The Complete Guide to Resealing Double Glazed Windows

Resealing double glazed windows is a crucial maintenance task that homeowners often overlook until problems become apparent. Double glazing, consisting of two panes of glass separated by a spacer and sealed to create an insulating air gap, provides excellent thermal and acoustic insulation. However, when the seal fails, the benefits quickly diminish, leading to various issues that can affect your home’s comfort and energy efficiency.

The primary purpose of the seal in double glazed windows is to maintain the integrity of the insulating unit. This seal prevents moisture from entering the space between the panes and maintains the inert gas (such as argon or krypton) that many modern units contain for enhanced insulation. When this seal fails, you’ll typically notice condensation forming between the glass panes, reduced insulation properties, and potentially higher energy bills as your heating or cooling system works harder to maintain comfortable temperatures.

Several signs indicate your double glazed windows may need resealing. The most obvious is persistent condensation between the glass panes that doesn’t disappear with weather changes. Other indicators include drafts feeling colder near windows, visible damage to the window frame or seals, difficulty opening or closing windows, and increased outside noise penetration. If you notice any of these symptoms, it’s likely time to consider resealing your double glazed windows.

Understanding why seals fail can help prevent future issues. Common causes include:

• Natural degradation of sealant materials over time (typically 10-20 years)
• Extreme weather conditions causing expansion and contraction
• Poor original installation or manufacturing defects
• Physical damage to the window frame or glass
• Exposure to direct sunlight breaking down sealant materials
• Building settlement affecting window alignment

Before beginning any resealing project, proper preparation is essential. Start by thoroughly cleaning the window frame and glass surfaces. Remove any old, cracked, or failing sealant using a sharp knife or specialized sealant removal tools. Take care not to damage the glass or frame during this process. Once all old sealant is removed, clean the area with rubbing alcohol to ensure proper adhesion of the new sealant. Make sure the surface is completely dry before proceeding.

The choice of sealant is critical for successful resealing of double glazed windows. Not all sealants are suitable for this purpose. Look for these characteristics when selecting a product:

1. Specifically designed for glass and window applications
2. Weather-resistant and UV-stable formulations
3. Flexible when cured to accommodate movement
4. Excellent adhesion to glass, PVC, wood, or aluminum
5. Long lifespan (check manufacturer specifications)
6. Appropriate for your climate conditions

The actual resealing process requires patience and attention to detail. Begin by applying masking tape around the area to be sealed to ensure clean lines. Load your chosen sealant into a caulking gun and cut the nozzle at a 45-degree angle to the appropriate size for your bead. Apply steady pressure while moving the gun along the seam at a consistent speed. The goal is to create a continuous, uniform bead that completely fills the gap without gaps or bubbles. Smooth the bead with a damp finger or specialized tool for a professional finish.

For more severe seal failures where the entire insulating unit is compromised, spot replacement might be necessary. This involves:

1. Carefully removing the glazing beads or stops
2. Taking out the failed double glazed unit
3. Thoroughly cleaning the frame
4. Installing a new sealed unit
5. Applying new sealant around the perimeter
6. Replacing the glazing beads

While many homeowners attempt DIY resealing of double glazed windows, there are situations where professional help is advisable. Consider calling a specialist if:

• The windows are particularly large or difficult to access
• Structural issues are apparent in the window frame
• Multiple windows require attention
• You’re uncomfortable working at heights
• The windows are still under warranty
• Previous DIY attempts have failed

Professional window specialists have access to commercial-grade materials and tools that may provide longer-lasting results. They can also identify underlying issues that might not be apparent to the untrained eye, potentially saving you money on future repairs.

Proper maintenance after resealing double glazed windows can extend their lifespan significantly. Regular cleaning with appropriate products, careful operation without forcing mechanisms, and periodic inspection of seals will help identify potential issues early. Avoid using high-pressure cleaners directly on seals, as this can damage them. Additionally, keep drainage channels clear to prevent water buildup that could compromise seals over time.

The cost of resealing double glazed windows varies depending on several factors. DIY approaches might cost between $50-$200 for materials and tools, while professional resealing typically ranges from $150-$500 per window. Factors affecting cost include:

• Window size and accessibility
• Extent of damage to existing seals
• Type of sealant required
• Local labor rates
• Number of windows needing attention
• Additional repairs needed

Beyond the immediate benefits of eliminated condensation and restored appearance, properly resealed double glazed windows offer substantial energy savings. Studies indicate that failed seals can increase heat loss through windows by up to 30%. Restoring proper sealing can typically reduce this heat loss significantly, potentially saving homeowners hundreds of dollars annually on energy bills, depending on climate and window quantity.

Environmental considerations are another important aspect of resealing double glazed windows. By maintaining properly sealed windows, you reduce energy consumption, thereby lowering your carbon footprint. Additionally, resealing extends the life of existing windows, reducing the need for manufacturing new units and the associated environmental costs of production and disposal.

When planning a resealing project, timing and weather conditions are important considerations. Ideal conditions for resealing double glazed windows include:

1. Moderate temperatures (typically between 40-90°F)
2. Dry conditions with no rain forecast for 24 hours
3. Low humidity to ensure proper curing
4. Minimal wind to prevent debris contamination
5. Adequate daylight for proper visibility

Resealing double glazed windows is not just about addressing current problems but also about preventing future issues. Consider applying protective UV-resistant coatings to south-facing windows, installing window treatments to reduce direct sun exposure, and ensuring proper ventilation in rooms with high humidity to extend the life of your window seals.

In conclusion, resealing double glazed windows is a valuable maintenance task that preserves your home’s comfort, energy efficiency, and aesthetic appeal. Whether you choose the DIY approach or hire professionals, addressing seal failure promptly can save significant money on energy bills and prevent more extensive damage. Regular inspection and maintenance will help identify when resealing is necessary, allowing you to address issues before they escalate into more serious problems requiring complete window replacement.