How To Draught Proof Windows

Draught proofing your windows is one of the quickest and most effective ways to make your home warmer, reduce your energy bills, and cut down on unnecessary waste. This guide will walk you through simple steps to identify and seal those annoying gaps that let heat escape and cold air in. It's a straightforward DIY task that anyone can tackle, helping you create a cosier, more efficient living space while saving money.

Fast Answer

Key Action: Identify and Seal Gaps
Best Material: Self-adhesive foam or rubber strips for opening windows, caulk/sealant for fixed gaps.

1-2 hours per window Time needed

Easy Difficulty

Don't block essential ventilation Watch out for

Before You Start

Cleaning supplies: A cloth, warm water, and mild detergent for preparing surfaces.
Draught detection tools: A lit candle, incense stick, or simply your hand to feel for air movement.
Measuring tape: To accurately measure window frames for materials.
Scissors or utility knife: For cutting weatherstripping or sealing materials to size.
Caulk gun and sealant: A good quality silicone or acrylic sealant for fixed gaps around window frames. Choose a paintable sealant if you plan to decorate afterwards.
Weatherstripping: Self-adhesive foam, rubber, or brush strips suitable for the type of window (e.g., casement, sash, tilt-and-turn).
Screwdriver: To tighten any loose window fittings or adjust latches.
Putty knife or scraper: If you need to remove old, degraded sealant.
Gloves: To protect your hands from sealants and dirt.

Check first: Ensure your windows close properly and are in good repair before starting. Draught proofing won't fix structural issues, and sealing up areas that are meant for ventilation (like trickle vents) can lead to damp or condensation problems. Always maintain adequate airflow in your home.

Step-by-Step Instructions

1. Identify Where Draughts Are Coming From

Before you can fix a draught, you need to find it. This step is crucial for making sure you're targeting the right areas and not wasting materials. Wait for a windy day if possible, or create a slight vacuum by opening a window on the opposite side of the house for a moment before closing it again.

Take a lit candle or an incense stick and slowly move it around the edges of your closed windows – all sides of the frame, where the glass meets the frame, and around any opening sashes. Watch for any flickering of the flame or wisps of smoke being drawn inwards or outwards. You can also simply use your hand to feel for cold spots or air movement. Mark these areas with a pencil or a piece of masking tape.

Tip: Don't forget to check around the window sill and where the window frame meets the wall, as these are common culprits for hidden gaps.

2. Clean and Prepare the Window Surfaces

For any draught-proofing material to stick and seal effectively, the surfaces must be clean, dry, and free from loose paint, dirt, or grease. Use a cloth dampened with warm water and a mild detergent to thoroughly clean all areas where you plan to apply sealant or weatherstripping. Pay extra attention to corners and crevices.

If there's any old, cracked, or flaking paint or sealant, carefully scrape it away with a putty knife or utility knife. A light sanding with fine-grit sandpaper can help create a smoother surface for better adhesion. Once clean, allow the surfaces to dry completely before moving on. This step is often overlooked but significantly impacts the longevity and effectiveness of your draught-proofing.

3. Seal Fixed Gaps with Caulk or Sealant

Fixed gaps are those areas around your window frame that don't move, such as where the wooden or uPVC frame meets the wall, or where the glass is glazed into the frame itself. These are ideal for sealing with a good quality silicone or acrylic caulk/sealant.

Cut the tip of your sealant tube at a 45-degree angle, making a small opening. Load the tube into your caulk gun. Apply a continuous, even bead of sealant along the identified gaps. Try to maintain a steady pressure and speed. After applying, smooth the bead with a wet finger, a damp cloth, or a specialist sealant tool. This pushes the sealant into the gap and creates a neat, professional finish. Allow the sealant to cure according to the manufacturer's instructions, which can take several hours.

Tip: For a super neat line, apply masking tape along both sides of the gap before applying the sealant. Remove the tape immediately after smoothing the sealant for a crisp edge.

4. Apply Self-Adhesive Weatherstripping to Opening Windows

For windows that open and close (like casement, sash, or tilt-and-turn windows), self-adhesive weatherstripping is your best friend. This material is designed to compress when the window closes, forming a tight seal.

Measure the length of each edge of the window sash that meets the frame when closed. Cut the weatherstripping to these exact lengths. Carefully peel off the backing paper, starting from one end. Press the strip firmly onto the clean, dry surface of the window frame or sash where the draught was detected. Ensure it's positioned so it will be compressed evenly when the window is closed. Work your way along, pressing down firmly to ensure good adhesion, especially at corners. Use different profiles (P-strip, E-strip, D-strip) depending on the size of the gap.

Tip: For very narrow gaps, a thin foam strip is often sufficient. For larger, more irregular gaps, a rubberised 'P' or 'D' section strip offers better compression and durability. Always test closing the window gently after application to ensure it's not too tight.

5. Fit Brush Strips to Sash Windows

Sash windows, with their vertical sliding panes, present unique draught-proofing challenges due to the way they move. Brush strips are specifically designed for these types of windows to allow movement while blocking air flow.

