How to weatherproof windows and doors?

To weatherproof windows and doors, the most effective first step is applying self-adhesive foam or rubber draught-proofing strips around opening edges, which can cut heat loss by up to 20% per property according to the Energy Saving Trust (Energy Saving Trust, 2026). This simple DIY measure costs around £10–£20 per door or window and can save households up to £60 annually on heating bills.

The right approach depends on whether you have sash, casement, or sliding windows, and whether doors are wooden, uPVC, or metal-framed. For example, brush strips work best on sliding sash windows, while silicone tubes suit casement doors. Draught-proofing is only effective if frames are sound, rotten timber or warped uPVC may need replacement before sealing works properly. The Energy Saving Trust notes that professional draught-proofing for a whole house costs between £200 and £500, depending on property size and window type.

Seal gaps around window and door frames

Gaps between the frame and the wall are a major source of draughts. Use exterior-grade silicone sealant or expanding foam filler for gaps wider than 5mm. For smaller cracks, acrylic caulk is sufficient. The Great British Insulation Scheme closed on 31 March 2026. It funded insulation measures only and never covered windows or glazing. Always seal from the outside for weather resistance, and ensure the surface is clean and dry before application. This can reduce heat loss through walls by up to 15%.

Install secondary glazing or thermal lining

For single-glazed windows, secondary glazing, a clear acrylic or glass panel fitted inside the existing frame, can reduce heat loss by up to 65% according to the Energy Saving Trust (Energy Saving Trust, 2026). DIY magnetic kits cost around £50–£100 per window, while professional installation averages £200–£400 per window. For doors, thermal blinds or heavy curtains with a pelmet can cut draughts by 40–50%. These options are particularly useful in listed buildings where double glazing is restricted.

Check and replace weatherstripping on doors

Door weatherstripping, the rubber or brush seal around the frame, wears out within 5–10 years. Replace it with EPDM rubber for durability or silicone for flexibility. The Energy Performance Certificate (EPC) guidance (2026) notes that poor door seals can reduce a property’s EPC rating by up to 5 points, affecting resale value. For wooden doors, add a threshold seal or draught excluder at the bottom. Annual replacement costs are £10–£30 per door and take under an hour with basic tools.

A worked example

A typical 1930s semi-detached house in Manchester with six windows and two external doors can reduce draughts for roughly £180 using DIY materials. The Energy Saving Trust states that professional draught-proofing for a whole property of this size costs between £200 and £500, but a homeowner can install foam strips, brush strips for the sash windows, and silicone sealant around frame gaps themselves. With annual heating savings of around £60 to £80, the materials pay for themselves in under three years.Glazing is standard-rated for VAT at 20%. The zero rate for energy-saving materials covers insulation, heat pumps and solar panels; HMRC names secondary and double glazing as excluded (VAT Notice 708/6). The Great British Insulation Scheme closed on 31 March 2026. It funded insulation measures only and never covered windows or glazing.

What homeowners often get wrong

The most common mistake is sealing trickle vents or existing ventilation gaps, which can cause condensation and mould inside the home. Here are three frequent errors homeowners make when weatherproofing windows and doors.

1. Sealing trickle vents shut Many people block the small slots above double-glazed windows to stop draughts, but these vents are required by Building Regulations for background ventilation. Blocking them traps moisture indoors, leading to damp walls and potential health risks that cost hundreds to remediate.
2. Using interior sealant on exterior gaps Homeowners often grab standard bathroom silicone for gaps between the window frame and outside wall, but this degrades within months under UV light and rain. Exterior-grade silicone or expanding foam designed for outdoor use lasts over 10 years and prevents water ingress that can rot timber frames.
3. Installing draught strips on warped frames Applying foam strips to a rotten or warped wooden door frame creates a false seal that fails within weeks as the wood moves. Replacing the frame or fitting a door threshold strip first costs more upfront but avoids voiding the warranty on new strips and wasting £15 to £30 on materials.

Quick reference

• Self-adhesive foam strips cost £10 to £20 per window and can reduce heat loss by up to 20% according to the Energy Saving Trust.
• Brush strips are the only effective draught seal for sliding sash windows because they accommodate movement without jamming.
• Gaps between the window frame and wall wider than 5mm require expanding foam filler, not just silicone sealant.
• Professional whole-house draught-proofing for a typical three-bedroom semi-detached home costs between £200 and £500.
• Sealing all draughts without providing alternative ventilation can increase indoor humidity and trigger condensation problems.