Window Frames – The Hidden Weak Link in Your Home Keeping It Cold

The conversation around high-performance windows in New Zealand almost always starts with the wrong question: “Should I get double or triple glazing?”. While glazing matters, it’s only part of the equation. The real performance of any window system starts with the frame.

“If you’re only thinking about glazing, you’re already losing performance.”

Why do frames matter more than you think?

Window frames are the structural and thermal barrier between your home and the elements. They must block wind, water, noise, and temperature extremes. In a climate like New Zealand’s, where weather conditions vary wildly and UV exposure is high, the wrong frame can compromise comfort and longevity. Even the most advanced triple-glazed units can underperform when paired with poor framing.

In this article, we break down the most common frame design failures, what to look out for, and which brands are trusted for window frames.

What are the common window frame fail points that kill performance?

The common frame failure points that kill performance include thermal bridging, loss of insulating air pockets, non-welded frames in corners and/or glazing beads, poor drainage, and poor frame support.

What is a thermal bridge?

A thermal bridge occurs when a highly conductive material, like aluminium, allows heat to pass through. In winter, it pulls warmth out of your home, often resulting in cold glass and frames to touch, condensation, and higher energy bills. In summer, it lets heat pour in, making your home uncomfortably hot and difficult to cool down. To combat this, frames must include a thermal break, a low-conductivity material within the frame, which stops heat transfer.

Without this, your window frame becomes a weak link, even if your glazing is high-performance.

The installation method is critical to the performance of the thermal brake. If windows are installed outside the thermal frame and in the cold cavity, the thermal break in the window will be bypassed. This results in windows not achieving their advertised R-value or insulation performance, no matter how well engineered the product itself is.

Glass or frames cold to the touch? = heat loss. Most aluminium joinery in NZ does not contain a thermal break. This creates a direct link to the outside. Additionally, that becomes an area of condensation and mould, creating health hazards.

What are non-welded frames and external glazing beads?

All modern UPVC frames are welded at the corners, creating a rigid, airtight, and watertight structure. In contrast, aluminium frames are mechanically joined, meaning the corners are held together with screws and brackets. While there are various corner joint solutions available, they all share one potential vulnerability: movement over time.

This is problematic in thin or narrow aluminium frames, which lack structural integrity to withstand expansion, contraction, and general wear. As these joints weaken, they become prone to air and water leaks, particularly at the corners. Most aluminium frames on the market are also not deep enough to incorporate an effective thermal break. A shallow frame limits the ability to stop heat from escaping and cold from entering the home, significantly reducing energy performance.

Koffman aluminium frames address this issue by using a multi-cavity system with a 42mm thermal break, bi-component central gasket, 78mm frame depth, and 86mm sash depth. This robust construction ensures structural integrity and high thermal efficiency over the long term.

The Role of Glass Beads

Glass beads secure the glass inside the frame, ensuring stability and maintaining airtight and watertight seals. These components are not welded, so their placement is critical.

In high-performance systems, glass beads are installed internally. However, many aluminium window systems in New Zealand still place glass beads externally, which comes with risks:

Security risk: External beads can be removed from the outside, allowing intruders to remove the glass silently.
Weakened seals: Because external beads aren’t welded and face the elements, they create vulnerable points where water and air can infiltrate.
Reduced performance: Over time, external beading can lead to leaks, condensation issues, and diminished thermal and acoustic insulation.

UPVC windows are designed to open inwards. Some suppliers modify these systems to open outwards, which exposes non-welded glass beads to the outside, and water potentially can leak behind the glass. Materials should be used the way they were engineered to perform. European window systems are designed to be recessed into the thermal envelope of the wall and to open inward for optimal airtightness, water resistance, and long-term reliability.

The Kömmerling Advantage:
Kömmerling uses internal glazing beads, delivering a secure and dry glass seal to the frame seal. This design prevents failure points and locks in long-term performance while allowing simple glass replacement if required.

Why does drainage matter?

Sometimes water ingress happens (for example, you leave your windows open). Your frame needs internal drainage to guide rainwater out, not in. Poor drainage, drainage installed on the wrong side, or blocked will trap moisture, cause water to pool on the inside of the frame, cause condensation, mould, and in worst cases, rot or damage to your home.

The image below depicts a new window that is not draining; water is pooling on the inside of the frame, a clear sign of a failing window.

(Image credit: Reddit diynz)

What is poor frame support?

Poor frame support occurs when a window is not properly supported on all sides of the frame. The typical (incorrect) method to install windows flush with the cladding only supports the bottom of the window frame. This means the top and sides rely on reveals to hold it in place.