Measure the width of the top, bottom, and meeting rails (where the two sashes overlap). Purchase brush strips designed for sash windows; they often come in various lengths and brush densities. For the top and bottom sashes, fit the brush strips along the rebates that run in the grooves where the window slides. For the meeting rail, fit a brush strip to the bottom edge of the upper sash and the top edge of the lower sash, ensuring they meet and interlock when closed. You might need a small saw or strong scissors to cut the plastic or aluminium carrier to size. Secure them with small screws or the adhesive backing if provided.

6. Check and Adjust Window Fittings

Sometimes, draughts aren't due to gaps in the frame, but simply because the window isn't closing tightly enough. This is common with older windows or those with worn hinges or latches.

Inspect all hinges, latches, and locking mechanisms. Are they loose? Do they fully engage? Use a screwdriver to tighten any loose screws on hinges or stays. For casement windows, some hinges allow for adjustment to pull the sash tighter into the frame. For uPVC windows, you might find adjustable 'mushroom cams' on the locking points that can be turned with an Allen key to increase compression against the frame seals. Ensure that when the window is latched or locked, it feels secure and doesn't rattle or move when pushed.

Tip: Lubricating hinges and locking mechanisms with a silicone spray can improve their operation and help ensure a tighter close.

7. Re-check for Draughts and Monitor

Once all your draught-proofing materials are in place and any sealants have cured, it's time for a final check. Repeat the candle or incense stick test around all your draught-proofed windows. This will help you identify any areas you might have missed or where the application wasn't entirely effective.

Don't be disheartened if you find a few small spots; simply re-apply or add more material as needed. Over the next few days and weeks, pay attention to the warmth of your room and your energy usage. You should notice a significant improvement in comfort and potentially lower heating bills. Regularly inspect your draught-proofing materials, especially after extreme weather, to ensure they remain intact and effective.

Quick Reference

Situation	Use this	Why
Fixed gaps between frame and wall	Caulk or silicone sealant	Creates a permanent, airtight barrier for non-moving parts.
Gaps around opening window sashes	Self-adhesive foam or rubber strips	Compresses when the window closes, forming a seal, but allows opening.
Gaps in sliding sash windows	Brush strips	Allows sashes to slide freely while blocking airflow effectively.
Loose latches or rattling windows	Tighten screws, adjust fittings	Ensures the window closes securely, pulling the sash tightly against the frame.
Small cracks in glazing putty	Glazing sealant or putty repair	Prevents draughts directly through the glass-to-frame joint.

Common Problems When You Draught Proof Windows

Sealant peeling or not sticking:
Fix: This usually happens if the surface wasn't clean and dry enough. Scrape off the old sealant, thoroughly clean and dry the area, then reapply. Using a suitable primer for very porous surfaces can also help.
Window is stiff or hard to close:
Fix: You've likely used weatherstripping that is too thick for the gap. Remove the thick strip and replace it with a thinner profile foam or rubber strip. Test the window closure before firmly pressing the full length of the strip.
Draughts are still present after application:
Fix: Go back to step 1 (Identify Draughts). You might have missed a spot, or the material applied isn't quite right for the specific gap size. Sometimes, a draught can originate from a different part of the window, like the glazing itself or deeper within the wall structure.
Condensation or damp appearing after draught proofing:
Fix: While draught proofing helps with warmth, sealing up a room too much without adequate ventilation can lead to moisture build-up. Ensure you haven't blocked any trickle vents or existing airflow. Consider introducing other forms of ventilation, such as regular short bursts of opening windows or using extractor fans in wet rooms (kitchens, bathrooms).
Weatherstripping comes loose or degrades quickly:
Fix: The adhesive might be poor quality, or the strip is exposed to too much friction or weather. Opt for higher-quality, durable rubber or silicone strips, especially for frequently opened windows. Ensure the surface is perfectly clean before application. For very exposed windows, consider more robust, mechanically fixed solutions.

Advanced Tips for Draught Proofing Windows

Consider Secondary Glazing Films: For single-glazed windows, a clear, heat-shrink film applied to the inside of the frame can create an insulating layer of air, similar to double glazing. It’s a low-cost, temporary solution that can significantly improve thermal performance. It's often applied for the colder months and removed in spring.
Thermal Curtains or Blinds: While not direct draught proofing, heavy, lined thermal curtains or blinds can add another layer of insulation and prevent heat loss through the glass and around the frame. Ensure they fit snugly around the window recess to trap warm air effectively.
Address Gaps in the Wall Around the Window: Sometimes, draughts originate from gaps *within* the wall structure around the window frame, rather than just the immediate frame-to-wall joint. If you suspect this, you might need to carefully remove architraves or trim to inspect and fill larger cavities with expanding foam or insulation before replacing. This is a more advanced task.
Professional Assessment for Complex Issues: If you've tried all DIY methods and still have persistent draughts, or if you suspect structural issues with your windows, consider getting a professional energy audit or a window specialist to assess the problem. They can offer solutions for complex cases or advise if window replacement is the most cost-effective long-term solution.
Regular Maintenance: Draught-proofing materials don't last forever. Make it a habit to check your window seals annually, ideally before winter. Replace any worn, cracked, or loose weatherstripping and re-apply sealant where needed to maintain peak efficiency.