Experts in Double Glazing and Home Improvements

Energy Efficient Glass

How does Energy Saving Glazing work?

Heat always flows towards the cold. Therefore, window glass without a low-e coating will absorb the heat from your home and radiate it onto the colder outside surface, where it is lost. Low-e glass has a special coating which is a poor radiator of heat and does not allow heat to be transferred to the outside. Instead, the low-e coating actually reflects the heat back into your room.

The interactive demonstration below explains how Pilkington K Glass™ works:

How does Pilkington K Glass™ work?

A Pilkington energiKare™ unit reduces the amount of heat lost through your windows while also allowing more heat/energy from the sun through the glass. This so-called passive solar gain provides additional energy free of charge. A Pilkington energiKare™ unit  is a combination of a product from  either our low-emissivity glass range: Pilkington K Glass™ or Pilkington Optitherm™ combined with Pilkington Optiwhite™ low-iron glass or Pilkington Optifloat™ in a double glazed  or triple glazed unit. The following interactive demonstration shows how Pilkington energiKare™ works:

k glass

More information on Pilkington K Glass™

What is Energy-efficient Glazing?

Energy-efficient glazing is the term used to describe the double glazing or triple glazing use in modern windows in homes. Unlike the original single glazing or old double glazing, energy-efficent glazing incorporates coated (low-emissivity) glass to prevent heat escaping through the windows. This makes the windows highly thermally insulating hence improving the energy efficiency of your home and helping to save money on your heating bills.

Low-emissivity glass (or low-e glass as it is commonly referred to) is a type of energy-efficient glass designed to prevent heat escaping through your windows to the cold outdoors. Low-e glass such as Pilkington K Glass™ Range has an invisible coating which dramatically reduces heat transfer and reflects interior heat back into your room.

Benefits of Energy-efficient Glazing

Installing windows containing energy-efficient double or triple glazed units provides you with many benefits:

  • Improves the energy-efficiency of your home
  • Reduces the amount of energy you use
  • Saves you money on your heating bills
  • More effective than single glazing or standard double glazing
  • Provides you with the quality and reassurance you would expect from a leading brand
  • Manufactured to the highest European quality standards
  • Available from window installers countrywide in a range of frame types

pilkington table

What is low-emissivity glass?

Low-emissivity glass (or low-e glass as it is commonly referred to) is a type of energy-efficient glass designed to prevent heat escaping out through your windows to the cold outdoors.

Unfortunately, many older double glazed units do not contain low-e glass and are therefore not as energy-efficient as they could be. By replacing your existing window glass with low-e glazing, you can improve the energy efficiency of your home, reduce your monthly bills and decrease the size of your carbon footprint.

Pilkington offers a range of single low-emissivity glass products and units.

  • Pilkington K Glass™
  • Pilkington K Glass™ S
  • Pilkington K Glass™OW
  • Pilkington Optitherm™S3
  • Pilkington Optitherm™ S1 Plus
  • Pilkington energiKare™ (This unit is suitable for residential applications)
  • Pilkington Spacia™ (This unit is ideal for older buildings including listed properties)

Why are energy-efficient windows so important?

You’ll probably know that the amount of energy we waste in our homes is directly linked to climate change. And you’ll definitely know about the ever increasing cost of heating your home. But did you know that the glass you use in your windows can help your home be more energy-efficient?

Your windows can have a big impact on the amount of energy you use, the comfort of your home and the cost of heating it – and if you’re thinking of replacing them, look no further than the Pilkington energiKare™ system.

Save money with low-e glazing

By installing low-e windows, you can significantly improve your Window Energy Ratings and reduce the amount of energy lost through your windows by up to 75%!  Considering these figures and the cost of fuel today, it is easy to see why more and more people are opting for A+ rated windows by incorporating low-e glass into their existing window frames.

Benefits of Low-e Glass

Installing windows containing Low-e glass in energy-efficient double or triple glazed units provides you with many benefits:

  • Improves the energy-efficiency of your home
  • Reduces the amount of energy you use
  • Saves you money on your heating bills
  • More effective than single glazing or standard double glazing
  • Provides you with the quality and reassurance you would expect from a leading brand
  • Manufactured to the highest European quality standards
  • Available from window installers countrywide in a range of frame types

Window Energy Ratings

The Window Energy Rating (WER) tells you how energy-efficient your windows are. The rating system is based on a scale of G to A+, with A+ windows being the most energy-efficient. The scheme is similar to those seen on household appliances, white goods and light bulbs.