Recessed installation provides all-around support to the window frame, ensuring the frame is securely anchored, reducing movement, preventing stress on the joints and improving overall durability, airtightness and weather resistance.

For high-performance windows, full frame support is essential.

What is the best UPVC frame in New Zealand?

The best UPVC frame in New Zealand is Kommerling, German-engineered for performance, durability, airtightness and thermal comfort. At Koffman, we offer 3 Kommerling models.

76AD – Double Seal

76mm construction depth, 5-chamber design
Wide glazing range up to 50 mm for installation of triple and special functional glazing.
Two sealing rubber beads, one internal and one external

Even this base option outperforms most local aluminium on insulation, airtightness, and lifespan.

76 MD – Triple Seal

76mm construction depth
Addition of a central sealing gasket
Wide glazing range up to 50 mm for installation of triple and special functional glazing.

That additional central seal enhances thermal performance by dividing the frame into two separate insulated zones. Perfect for coastal, exposed, or urban homes.

88 MD – Triple Seal

88mm construction depth
7-chamber system
Central seal and full triple seal as standard

88MD offers elite-level performance, meeting Passive House Standards, which is a globally recognised standard focused on ultra-low energy consumption and maximum comfort.

⚠️ Note: Not all UPVC is built for NZ’s UV index. Kommerling is, most rebranded imports are not UV-tested for NZ conditions and may yellow, crack, or warp over time. Kommerling is UV stabilised and tested specifically for NZ.

What is the best aluminium frame in New Zealand?

Procural is the best thermally broken aluminium frame on the market.

Its large 42mm multi-chamber thermal break reduces heat transfer, outperforming local aluminium frames, which often have minimal or no thermal break at all.

Procural also features an internal glazing gasket, expertly designed to enhance both air and water tightness, boosting overall performance in demanding weather conditions.

Engineered in Europe and built to endure New Zealand’s harsh climate, Procural offers the perfect balance of durability, insulation, and modern design.

Multi-chamber thermal break
Triple glazing compatible
Ideal for bifold and large sliders
Requires high-precision install (flashing, foaming, sill support)

Without expert installation and thermal breaks, aluminium is just a cold metal bridge. But done right, it’s unbeatable for large, clean architectural designs.

Which window frames are most energy efficient?

Kömmerling 88MD (Uf = 0.95 W/m²K)
Procural with triple glazing and foam-sealed installation

What should I look out for when choosing window frames?

❌ Local aluminium joinery (standard)	❌ Cheap uPVC systems
– Usually lacks a thermal break. – Cold to touch = conductive. – Condensation issues in winter	– Often thin profiles, poor gasket seals. – Not able to support triple glazing. – Poor sound insulation

How can I test if my windows are failing?

There are several signs that may indicate your windows are underperforming:

Try the touch test: If the frame feels cold to the touch, it likely means the window is not thermally broken, and heat is escaping. Or the window has not been installed recessed, and the line of thermal barrier is not connected.
Condensation or mould: Around the frame, this would suggest poor drainage or thermal bridging, which can lead to moisture buildup.
Noise: If you can hear noise from outside, it’s a sign of poor sealing and glazing or degraded weatherstripping.
Fogging between glass panes: This indicates a broken seal in double- or triple-glazed units, reducing insulation and visibility.

How do you choose the right window frames?

To choose the right window frames, prioritise thermal performance, look at the U-value (lower value = better insulation), quality of seals and number of internal chambers in the frame. Ensure the system is compatible with triple glazing, especially if you’re aiming for high energy efficiency or passive house standards. A well-designed drainage system is also needed to manage moisture and prevent water ingress.

Finally, consider the installation method, including whether the system supports foam sealing and proper sill preparation for long-term airtightness and durability.

Don’t choose windows based on glass alone; the frame is equally critical to total performance
Avoid NZ standard aluminium joinery without a thermal break
Ask if your uPVC is UV-tested for New Zealand

Need expert advice?

Choosing the right frame isn’t just about looks; it’s about ensuring long-term comfort, efficiency, and value.

At Koffman, we supply both Procural aluminium and Kömmerling uPVC systems and help you select the best option based on your project’s design, climate zone, and performance goals.

Whether you’re planning a new build or assessing your current windows, our team will walk you through what matters, from thermal breaks and corner joints to installation. We’ll even compare our systems to standard local frames, so you can make a confident, informed decision backed by clear, technical insight.

Talk to us today, and take the guesswork out of choosing the right window frames.