Draught Proofing: Simple Measures, Significant Impact

Draught proofing remains one of the most straightforward and cost-effective measures in the retrofit toolkit. Poorly sealed air leakage paths waste significant heating energy, particularly in older properties where gaps around windows, doors and penetrations are commonplace. This guide covers practical assessment, specification and installation approaches for housing associations and retrofit coordinators.

Understanding Air Leakage in Existing Housing

Air leakage occurs through gaps, cracks and poorly sealed junctions rather than through solid materials themselves. In pre-1980s properties, construction methods and material degradation create multiple leakage paths:

• Gaps between window frames and masonry openings
• Unsealed service penetrations (pipes, cables, ducts)
• Cracks in mortar joints and render
• Poorly fitted or damaged door seals
• Gaps at skirting boards and wall-floor junctions
• Loft hatch and access panel edges

Air leakage accounts for approximately 15–25% of heat loss in typical older properties. Addressing the most significant leakage paths delivers both energy savings and improved comfort through reduced draughts and cold spots.

Assessment and Identification

Before specifying draught proofing measures, identify the most significant leakage sources. A structured approach saves cost and improves outcomes.

Visual Inspection

1. Walk through properties and look for visible gaps, especially around frames and at junctions
2. Check for daylight visible around closed windows and doors
3. Look for evidence of external exposure: rain staining, debris accumulation, or wind noise
4. Inspect loft spaces for gaps where services penetrate the ceiling
5. Examine basement or crawl spaces for unsealed openings

Tactile Assessment

On cold, windy days, use your hand near suspect areas to feel for air movement. Pay particular attention to:

• Window sill edges and mullions
• Door frames at top, sides and bottom
• Where external walls meet ground floor
• Areas around external pipework and cables

Thermographic Imaging (Optional)

For larger programmes, thermal imaging can identify significant leakage paths and cold bridges that correlate with air movement, though it requires skilled interpretation and cannot measure air flow directly.

Specification and Product Selection

Draught proofing products must suit both the specific location and the building's overall performance strategy.

Common Specifications

Window and Door Seals

• High-quality flexible polymeric seals for moving frames (EPDM or equivalent)
• Brush seals for sash windows with high movement tolerance
• Silicone or acrylic sealant for fixed gaps (non-moving junctions)
• Avoid hard polyurethane in locations subject to movement or vibration

Service Penetrations

• Mastic sealant around pipes and cables where they pass through walls
• Wrap-around closure systems for larger openings
• Mineral wool or fire-rated closures around high-temperature penetrations (boiler flues, etc.)

Fixed Gaps (Masonry, Mortar)

• Lime or cement mortar repointing for external joints
• Low-modulus sealant (not rigid filler) for cracks in rendered surfaces
• Render repair where significant cracking exists

Material Considerations

Choose products that:

• Match the movement characteristics of adjacent materials
• Maintain compatibility with existing finishes (colour, texture)
• Allow for future maintenance or adjustment
• Comply with fire safety standards where applicable (particularly in common areas of multi-unit buildings)

Installation Best Practice

Preparation

1. Clean all surfaces to remove dust, loose paint, algae or debris
2. Allow surfaces to dry fully before sealing (typically 24–48 hours after cleaning)
3. Use primer where recommended by product technical data
4. Mask adjacent surfaces to maintain neat lines and protect finishes

Application

• Apply sealant in a continuous bead with consistent profile (typically 6–8 mm depth)
• Use backer rod in deeper gaps (>6 mm) to maintain depth and prevent sealant from being forced out
• Smooth sealant with wet finger or plastic tool while still soft for better adhesion and appearance
• Allow full cure time before exposing to weather or movement (typically 7–14 days depending on product)

Window and Door Seals

• Remove old seals completely—do not layer new over degraded material
• Install seals on the interior face of external openings to protect them from direct weather exposure
• Ensure seals compress evenly around the entire perimeter
• Test frames for operation after installation—seals must not restrict opening or cause binding

Quality Assurance and Defect Prevention

Common defects arise from poor surface preparation or inadequate curing. Implement simple checks:

• Inspect work within 24 hours of application to catch and remedy any missed areas or poor application
• Verify that seals are continuous and free from gaps, especially at corners and overlaps
• Test window and door operation to confirm no binding or restriction
• Photograph completed work to document baseline condition for future reference

Integration with Broader Retrofit Work

Draught proofing works most effectively when combined with other measures. Coordinate with:

• Insulation upgrades: Seal air leakage paths before insulating to prevent warm, moist air reaching cold surfaces
• Ventilation provision: Ensure background ventilation (trickle vents, extract fans) remains adequate where draught proofing reduces uncontrolled air leakage
• Heating system upgrades: Reduced air leakage improves heating system efficiency and responsiveness

Draught proofing delivers measurable energy savings, improved occupant comfort and reduced heating running costs. Combined with systematic assessment, careful specification and competent installation, it remains a cornerstone of effective, cost-efficient retrofit delivery.