Developing an EU energy labelling scheme for windows

A powerful tool to boost the energy efficiency of buildings - Directive 2010/30/EU extends the scope of energy labelling to energy-related products, i.e. products, like windows, that do not directly consume energy, but indirectly affect the energy consumption of a wider system such as a building. It aims to encourage end users’ to make an informed choice and opt for highly energy-efficient products through the provision of accurate, relevant and comparable information.    

The Eco-design and Energy Labelling Working Plan 2012-20141 recognises the energy saving potential of windows and places window products in the priority list of energy-related products for which new energy labelling schemes should be developed.

High-performance glazing technologies can contribute to significant savings in energy and the associated CO2 emissions if the most appropriate glazing is chosen when window are replaced. Determining the energy performance of a window is complex, as several parameters specific to each window must be taken into account. Therefore European consumers need a clear and intelligible tool to inform their choices.

Glass for Europe welcomes the conclusion of the second Eco-Design and Energy Labelling Working Plan and calls on the Commission to launch the preparatory study for windows without further delay. In particular, Glass for Europe invites EU authorities to start designing the energy balance equation that should underpin the EU instrument to be developed.

Key parameters for an EU energy labelling scheme for windows

• The energy performance of a window should take into account the energy balance between heat gain (expressed by the g-value) and heat loss (expressed by the u-value), and should be calculated according to whether the building in which it is to be used is heated only or also air-conditioned.
• Europe will need to be divided into several zones to reflect the variety of climatic conditions.
• The scope of the scheme should be limited to the residential replacement market only.
• Additional parameters such as summer comfort and light transmittance should also be indicated.

Windows have major potential for energy savings

Window products have major potential in terms of energy savings due to the availability of a wide range of energy-efficient glazing and window products, and the low market penetration of such products in Europe today. TNO, an independent Dutch research centre, estimates that currently 86% of Europe’s
windows are equipped with inefficient glazing, of which 44% are still single glazed2. At the same time, there are currently modern glazing solutions available on the market that are up to 8 times more efficient than these outdated glazing. This translates into major potential for energy savings, as quantified by various independent studies:

• Over 100 million tonnes of CO2 could be saved annually in the EU if inefficient windows were replaced by state-of-the-art produts3.
• The estimated energy savings potential from windows in European buildings reaches 785 PJ/year as of 2030 according to the European Commission’s own work plan4.

On average windows remain in buildings for 30 years. Therefore, if a suboptimal option is applied at the time of replacement, it will lock in a significant part of the saving potential associated with that window.
This illustrates the importance of an appropriate consumer information scheme.

Informing consumers by way of energy labelling is the most powerful tool

In view of the current market situation, Glass for Europe is convinced that providing easy information about the energy performance of windows, by way of an adequate policy tool, should be the priority in terms of EU policy for window products. Energy labelling has huge potential to promote the uptake of energy-efficient windows. By providing consumers with simple, relevant and comparable information on the energy performance of each window available on the market, energy labelling acts as a primary driver of market transformation.

Energy labelling incentivises consumers to opt for the most energy-efficient products at the time of window replacement and contributes to removing the least performing windows from the existing stock, particularly if fiscal incentives for window replacement are linked to the label ratings. This positive effect of energy labelling has been verified in each country that opted for this type of market mechanism, even where the scheme is only voluntary. In particular the compulsory British scheme, operated by the BFRC, has resulted in a significant transformation of the domestic replacement window market, with the top rated windows gaining substantially in market share.

Developing an energy label for the right window products

Energy labelling of windows should apply to the residential replacement market only. Indeed, for new buildings a holistic approach covering the whole thermal envelope of the new construction is preferable and already enshrined in EU legislation5.

In the case of window replacement, a distinction needs to be made between residential and tertiary buildings given their different uses and hence different energy consumption patterns. For instance, the energy consumption patterns of a school, a retail building or a hospital largely differ from one another and from residential buildings. The most optimal glazing solution will therefore also differ.

More specifically, the window market for residential replacement is typically a business-to-consumer market where the consumer needs to get accurate and clear information on the relevant properties of the different window products available. In this specific case, the energy labelling of windows is the right instrument to inform consumers and guide them towards the most energy efficient products.

A window’s performance is best assessed by its ‘energy balance’, taking into account the different climatic realities of Europe

The energy performance of a window cannot be assessed solely on the basis of its insulation capacity as is currently the case for other insulation products. Contrary to opaque fabric, windows are energy providers due to daylight and solar heat gain. They can thus have a positive impact on a building’s energy consumption by providing more energy gains than losses. For instance, capturing solar heat gain through windows and facades during the months consumers turn on their heating helps reduce heating needs and the associated energy consumption and CO2 emissions.

Thus, the energy performance of a window is the balance between solar heat gains (expressed by the g-value) and heat losses (expressed by the u-value). The energy balance is specific to each window and depends on the climatic conditions. It is this balance that determines the most appropriate glazing solution for a given window. Accordingly, the energy balance of a window must be the basis to assess its energy performance under the EU energy labelling scheme. The energy balance should be calculated with an equation that factors in the heat gains and heat losses and is weighted by the climatic conditions and window orientations in typical residential buildings.

To provide optimal guidance, Europe will need to be divided into several geographic zones, in order to reflect the range of climatic conditions. The climatic conditions of each zone should be included as parameters in the calculation of the energy balance, with one equation per climatic zone.

Additional parameters for the EU energy labelling scheme of windows

• For non air-conditioned buildings, an indication of summer comfort could be included in the scheme to inform consumers about the performance of windows in preventing overheating in summer. This information is particularly relevant in areas where cooling needs dominate, such as southern Europe, and areas characterised by temperate climates with hot summers, where thermal comfort during summer is a key element in the choice of new windows. There are very efficient glazing products available to limit heat build up and thereby reduce the need for air-conditioning equipment. Consumers may opt to select these options if they are aware of this performance parameter.
• The light transmission factor of the window could also be indicated in the EU energy labelling scheme. Indeed, the light transmission of windows affects the overall energy consumption of a building because of the positive impact of windows on the need for artificial lighting: the higher the light transmission the lower the need for artificial lighting during daytime and the lower the energy consumption. What is more, the provision of daylight within buildings has many positive implications in terms of health, happiness, well-being and the productivity of the buildings’ occupants.6 It could therefore be pertinent for consumers to be informed about the daylight provision capacity of the different windows available on the market.

1 See Recital 7 of Directive 2010/30/EU. Establishment of the Working Plan 2012-2014 under the Ecodesign Directive: Commission working document SWD(2012) 434 final.

2 TNO Built Environment and Geosciences - Glazing type distribution in the EU building stock - TNO Report TNO-60DTM-2011-00338 - February
2011.

3 TNO Built Environment and Geosciences - Potential impact of low-Emissivity glazing on energy and CO2 savings in Europe - TNO Report 2008-DR1240/

B - November 2008.

4 Establishment of the Working Plan 2012-2014 under the Ecodesign Directive: Commission working document SWD(2012) 434 final.

5 Directive 2010/31/EU on the energy performance of buildings prescribes that all new buildings should be nearly-zero-energy as of 2020.

6 David Strong Consulting – The distinctive benefits of glazing: the social and economic contributions of glazed areas to sustainability in the build environment - 2012