For professionals: draught-proofing in practice

This page is for people who advise on, specify or carry out draught-proofing as part of their work: retrofit assessors and coordinators, energy advisers, surveyors, builders and joiners, housing officers, landlords and conservation officers. It sets out the standards and rules that apply, the risks to manage, and where draught-proofing sits in a wider retrofit.

The room-by-room guides are written for householders, and you’re welcome to point clients to them.

Draught-proofing within a retrofit

Draught-proofing is usually the cheapest airtightness measure in a dwelling, and often the first. Treated in isolation it is low risk. As part of a wider package of insulation and window work, it changes how the building handles air and moisture, and that needs to be designed for.

PAS 2035:2023 sets the framework for whole-dwelling domestic retrofit in the UK and has applied since 30 March 2025. It requires a whole-dwelling assessment covering construction, condition, heritage, services, ventilation and occupancy, and it treats insulation and replacement windows and doors as including airtightness measures. The Retrofit Assessor must record existing fans and background ventilators and check airflow against minimum requirements. Where airtightness improves, the design must make sure ventilation is adequate.

PAS 2030 covers installation, commissioning and handover, and is used alongside PAS 2035. Government-funded schemes, including the Warm Homes: Local Grant, require a PAS 2035 Retrofit Coordinator and TrustMark-registered installers.

Ventilation and building regulations

The principle is simple: reduce uncontrolled air leakage, keep controlled ventilation working.

Replacement windows (Approved Document F, 2021). Where the existing windows have background ventilators, replacements must have them too, no smaller and controllable. Where they don’t, ventilation must be no worse than before; the usual minimum equivalent areas are 8,000 mm² for habitable rooms and kitchens and 4,000 mm² for bathrooms. Historic buildings can be treated more flexibly where full compliance would harm significance or increase deterioration risk, in consultation with the conservation officer.
Draught-proofing existing windows and doors is not covered by the replacement-window rules, but the same logic applies. Seal the opening parts, not trickle vents, and check the dwelling still has adequate background and extract ventilation.
Open-flued gas appliances. Check the room’s air supply before sealing it. BS 5440-2 sets the requirements for air supply to gas appliances; if in doubt, involve a Gas Safe registered engineer.
Solid fuel appliances and open fires need a permanent air supply and an unobstructed flue (Approved Document J). Involve a HETAS-registered installer before changing ventilation in rooms with a stove.
Chimneys. Advise clients that removable chimney blockers must come out before any fire is lit. Permanently closed chimneys should keep some ventilation, top and bottom, to keep the flue dry.

Our householder page Before you start covers the same points in plain terms, and can be shared with clients.

Moisture and traditional buildings

Pre-1919 solid-walled buildings manage moisture by letting it pass through the fabric and evaporate. Draught-proofing on its own rarely upsets that balance; problems tend to come from combining it with impermeable insulation, cement-based repairs or blocked ventilation.

Historic England’s Advice Note 18 (2024), Adapting Historic Buildings for Energy and Carbon Efficiency, considers draught-proofing nearly always permissible, with a negligible effect on significance in most cases. It also treats secondary glazing as generally acceptable.
Use vapour-permeable materials when filling gaps in solid walls: lime mortar, lime-based fillers or sheep’s wool, rather than cement or expanding foam.
Keep sub-floor ventilation working under suspended timber floors. Sealing floorboards is fine; sealing air bricks is not.
Repair before upgrading. Historic England’s view is that traditional windows and doors can almost always be repaired, and draught-proofing works best on joinery that closes properly.
BS 7913:2013, Guide to the conservation of historic buildings, and the Sustainable Traditional Buildings Alliance’s guidance are useful references for a whole-building approach.

Listed buildings and conservation areas

Works that affect the character of a listed building as a building of special architectural or historic interest need listed building consent, and carrying them out without consent is a criminal offence. Whether a particular draught-proofing measure needs consent depends on the building and the method.

Measure	Consent position (listed buildings)
Curtains, blinds, removable chimney blockers, fabric excluders	Not normally needed; nothing is altered
Surface-fixed seals and brush strips on doors and windows	Usually acceptable; often no consent needed, but check locally
Flexible strips or timber slips between floorboards	Not normally needed unless the room’s appearance changes noticeably
Routed-in seals to windows and doors	May need consent, as historic joinery is cut
Secondary glazing	Generally acceptable in principle; consent often needed for fixed installations
Slim or vacuum double glazing in historic frames	Consent needed; may be acceptable where glazing bars and historic glass are kept
Chimney caps, cowls, register plates, removing pots	May need consent

Some councils have made local listed building consent orders that grant consent in advance for defined works. The Royal Borough of Kensington and Chelsea, for example, has orders covering internal secondary glazing and some double glazing in Grade II buildings. Check whether the relevant authority has one before applying.

In conservation areas, internal draught-proofing and secondary glazing don’t normally need permission. Replacing windows can, particularly in flats or where an Article 4 direction applies.

EPCs and RdSAP

RdSAP 10.2, in use since June 2025, records the extent of draught-proofing to windows and doors and the number and type of flues, including open fireplaces and blocked chimneys fitted with ventilators. Two points matter when advising clients:

An open chimney fitted with a damper or baffle plate is now assessed as an open flue, so the damper no longer reduces the modelled ventilation loss, even though it still helps in practice.
Whether a removable chimney blocker is recognised depends on how the assessor records the flue. Agree the treatment with the energy assessor before relying on it for an EPC improvement.

Full draught-proofing of windows and doors makes only a small difference to an RdSAP score. It is worth doing for comfort, condensation control and real-world savings, but it is rarely enough on its own to move a property up a band.

Landlords’ duties

Minimum energy efficiency. Privately rented homes in England must reach EPC band C by 2030.
Carbon monoxide alarms. Since 1 October 2022, landlords in England, private and social, must fit a carbon monoxide alarm in any room used as living accommodation that has a fixed combustion appliance, excluding gas cookers.
Damp and mould. Awaab’s Law has applied to social landlords in England since 27 October 2025, setting deadlines to investigate and fix serious hazards including damp and mould. The Renters’ Rights Act is expected to extend similar duties to private landlords, with dates set in secondary legislation.

Draught-proofing reduces cold and condensation in most homes, but in a dwelling that is already poorly ventilated it can make condensation worse. Check extract fans and background ventilation as part of the same job.

Before you start: a checklist

Is the building listed or in a conservation area? If listed, which measures need consent?
Are there any open-flued or solid fuel appliances? Is their air supply adequate and independent of the gaps being sealed?
Which chimneys are in use, and which can be blocked? Is the client clear about removing blockers before lighting a fire?
Do the wet rooms have working extract fans? Do windows have trickle vents, and are they open?
Is there any existing condensation, damp or mould? Address the cause before tightening the building.
For suspended timber floors: are the air bricks clear and the sub-floor ventilated?
Are carbon monoxide alarms fitted where needed?
Are the doors and windows in good enough repair to seal properly, or do they need easing, rehanging or repair first?
Is any fire door involved? Seals must not stop it closing, and intumescent strips must not be covered.

Using this site with clients

The householder guides cover each part of the home and are kept up to date, with sources and a last-checked date on every page:

If you spot something that’s wrong or out of date, or have experience that would improve a guide, please get in touch.

Sources

Last checked 23 October 2026. This page summarises standards and regulations; it is not legal advice. Check the current documents and the relevant authority before relying on it.