Windows

Glazing Options Explained

In New Zealand, all new buildings have double glazing as standard. 

Windows not only add aesthetic looks, light and offer views out of a home. They also are an important part of home heating and cooling costs. According to PennState College of Earth and Mineral Sciences windows loss more heat per square foot of area in winter and gain more heat in summer than any other surface in the home (4).

Here we look at alternative window options to make heating more affordable and keep you comfortable.

What difference do different glazing options make?

 

Though PennState College is in a different country, their research is still valid. In exploring heating costs in a typical house with a window surface area of 15-20% of the external wall area the following results emerged: homes with single glazed windows in aluminium frames cost about 46% more to heat than equal home with double glazed windows and a wood frame. Homes with single glazed tinted windows with an aluminium frame cost 8% more to heat than homes with double glazed windows with a wood frame (4).

The U- Value of windows describes the rate of transfer of heat through a window or any other product (which can be a single material or a composite), divided by the difference in temperature across that structure. The better-insulated a window or product is, the lower the U-Value will be. The quality of manufacture and installation can strongly affect the U-Value. Single glazing often has a U-Value of above 5, new double glazing often has a value of about 1.6 and many new triple glazing units have a U-Value of 0.8 or better.

Additional glazing options:

  • Argon filling

​There is an option for double and triple glazing to have as an addition Argon gas. Argon gas is filled into the gap between the glass panes instead of air. Argon is a better insulator, reducing at double glazing the heat loss by 3-9% (1).

  • Low E-glass 

​Glass panes can also have an additional special film applied. In low emission glass, a thin polyester film with a micro-thin, transparent metal coating is stuck directly to your existing glass to reflect radiant heat - either from outside or inside - which reduces the amount of energy you need to heat or cool your home (2). Low-E glass cuts window heat loss by about 20% to 30%, compared to double glazing without low-E (1)

Keep more heat in window spaces

There are other ways to help you stay warmer, save money by using less power and therefore save natural resources (as over 1500MW annually are still created via gas and coal (3)).Your house can be further protected from temperature loss off your windows by covering your windows via thermal curtains or blinds.

Sources:

(1) Energywise EECA NZ, 'Double glazing', 19.12.2018

(2) Energywise EECA NZ, 'Low-E window film', 19.08.2019

(3) Electricity Authority NZ, 'Electricity in New Zealand', 13.11.2018

(4) PennState College of Earth and Mineral Sciences; 'Windows and heat loss'; Author: Dr. Sarma Pisupati, Professor, Department of Energy and Mineral Engineering, The Pennsylvania State University

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