Ensure the energy rating on your windows is WERS to be confident of true performance (Nat)

Introduction

Installation of incorrect product with incorrect performance will be a costly exercise for builder and owner alike.

The Window Energy Rating Scheme enables windows to be rated and labelled for their annual energy impact on a whole house, in any climate of Australia. A New Zealand variant of WERS, the 'Window Efficiency Rating Scheme', is also available.

To participate in WERS, window makers must obtain energy ratings for their products from a rating organisation that is accredited by the AFRC (Australian Fenestration Rating Council)

The Window Energy Rating Scheme is managed by the Australian Window Association (AWA).

WERS is independent of any one manufacturer and acts as a fair, rigorous and credible system for testing performance claims. WERS-rated windows must meet all relevant Australian standards. The scheme forms part of the quality assurance that smart manufacturers offer their customers. It is all about certified performance.

To realise their full potential, WERS ratings are designed to 'plug in' to NatHERS, Australia's Nationwide House Energy Rating Software. Similarly, the FirstRate house energy rating software from the Sustainable Energy Authority of Victoria will accept data for 'real' windows. This enables designers to 'kick the tyres' of different windows during a rating before final selection is made.

Why you should choose energy rated windows? 

Energy Rating for windows is here to stay. The federal government's Australian Greenhouse Office helped to underwrite WERS as part of its commitment to improving energy efficiency and reducing greenhouse gas emissions from the built environment.

Home resale value, comfort and amenity are improved by the use of high-performance windows. We have moved from an industry traditionally considered as providing a commodity building material to be sold on price alone into offering true consumer goods viewed as performance appliances for energy, noise and security.

WERS conforms to the alternative solution path for energy efficiency within the Building Code of Australia.

What do I look for to understand the performance of a window?

Companies with rated windows can supply a certificate which certifies that the window has been rated by the Australian Window Association. The window's cooling and heating performance is rated separately on a scale of 0 to 10 stars - the more stars, the better. These stars indicate the effect the window will have on the energy performance of the whole house.

Sample energy performance compliance certificate for WERS members.   To ensure products performances insist on a performance certificate.   Product and member information available at website.   For more product information visit: www.wers.net

 What Windows Should I Use Where?

Energy Effecient Windows  

Beautiful windows are possibly the most complex and interesting elements in the fabric of our homes.

They provide light and fresh air, and offer views that connect our interior living spaces with the great outdoors. However, ordinary windows can also represent a major source of unwanted heat gain in summer and significant heat loss in winter.

Today, remarkable new framing and glazing materials have changed the energy performance of windows in a radical way.

Energy efficient windows will make your home more comfortable, dramatically reduce your energy costs and help to create a brighter, cleaner, healthier environment.

Heating

The priority in a heating climate is to retain heat in the home and maximise the use of 'free' solar energy in winter. Heat transfer takes three forms: radiant heat transfer, conducted heat transfer and heat transfer by infiltration of outside air.

In a heating climate (alpine and cool temperate) the best results are obtained from windows that insulate well (low U-value) and admit plenty of free solar energy (high solar heat gain coefficient). In a cold region, large west-facing windows may contribute to short-term overheating in summer, but glazing with a low solar heat gain coefficient must be used with caution on the west because of the energy penalty it causes over the rest of the year.

Mixed

The priority in a mixed climate is to keep heat out of the home, except during a relatively mild winter season, when 'free' solar heat gain and retention of warmth in the house become important. Heat gain or loss takes three forms: radiant heat transfer, conductive heat transfer and heat transfer via air infiltration. Ideally, mixed climates call for strong solar control on east and west windows, but deliberate use of free sunlight admitted by northerly windows. This means different glazing solutions.

In a MIXED CLIMATE (temperate) the best results are obtained from windows that insulate well (low U-value), admit plenty of free solar energy (high solar heat gain coefficient) on the north during cooler months, but limit solar heat gain from the east and west (low solar heat gain coefficient). Ideally, northerly windows should be protected by correctly sized eaves. This will provide protection from summertime heat and glare while still allowing sun penetration in winter.

Cooling

The priority in a cooling climate is to keep unwanted heat out of the home. In order of decreasing importance, unwanted heat gain takes three forms: radiant heat gain, conducted heat gain and infiltration of hot outside air.

In a cooling climate (tropical, subtropical or hot arid) the best results are obtained from windows that limit solar heat gain on all orientations (low solar heat gain coefficient). Although the first two climates are frequently humid while the last one is not, they can all subject the home to the risk of overheating at any time of the year. Good insulation (a low U-value) is also beneficial, especially if the home is air-conditioned.

Sample table of window data provided by product available on the WERS website visit: www.wers.net

Note:   Any advice, recommendation, information, assistance or service provided by the AWA in relation to the above is given in good faith and is believed by the AWA to be appropriate, but is given without liability or responsibility on the AWA's behalf.