Benefits of installing energy rated windows:

  • Reassurance of certified scheme approval of the windows
  • Improves the energy-efficiency of your home, reducing the amount of energy you use and helping you to save money on your heating bills
  • Significantly more effective than existing single glazing or standard double glazing
  • Energy Rated Windows are manufactured to European quality standards and meet the requirements for building regulations concerning energy efficiency of homes
    • Since October 2010 legislation demands that windows have a minimum Window Energy Rating of band C
  • Available from window installers countrywide in a range of frame types

Choosing windows incorporating a low-e glass such as a glass from the Pilkington K Glass™ or Pilkington Optitherm™ ranges helps to prevent heat from escaping through the windows, reflecting it back into your home. These energy saving glass products may be incorporated into double glazing unit such as Pilkington energiKare™ units are available countrywide and help achieve the highest levels of Window Energy Rating in almost any frame type.

The labels below are typical of the labels that you should see on your windows. They are supported by registered bodies which audit the window installers;

Certass Thermal Rating 
Register Scheme


Tel. No. 0845 838 8580

BSI Kitemark Scheme 
for WER


Tel. No. 0845 076 5602

British Fenestration Rating Council WER Scheme


Tel. No. 020 7403 9200

Window Energy Ratings were originally launched in March 2004 by the British Fenestration Rating Council (BFRC), an independent government-supported body established to develop and administer a system of Window Energy Ratings in the UK. The BFRC is run by the Glass & Glazing Federation (GGF) the trade body representing many window companies. Visit the GGF website for more information.

Since then both BSI and Certass have set up similar schemes and window companies can gain approval and register with any of these.

What is a Window Energy Rating?

A window’s rating is determined by a formula which takes into account the total solar heat transmittance, the amount of the sun’s heat which can pass through the glass (usually referred to as g-value); the U-value of the whole window (frame and glass combined), how well the window keeps the heat in your home; and the air infiltration through the window seals. To make the Rating standard across all products, a standard window size and configuration is used. The resulting value is then placed into a band on the scale G-A, with A-rated windows being the most energy-efficient. This makes the system of rating windows consistent with other products which have energy performance labels such as those that will be familiar on washing machines, light bulbs and refrigerators.

Who gets a Window Energy Rating (WER)?

A Window Energy Rating and label apply to a whole window (ie the frame and the glass). They do not apply to either the frame or the system or the glass individually. Therefore it is at the point at which all these components come together to produce a whole window that the Rating and label are obtained. Usually it would therefore be the window installer’s product which is rated, although in the case of a factory-glazed window it could be the window manufacturer’s product. Ask your window installer for more information on this.

Pilkington energiKare™ FAQs

It is double (or triple) glazing designed for use in highly energy-efficient windows which incorporates specific glass products from the Pilkington range. It may be made either by our IGU partners or by other companies who have official European standard approval.

Pilkington energiKare™ can be used in windows of any frame material and further assessed to achieve a Window Energy Rating up to band A. This uses a scale of energy efficiency similar to that with which other domestic items are rated. Alternatively it can achieve a U-value of 1.6 or less with both these options qualifying to meet the current Building Regulations for energy efficiency.

There has been widespread news coverage about the escalating costs of energy for the home as well as concern about global warming and damage to our environment so saving energy makes sense. Therefore, when replacing your windows it is a good idea to consider more energy efficient windows so that you can save money on fuel bills and do your bit for the environment.

Every Pilkington energiKare™ double glazing unit is labelled during manufacture. These labels will be on the windows as they arrive at your home but will be removed on final cleaning. Also, you should be given an Installation Certificate stamped and dated by your installer. If you have any problems arising from the fitted windows these should be taken up with your window installer direct since your contract will be with them.

Yes. If Pilkington energiKare™ energy efficient glazing is installed in any frame type it should comply with Building Regulations for energy efficiency (Part L in England, Wales and Republic of Ireland, Part F in Northern Ireland and Section 6 in Scotland) since it helps to meet the requirement of a minimum Window Energy Rating band C or maximum U-value 1.6.

Yes. The performance may differ for the various types and designs of frame as well as frame materials. The minimum performance requirement for Building Regulations is that the complete window achieves a Window Energy Rating of a minimum of band C or maximum U-value 1.6. However band A can be achieved in all frame types using Pilkington energiKare™ containing one of the products from the Pilkington K Glass™ range depending on type and lower U-values can be achieved by using more highly performing low-e combinations such as Pilkington energiKare™ Advantage.

It is the same as other double glazed units according to the guarantee offered by your window installer.

No, this is not appropriate. Tinted glass is designed to reduce the amount of heat from the sun which comes in and stop overheating of areas such as conservatories. Pilkington energiKare™ is specifically designed for windows and or North facing areas of homes which would benefit from more heat from the sun coming in.

Pilkington energiKare™ is available only in our own glazing or from other companies who have entered into a partner agreement with us. This agreement means that they make and supply according to the specified design which meets the latest European Standards.

Over the typical lifetime of windows it is possible to save up to thousands of pounds as well as reduce the CO2 emissions by millions of tons.

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