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The Green Abode Guide to Window Options

Updated: Jul 5, 2023


Wellington Builders | Design & Architecture Services | Eco-Friendly Design | High Performing Home | Structural Insulated Panels | Energy-Efficient Home

Girl sitting on window ledge, looking outside.

Brrrr! It’s that time of year again! Frosty mornings make it a little harder for us to get out of bed. In addition to piling on multiple layers before braving the outside world, a reality for many of us Kiwis is the morning window condensation wipe down. Quite frankly, it's a pain in the proverbial! Not only is it a waste of precious time and towels, but in our humble opinion, it's downright unhealthy for so much moisture and mildew to be invading our homes.

As a species, we've successfully launched people into space, we've created bionic limbs, we've cured diseases, and so many more incredible feats - so why are we all still tolerating substandard building practices that leave us cold and out of pocket? We think it's high time the weeping windows were a thing of the past!

In a nutshell, condensation is formed when warm air containing moisture meets a cold window surface.

Single-glazed windows have been around in New Zealand since the first prefabricated home was built in 1806. At that time, we settled for single-pane glass windows inside aluminium or timber frames for all our homes. (It was 1806, so I guess we can forgive them!) Thankfully times have changed somewhat in recent years!

Throughout 2007/2008, the Government made double-glazed windows the minimum standard for all new builds. As for triple-glazed windows, which have been around in Europe for many years, we are pleased to report that yes, these too are now also available in New Zealand.

Whether you’re looking to replace the existing windows in your home or are investigating options for your new build, we have the lowdown on all your options, so let's dive in!


Double Glazing

Double-glazing is when there is a space between the inner and outer inner surfaces of the window. The gap between the two panels (sometimes filled with gas - more on that later) reduces the convection of cold and heat and acts as a sound buffer. Double-glazing is a great step up from single-glazing as a window option as well as being less bulky and less expensive than triple-glazing.

Triple Glazing

A step up from double glazing, as there’s another pane of glass involved. This third pane of glass means even more sound and thermal insulation due to the two air gaps. This glazing option costs more than double glazing, but it does provide better condensation control and more heat and sound efficiency. While New Zealand temperatures are not as extreme as in Europe or North America, triple-glazing is a great option to consider if you live in the far south of New Zealand or in a very exposed, unsheltered area.


Let’s move our attention now to frames. If you’re serious about energy efficiency, it pays to consider the type of frames used around the glass panels.


Timber frames are durable and long-lasting. They are also environmentally friendly and have a negative global warming potential. If we have to nit-pick to find a con, they require regular maintenance (oiling or sanding/painting) and usually cost more than other frame options. Timber frames are also susceptible to expansion and contraction due to moisture and temperature fluctuations. Depending on the timber chosen, it can also rot and become weathered in certain climates and locations (such as coastal environments).


The main benefit of aluminium framing is that it is light, strong, durable and low maintenance. Aluminium frames are very stable - they don’t warp, bend or crack and they can even be painted! In addition, they are modern, affordable and won’t rot or grow mould. Aluminium frames are the most common in New Zealand. The biggest downside to aluminium joinery is that it conducts heat which makes it a very poor insulator. (Yes, this means it is prone to the dreaded condensation!) The poor insulation qualities can be mitigated if thermal breaks are included or if the aluminium is combined with another material, such as timber (see below).

Composite Timber-Aluminium

If you prefer the warmth of timber but are still not quite convinced that is the best option for your house, you may wish to consider window frames made from an aluminium/timber hybrid. Don't worry; you're not alone if you've never heard of this option before. It's a clever system, so read on to find out more!

Combining timber with aluminium maximises the strength of both materials and compensates for their weaknesses. The relatively thin aluminium plate is used on the exterior, joined with a moisture barrier to the timber inside the house. This is a good, hard-wearing and low-maintenance option for high-wind and coastal locations and boasts a good variety of timber options.


UPVC stands for 'unplasticized polyvinyl chloride'. UPVC is a rigid type of BPA-free plastic that is strong, durable and weather-resistant. UPVC is a great choice for window frames as it can withstand all sorts of weather conditions, from cold to heat. Unlike aluminium frames, UPVC doesn’t conduct heat which means it provides excellent insulation. By comparison to aluminium, it is over 1,000 times less conductive.

UPVC is an affordable, low-maintenance option that is easy to maintain, is not susceptible to mould or bacterial growth and is also recyclable. It is available in a range of colours and finishes, including woodgrain. This is becoming a more popular option for new window frames in New Zealand, however, about 80-90% of new builds still use aluminium.

NOTE: You might have heard that UPVC is not a suitable option given New Zealand's harsh UV rays. We are not entirely sure where this rumour got started, but we can assure you that even New Zealand's harsh climate is no match for this excellent window framing option.


Fibreglass frames are strong, light, durable and low maintenance. They have cavities that can be filled with insulation, which gives them a superior thermal performance to timber. Fibreglass frames are especially suitable for big windows and triple glazing.


When thinking about windows for your renovation, extension or new build, most people don't think past the glazing and frames. "What else is there to consider?" You might be asking. Believe it or not, there is more to windows than these two components. You might also want to consider technologies such as 'low E', 'thermal spacing' or 'argon gas-filled windows. Below you'll see a brief explanation for these terms (and others), so you can decide if any of them might be right for your project.

Thermally Broken

A thermal break in a window is when a reinforced polyamide strip (a non-metallic, composite, structural material) is fixed between the inside and outside aluminium profile. This strip (often made of plastic) separates the inside from the outside and provides a break so that it is difficult for cold or heat to transfer across the frame. (Note: timber frames are not able to be thermally broken.)

Low E

The “E” is short for Emissivity. Simply put, Low E windows have the ability to reflect thermal energy. Low E glass has a low emissivity coating designed to reflect longwave radiation from the glass itself (from inside or outside the house). This helps to reduce condensation and keep the house warmer in winter.

Thermal Spacing

A thermal spacer is a component that separates the panes of glass in double (or triple) glazed windows. The role of the spacer is to provide a fixed gap between the layers. This gap creates an air-tight cavity within the glass panels, thereby providing excellent insulation.

Argon Filled

Argon is a gas that is pumped inside a double or triple-glazed window to increase thermal efficiency. This slow-moving gas displaces ordinary air, minimising convective currents within the window and reducing heat transfer across the window. It is inexpensive, non-toxic, clear, static and odourless.


The primary reason for tinted glass is to reduce glare, UV and solar heat gain inside the home. Glass is tinted by adding metal oxides during production.


This type of glass is used to promote energy efficiency in the building. Although most commonly used in commercial buildings, some reflective glass has a higher light transmission making it suitable for residential housing. Special coatings are added to the glass during production to reflect and absorb a large proportion of the sun’s direct short-wave radiation.

If you are replacing windows as part of your renovation project or would like to talk to someone about the design of your new home, please Contact Us or give us a call at 0800 368 470 to discuss in more detail your window options. We are passionate about helping our fellow Kiwis live in warmer, drier, quieter homes. Installing thermally efficient windows (that you don't need to wipe down every winter) is one of the many ways you can get on track to achieve this.


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