After more than 40 years of serving the Christchurch and Canterbury areas, the team at Number One Windows and Doors has encountered every type of window condition—from brand-new installations to units unlikely to survive another winter. While window replacement can seem like a significant undertaking, it almost always saves time, reduces monthly energy costs, prevents further home damage, and, in extreme cases, protects your family from injury.

Recognising the key warning signs is essential for safeguarding both comfort and property value. This guide outlines five clear, easy-to-understand indicators that your windows may be failing—and why addressing them sooner rather than later is a smart decision.

1. Drafts and Poor Insulation

Have you noticed a chilly breeze when you walk past your windows—even when they’re shut? That’s a red flag. Drafts are one of the most common warning signs of bad windows, especially here in Christchurch where the winters can bite. Older windows, particularly those made from timber or with single glazing, tend to lose their insulating power over time.

When should I replace old windows in my house? Well, if your heat pump is working overtime or your curtains flutter when the wind blows, it’s time to consider upgrading to double-glazed aluminium joinery. Not only will you improve your comfort, but you’ll also save money on your energy bills year-round.

2. Rising Power Bills

Another subtle clue your windows are underperforming? Your power bill. If you've noticed that your heating or cooling costs are creeping up and nothing else has changed, your windows might be the culprit.

Replacing old, inefficient windows with energy-efficient options can dramatically reduce heat loss and improve temperature control. This is especially true for Canterbury homes, where the climate can swing wildly from freezing winters to hot, dry summers. Energy efficiency is one of the top reasons why our clients decide it's time for window replacement in older homes.

3. Condensation Between Glass Panes

Double glazing is fantastic—until it fails. One of the most obvious signs your home windows need replacing is if you're seeing condensation or fogging inside the glass. This means the seal has broken and your window is no longer insulating as it should.

If you're seeing misty windows you can't wipe clean, you're not just dealing with an eyesore—you're also losing insulation and potentially setting yourself up for mould problems. In many cases, replacing the entire unit is the best solution, especially when you want long-term value.

4. Difficulty Opening or Closing

Windows should open and shut smoothly. If you have to muscle them open or they stick every time, that’s more than just a nuisance. It could be a sign of warping, rust, or frame deterioration. In the worst-case scenario, this can even be a safety risk in case of emergencies.

Aluminium windows offer excellent durability, and they don’t swell, warp, or rot like timber can. If you're still wrestling with old wooden sashes or corroded steel frames, it might be time to ask: should I repair or replace my windows? Often, the answer is replace—and with quality aluminium joinery that will last.

‍5. Visible Damage or Deterioration

Cracked glass, rotting frames, water stains, mould growth—these are all signs your windows are on their last legs. Even minor damage can reduce insulation, invite moisture in, or attract pests. Plus, broken or warped windows can seriously detract from your home’s appearance and value.

Many of our customers contact us asking whether it’s worth replacing windows in older homes. The answer usually depends on the extent of the damage—but if you’re seeing multiple issues, full window replacement can add immediate comfort and long-term value to your property.

Why It’s Worth Replacing Your Windows

Let’s be honest—new windows aren’t just about looks. They’re a long-term investment in your comfort, your home’s efficiency, and even your safety.

Here at Number One Windows and Doors, we’ve helped hundreds of Christchurch and Canterbury homeowners replace tired old windows with modern aluminium joinery that ticks all the boxes:

• Energy efficiency
• Sound reduction
• UV protection
• Durability
• Modern appearance

We also know that for many clients, it’s not just about insulation or drafts—it’s about building a home that suits their lifestyle. Whether you’re considering a full renovation, adding a conservatory, or just swapping out a few worn-out windows, we’re here to help.

More Long-Term Benefits to Consider:

• Better Security: Modern window systems offer stronger locking mechanisms.
• Reduced Maintenance: Aluminium windows don’t need painting or staining like timber.
• Increased Property Value: New windows are a great selling point if you’re planning to move.
• Compliance and Building Code: Older homes may not meet current standards—window replacement can help.

Should I Repair or Replace My Windows?

We get this question a lot. Sometimes, a repair can buy you a bit more time. But if your windows are older, inefficient, or structurally compromised, replacement is often more cost-effective in the long run.

Still unsure? We’re happy to provide honest, obligation-free advice. No pressure, no hard sell—just real answers based on what we’d do in your shoes.

Let’s Talk About Your Home

At Number One Windows and Doors, we’re not just installers—we’re advisors, designers, and problem-solvers. If you’ve spotted any of these signs your home windows need replacing—or if you’re still not sure—get in touch.

We’ll walk you through your options, help you decide what’s right for your home and budget, and make sure the job is done right.

Serving Christchurch and Canterbury for over 40 years, we’re proud to be your trusted local experts in aluminium window replacement, custom window design, and energy-efficient home upgrades.

Ready to find out if it’s time to replace your windows?

Contact us today for a free measure and quote. Your home—and your wallet—will thank you.