What should I be asking when considering retrofit double glazing?
Retrofitting double glazing should be carried out by a skilled professional who can
ensure that appropriate Building and Glazing Standards are followed in completing
the work for you. Here are some things to check in advance of approving the work:
- What will your windows and doors look like when they have been double glazed? Ask
to see the changes in place so that you can check first-hand if the glass area will
change and the overall aesthetics. Most windows should have no reduction in viewable
glass area. Some doors (eg sliding doors) may have a small change. The finished
outcome should be one where the changes maintain or enhance your home's appearance
- and don't just look like an add-on.
- What is the width of the space between the two pieces of glass in the double glazing
unit? This should be at least 10mm and not more than 16mm (the optimal space with
air filled double glazing is 14mm and with argon gas is 12mm). If the space is too
small, the cold will more easily travel through the double glazing from one side
to the other. If the space is too large, then convection currents are set up inside
the double glazing resulting in reduced thermal performance. A 12mm space provides
8% better thermal performance than an 8mm space.
- What is the spacer in the double glazing made of? The material of the spacer makes
a difference to the insulation performance (thermal and noise). The best performing
spacers contain no metal. This is important for both timber and aluminium frames
and will make a noticeable difference for condensation reduction.
- What are the options available that can help address other issues at the same time?
Consider options for improved sound control, reducing fading and enhancing security.
- What is the warranty being offered - on the double glazing and on the workmanship?
Double glazing manufactured by members of the Insulating Glazing Unit Manufacturers
Association (IGUMA) has to meet BRANZ tested standards and comes with a 10-year warranty.
- How long has the company been doing this work (retrofitting double glazing) and are
they members of the Window Association of New Zealand? WANZ (or GANZ) membership
provides you with an assurance of industry standards being met with quality workmanship
and good service. Previous customers can also be a great reference for the quality
of work and service that you can expect to receive.
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