Can Double Glazing Stop Condensation on Aluminium Window Frames?

Double glazing can significantly reduce condensation on window glass, but what happens when moisture continues to form around the aluminium frames?

It's a common question for homeowners upgrading older windows in New Zealand, particularly in properties with existing aluminium joinery.

The short answer is that retrofit double glazing can reduce condensation on the glass, but it may not completely eliminate condensation on the aluminium window frames. This is because standard aluminium conducts heat, allowing the frames to become colder than the surrounding indoor air.

At Ryan Double Glazing, we specialise in retrofitting double glazing into existing aluminium windows and doors throughout Tauranga, Mount Maunganui, Papamoa, the Bay of Plenty and Waikato.

Understanding the difference between glass condensation and frame condensation can help you make a more informed decision about upgrading your windows.

Why Does Condensation Form on Aluminium Window Frames?

Condensation occurs when warm, moisture-laden air comes into contact with a surface cold enough for water vapour to turn into liquid droplets.

In many older New Zealand homes, aluminium window frames become particularly cold during winter because aluminium is an effective conductor of heat.

When indoor humidity is high and the outdoor temperature drops, moisture can collect on the inside of the frames.

You might notice:

• Water droplets forming along the bottom of aluminium window frames

• Moisture collecting in window tracks

• Condensation appearing around corners and joints

• Water accumulating on windowsills

• Mould developing around window surrounds

These symptoms can be particularly noticeable in bedrooms, bathrooms and other rooms where humidity levels are elevated.

Does Retrofit Double Glazing Stop Condensation on the Glass?

Retrofit double glazing can substantially reduce condensation on the room-facing glass surface.

A double-glazed unit contains two panes of glass separated by a sealed insulating space, often filled with argon gas.

This construction reduces heat transfer compared with single glazing, helping the inner glass surface stay warmer during cold weather.

When the internal glass surface remains above the dew point of the surrounding air, condensation is less likely to form.

However, the result depends on indoor humidity, heating, ventilation, outdoor temperatures and the type of glazing installed.

Double glazing improves the conditions that cause condensation, but it cannot guarantee condensation-free windows in every situation.

Why Can Aluminium Frames Still Get Wet After Double Glazing?

When existing aluminium windows are retrofitted, the original frames are generally retained.

Although the glass is upgraded, the aluminium frame itself may still conduct heat between the inside and outside of the home.

This process is known as thermal bridging.

A thermal bridge is a part of a building component that allows heat to transfer more readily than the surrounding insulated materials.

In an older aluminium window, the frame can remain colder than the new double-glazed glass.

As a result, you may notice a significant reduction in condensation on the glass while some moisture continues to appear on the frames during cold, humid conditions.

This doesn't necessarily mean the double glazing has failed.

What Is the Difference Between Standard Aluminium and Thermally Broken Aluminium Frames?

Standard aluminium window frames generally contain a continuous metal pathway between the outside and inside surfaces.

Thermally broken aluminium frames incorporate an insulating material between the interior and exterior aluminium sections.

This reduces heat transfer through the frame, helping the inside surface stay warmer.

Thermally broken frames can therefore offer better resistance to frame condensation than conventional aluminium frames under comparable conditions.

However, replacing existing joinery with thermally broken frames is a different project from retrofitting double glazing into the existing aluminium windows.

For homeowners with sound existing joinery, retrofit double glazing can still provide a substantial improvement in comfort without requiring complete window replacement.

Can Low-E Glass Help Reduce Condensation?

Yes. Low-emissivity (Low-E) glass can help reduce condensation on the glass by improving the thermal performance of a double-glazed unit.

Low-E glass has a thin, largely transparent coating designed to reduce heat transfer.

When combined with appropriate glazing components, such as argon gas and warm-edge spacers, it can help maintain a warmer internal glass surface.

However, Low-E glass does not turn a conventional aluminium frame into a thermally broken frame.

It's important to understand that glass performance and frame performance are related but separate considerations.

Do Warm-Edge Spacers Reduce Condensation Around Windows?

Warm-edge spacers can help reduce heat transfer around the perimeter of a double-glazed unit.

