Double Glazing Explained

Double Glazing Explained

Should I retrofit or replace my windows – which option is right for me?

There are two factors that influence the decision to retrofit or replace your windows:

  1. Joinery condition
  2. Personal preference


1.  Joinery condition

The Double Glazing Company’s retroGLAZE® system allows most timber and aluminium joinery to be retrofitted with double glazing. In some situations, part or full replacement may be best option, particularly if your existing windows or doors are aged and in poor condition.

Timber joinery condition

New Zealand native timber, including Matai, Rimu and Totara, has traditionally been used in timber windows and doors of traditional homes. Bungalow and Villa homes built from the early 1900’s through to the 1950s were typically built using this timber, which is much harder (and therefore robust) than timber used in joinery manufactured in the 1960s and beyond. The condition of this older joinery is generally sound and well suited to being double glazed. In some cases, there may be a level of deterioration due to moisture ingress over a long period of time. This is more likely where the joinery has not been maintained. The retroGLAZE® window repair systems allow for these traditional windows to have moisture damage removed and treated in advance of being double glazed.

In some cases, more likely in timber joinery constructed from softer wood that has not been well maintained, the window and doors can be unsuitable for retrofitting with double glazing without significant repair or replacement. This is evidenced by extensive rot and joinery falling apart.

Aluminium joinery condition

In New Zealand, aluminium windows become available in the 1960s and became popular into the 1970’s. This first generation aluminium joinery is quite flimsy in comparison to future generations. By the 1980s the quality of aluminium windows and doors had lifted substantially, with the profiles more robust and having the potential to house double glazing.

The early aluminium joinery in New Zealand has a typical life of 45 years. Evidence of end of life could be observed in the failure of joints in the frame (likely resulting in moisture ingress and resulting damage to walls). Older windows may have been installed without metal head flashings (e.g. just using sealants at the top of the window). 

The rubber gasket seals on the outside may have shrunk and hardware (such as window stays and catches or door folding and sliding systems) may no longer be working properly. These are all replaceable and should not be a measure of the overall condition of the windows.

It is important to appreciate that all windows require maintenance over their lifetime.  This may include painting and replacement of seals and hardware which will have a shorter duration of life than the frames and glass.

2.  Personal preference

Once the condition of your joinery has been assessed, and confirmed to be suitable for retrofitting with double glazing, then it comes down to personal preference. Some questions consider are:

  • Do you want to maintain the character of your existing joinery or update it for a more modern look?  This is particularly applicable homes where the windows are a key part of the aesthetic appeal.
  • Are your window frames in need of significant repair or refurbishment, and is this a concern to you?
  • Is budget a determining factor in your decision?

At The Double Glazing Company, we’re all about finding the right double glazing solution for you. When you book an in-home double glazing consultation, we will appraise your windows and take time to understand your requirements. We’ll discuss the range of solutions that can be used to help improve the health and comfort of your home. We’ll also take the time to show you what the changes will look like and answer any further questions you may have.

Whatever your double glazing needs are, you can be confident that we will provide the right retroGLAZE solution for your home

Double glazing questions

Explore our retroGLAZE® solutions

Timber Retrofit

Retain the character & superior insulating properties of timber, upgraded with high performing double glazing.

Aluminium Retrofit

Upgrade your existing single glazed aluminium windows & doors to high performing double glazing.

Replacement windows with new double glazing

Replacement Windows

Refresh and modernise your home with new high performance windows and doors