Energy efficiency for windows in New Zealand homes

Windows are the weak link in energy efficiency

- but you can do something about it!


Windows are the weak link in energy efficiency

New Zealand has finally woken up, not only to the need, but also to the benefits of energy efficiency in homes and business buildings. The government has legislated, and is promoting widely, the need for energy efficient homes. But the weakest link in energy efficient homes is the windows. EuroVision has a solution that provides high energy efficient R-value ratings, and also a remarkable return on investment (ROI) for its windows. Proof of this is seen in the accolades received by a recently built home using EuroVision's window system.

Energy Efficiency - the secret to a more comfortable home and less costs

Not only has the leaky home problem raised our awareness of badly built homes, but it has also highlighted the impact that a cold, damp home can have on its occupants. New Zealand could benefit from better health and cost savings in homes and in business buildings if it had better insulation and energy saving standards. It has become so apparent that the government, at long last, has increased the standards for any new home built in New Zealand, and includes measures to decrease the $3.5 billion spent on energy each year.

The Minister of Energy and Resources, Gerry Brownlie, stated in a media statement in September 2009, the government is undertaking a campaign to make New Zealanders aware of the need to make better use of the energy they use in both home and in business. Mr Brownlie said: "As well as saving money, using our energy more wisely improves the health and comfort of our homes, makes for more competitive businesses, protects our environment, and reduces our carbon emissions".

This is on top of the previous government's efforts to tighten up insulation regulations in 2007.

Windows are the weakest link in energy saving

Did you know that the highest loss of energy in any home built in New Zealand since 1978 is through the windows?

According to BRANZ, an un-insulated house loses huge amounts through its roof, walls, floor, and windows.

Here's the figures in a table...

Energy Loss in an un-insulated house
House ComponentEnergy Loss
Roof 30 - 35%
Windows 21 - 32%
Walls 18 - 25%
Floors 12 - 14%
Air Leakage 6 - 9%
Source: BRANZ House Insulation Guide 3rd Edition, 2007

In 1978 it became law to insulate roofs and walls. Since this requirement was implemented, the highest energy loss by far is through windows. The figure has been estimated in the vicinity of 60% loss through windows! Windows are described by the Department of Building and Housing's insulation guide as "the weakest link" when trying to keep heat in during winter.

Insulation and R-Values

You may have heard of "R-values" and wondered what they mean? They are used to compare the insulation value of building materials and walls, windows, roofs and floors in a building. They indicate a measure of the resistance of heat flow, including conduction, convection, and radiation in each of these areas of a building. The higher the R-value, the better the insulation.

The R-values set by the government, that came into effect by late 2008, vary for different parts of New Zealand. New Zealand is broken up into three zones based on climate:

New Zealand Climate Zones
Climate ZoneArea
1 Northern North Island
2 Mid-Lower North Island
3 Central North Island (mountain region) and whole of the South Island

The R-values for those zones are as follows:

R-Values for homes in each zone
 Zone 1Zone2Zone 3
Roof R 2.9 R 2.9 R 3.3
Wall R 1.9 R 1.9 R 2.0
Floor R 1.3 R 1.3 R 1.3
Vertical glazing R 0.26 R 0.26 R 0.26
Skylights R 0.26 R 0.26 R 0.31

You will notice that the values set for windows are much lower than for other areas. That's because of the very nature of windows being predominantly glass. We need windows in our homes for other important reasons, not the least being the need for light within our home, heating from the sun, and ventilation - as well as our desire to have views outside. So it's a compromise.

That's why windows are the "weak link" in insulating a home. It's the weakest point for retaining energy savings in a home. But it need not be so.

Europe has for a long time been at the forefront of energy efficiency, including window design. The cold harsh winters of Europe has meant research, development, testing, and implementation of systems so that European homes have benefitted from energy efficient homes for decades.

The founders of EuroVision had the foresight to see the need for such energy efficient homes in New Zealand, and supply windows and doors that more than meet the subsequently established New Zealand standards. The secret of EuroVision's success is:

  • Thermally broken frames
  • Double (or even triple) glazed windows
  • Low-e and argon
  • Hardy aluminium exterior but wooden internal frames

EuroVision window R-Value tests:

EuroVision windows and doors have been subjected to stringent testing. Testing of the energy efficiency of the EuroVision window is determined by another measure called the U-value. This is actually the inverse of the R-value, or you could call it, a measure of conductivity. Therefore, the lower the U-value, the better the insulation value. Test results have shown a U-value of 1.34, which is the equivalent to an R-value of 0.74. That is well over double the required R-value for the coldest areas of New Zealand!

This extremely high window rating has a flow-on effect into other areas, particularly cost, and more importantly, the all-important "return on investment" (ROI) factor.

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