drawn along this junction and smoothed with a wet finger seals it effectively. Use a paintable caulk in rooms where the skirting is painted – it can be painted over once cured. This single step often produces a noticeable improvement in floor-level comfort in draughty Victorian rooms.
Gaps around pipes and service entries
Wherever a pipe, cable or duct enters the house through an external wall, there is typically a gap between the pipe and the wall that allows cold air in. Fill small gaps with flexible silicone sealant. Fill larger gaps – where gas or water supply pipes enter through the wall – with expanding polyurethane foam, smoothed flush and trimmed once cured. Check around the gas meter box, boiler flue terminal, and any extractor fan duct terminals on external walls.
Loft hatch edges
The loft hatch is where the warm air of the living space meets the cold air of an unheated loft, and an unsealed hatch allows significant heat loss through both conduction and convection. Fit foam compression strip around the perimeter of the hatch frame so the hatch compresses it when closed. Adding rigid insulation board to the top surface of the hatch itself – matching the depth of the loft insulation – completes the thermal seal. This is a quick and inexpensive job that significantly reduces the heat loss to the loft, particularly when combined with adequate loft insulation.
Chimneys and unused fireplaces
An open, unused chimney is one of the largest single sources of heat loss in a UK home – a typical chimney opening allows the equivalent of leaving a window permanently open in the room below. The chimney creates a continuous upward draw of warm room air driven by the stack effect, replacing it with cold air drawn in from elsewhere in the house. Sealing an unused chimney produces a noticeable improvement in room temperature and comfort, often more dramatic than any other single draught-proofing measure.
The most effective and reversible solution is a chimney draught balloon – an inflatable device pushed up into the chimney above the fireplace opening, inflated to fill the flue and deflated and removed if the chimney is ever needed again. The balloon must be positioned above the throat of the fireplace rather than in the opening itself, and a small label hung below it alerts anyone lighting a fire to remove it first. Alternatively, a board cut to the size of the fireplace opening and sealed around the edges with draught strip provides a more permanent closure while still being removable. Never seal a chimney that has a gas fire connected to it – the flue is required for ventilation even if the fire is not used, and this is a safety-critical distinction.
Never seal a chimney connected to a gas appliance. If a gas fire, back boiler or room-sealed appliance is connected to the flue, the chimney must not be sealed – even if the appliance is not currently in use. The flue provides essential ventilation for the appliance and sealing it creates a serious risk of carbon monoxide accumulation. If you are unsure whether an appliance is connected, have the flue inspected by a Gas Safe registered engineer before sealing anything. Only seal chimneys from fireplaces that are confirmed to be entirely disused with no connected appliances.
An effectively draught-proofed home also significantly improves EPC rating, which matters for both the rental market and for property sales – draught proofing is one of the cheapest improvements that assessors recognise as a genuine energy efficiency measure. Combined with internal wall insulation on cold exterior walls, a fully draught-proofed home can achieve a step change in comfort that transforms how it feels to live in during a UK winter.
Common problems and solutions
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