The spacer separates the two panes of glass and forms part of the sealed glazing system.

Compared with some traditional metal spacers, warm-edge technology can improve temperatures near the edge of the glass, reducing the likelihood of condensation in that area.

However, the spacer does not eliminate thermal bridging through the surrounding aluminium window frame.

This distinction is important when comparing double-glazing specifications.

How Can You Reduce Condensation on Existing Aluminium Frames?

If condensation remains on your aluminium frames, several practical steps may help.

Improve ventilation

Use extractor fans when showering or cooking, and ventilate rooms appropriately to remove excess moisture.

Maintain consistent indoor heating

Keeping rooms at a more consistent temperature can help prevent interior surfaces from becoming excessively cold.

Reduce indoor moisture

Dry clothes outside or use a vented dryer where practical. Address plumbing leaks and other sources of unwanted moisture.

Monitor indoor humidity

A basic hygrometer can help identify rooms with persistently high humidity. As a general guide, maintaining indoor relative humidity around 40–60% can help manage indoor moisture, although condensation can still occur on sufficiently cold surfaces.

Check window drainage and seals

Blocked drainage channels, deteriorated seals or other window defects can contribute to moisture problems.

If water is entering around a window rather than forming as surface condensation, the cause needs to be investigated separately.

Consider the overall condition of your windows

If the aluminium joinery is badly deteriorated, leaking or no longer functioning correctly, replacing the frames may be more appropriate than retrofitting the glass alone.

Is Retrofit Double Glazing Still Worthwhile If the Frames Aren't Thermally Broken?

For many homeowners, yes.

Retrofitting existing aluminium windows can provide meaningful improvements in thermal comfort, heat retention and condensation resistance on the glass.

It can also reduce the disruption associated with replacing entire window units.

The key is understanding what the upgrade can and cannot achieve.

Retrofit double glazing improves the performance of the glazing system, but retaining conventional aluminium frames means some thermal bridging may remain.

An experienced installer should explain these limitations and recommend a solution appropriate for your home.

Frequently Asked Questions

Why do my aluminium window frames sweat in winter?

Aluminium window frames can become cold enough for moisture in the indoor air to condense on their surfaces. This is more likely when indoor humidity is high and outdoor temperatures are low.

Will double glazing completely eliminate condensation?

Not necessarily. Double glazing can greatly reduce condensation on the glass, but moisture may still form on aluminium frames or other cold surfaces, particularly in rooms with high humidity.

Can you retrofit double glazing into old aluminium frames?

Many existing aluminium windows can be retrofitted with double-glazed units, provided the joinery is suitable. A professional assessment is needed to check the frame condition, glazing capacity and hardware.

Is condensation on double-glazed windows a sign of failure?

Not always. Condensation on the room-facing surface can occur when humidity is high. Condensation trapped between the two panes of a sealed double-glazed unit, however, can indicate a failed seal.

Are thermally broken aluminium frames better for condensation?

Thermally broken frames generally reduce heat transfer through the aluminium, helping interior frame surfaces stay warmer. This can reduce the likelihood of condensation compared with conventional aluminium frames.

Will a dehumidifier help with condensation on window frames?

A dehumidifier can lower indoor humidity, reducing the amount of moisture available to condense on cold surfaces. However, it doesn't change the thermal performance of the window frame itself.

Should I replace my aluminium windows or retrofit double glazing?

If your existing frames are in good condition, retrofitting may be a practical option. If they're damaged, leaking or performing poorly, replacement joinery may be more appropriate. A professional assessment can help determine the best solution.

Get Advice on Retrofit Double Glazing in Tauranga and Waikato

At Ryan Double Glazing, we specialise in upgrading existing aluminium windows and doors with modern double-glazed units.

Our team can assess your existing joinery, explain the glazing options available and help you understand what improvements you can realistically expect.

We work with homeowners throughout Tauranga, Mount Maunganui, Papamoa, the wider Bay of Plenty and Waikato.

If you're dealing with cold windows, excessive condensation or uncomfortable rooms, contact Ryan Double Glazing to discuss whether retrofitting your existing windows is the right solution for your home.

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