Condensation vs Blown Units; How to Tell the Difference & What It Means for Your Windows

If you’ve noticed misting, fogging, or moisture around your windows, you’re not alone. Many homeowners in Bridgend and South Wales experience this — especially in older uPVC windows.

But not all condensation is the same, and knowing the difference between normal condensation and a blown (failed) glass unit can save you money and help you decide whether you need a repair or replacement.

At Oakwood UPVC Ltd, we’re often called out to diagnose this exact issue, so here’s a simple guide to help you understand what’s going on with your windows.

🌫️ What Is Condensation?

Condensation forms when warm, moist air meets a cold surface. This is normal and can occur on the:

• Inside of your window

• Outside of your window

• Sometimes around frames and seals

This type of condensation does not mean your window has failed. It’s caused by humidity inside the home or temperature differences outside.

Internal condensation (inside your room)

This happens when the inside air is humid — common in kitchens, bathrooms, or poorly ventilated rooms.

Solution: Improve ventilation, use extractor fans, or reduce moisture in the room.

External condensation (outside surface)

This can actually be a sign of a high-performing, energy-efficient window.

Solution: Nothing to fix, it usually clears on its own in the morning sun.

❌ What Is a Blown Window (Failed Unit)?

A blown unit is when the seals around the double-glazed glass fail. This allows moisture to enter between the two panes, something that should never happen.

Signs of a blown unit:

• Mist between the panes

• Water droplets or streaks inside the glass

• Cloudy or foggy patches that don’t wipe away

• A “dirty” look trapped within the glass

• Loss of clarity and insulation

Once the seal has failed, the window loses its thermal efficiency, which can increase heating bills.

🔧 Can a Blown Unit Be Repaired?

The good news is: You don’t need a whole new window frame, just a new glass unit.

At Oakwood UPVC Ltd, we replace:

• Double glazed units

• Toughened units

• Obscure and patterned glass

• Triple glazed units

• Energy-efficient Pilkington or A-rated glass

It’s a quick, clean, and cost-effective fix.

💷 How Much Does It Cost?

Prices vary depending on size and glass type, but in most cases, replacing the glass is far cheaper than replacing the whole window.

We also offer:

• Free quotes

• Quick turnaround

• Professional fitting

• Disposal of old glass

🏡 Serving Bridgend & South Wales

If you're unsure whether your window has condensation or the glass unit has blown, we’re happy to take a look. Often, customers send us a photo and we can diagnose it straight away.

📞 07471 746795🌐 www.oakwoodupvc.co.uk📍 Based in Bridgend — Covering all of South Wales

Need a Quote or Advice?

Message us anytime — we’ll be happy to help. At Oakwood UPVC, we specialise in repairs, replacements, and full installations with honest, reliable service.