The War Of The WER’s?

Over the last four years there have been many articles written about Window Energy Ratings. Some singing the praises of the new simplified system, with which consumers and specifiers can easily compare competing products. They talk about how using a simple and easy to understand ranking and labelling system makes buying new windows far less daunting for the average homeowner. They also talk about how energy efficient windows will save you money on your household bills and can even put heat back into your home by means of solar gain.

On the flip side other parties have written about the failings and limitations of the Window Energy Ratings and believe that these new ratings are simply made up rubbish aimed at trapping the general public into believing that one window is vastly superior to any another just because of its energy rating. They state that Window Energy Ratings provide no true measurement for energy performance, and urging people not to be duped by the British Fenestration Rating Council, and their WER Scheme. They call the WER system just another double glazing sales trick and a way to increase competition and profit margin within the glass fabrication industry. One blog even referred to WER’s as ‘The Emperors New Cloths’.

Many people are concerned that the potential energy savings, and reduction in CO2 emissions may not be fully realised due to the ambiguous nature of these WER calculations, but many also believe that overall they are a step in the right direct and stop so called ‘cowboy double glazing’ firms from specifying outdated products with compliant double glazed sealed units. 

The facts about Window Energy Ratings

In October 2010 the WER rating scheme was introduced as a new method by, which windows could comply with the Building Regulations. It was made mandatory for all companies within the window industry to test and rate their products, if they wanted to be a part of it. Since it was in many cases easier to achieve the minimum WER ‘C’ than the minimum U value of 1.6, now required by the Building Regulations, many companies did exactly this. The ratings are much the same as white goods, used to prove the energy efficiency of a product. Windows are rated A to G, and contrary to popular opinion a D - G rated window could still comply to the building regulations so long as it had a U value of 1.6 w/m²k or lower. Window Energy Ratings are an alternative method of compliancy, to the humble U value, but how can a window be energy efficient if it doesn’t consume energy in the form of gas or electricity? Its all very confusing isn’t it.

Even now years later many people still do not understand Window Energy Ratings, what they are and confuse them with thermal efficiency (U values) and even believe that they provide a measure of manufacture quality or security. Some people even talk about A rated glass, which is simply a term used in the industry to describe a sealed unit with a certain specification. This specification will in most cases (but not all cases) result in an overall Window Energy Rating of ‘A’, so it kind of makes sense. But glass cannot itself have a Window Energy Rating and this sort of terminology or industry slag, muddies the water and further increases ignorance and confusion.

But what purpose do Window Energy Ratings serve, if any? What are they, and how are they calculated?

If you are confused about Window Energy Ratings, We Can Help?

We have devoted an entire section of our website, in an attempt to clarify and answer exactly this. If you wish to get to the bottom of the Window Energy Rating scheme then it’s a very good and unbiased view to Window Energy Ratings. It will provide you with just the facts; without any speculation into Government Agenda and the glass fabrication industry. Nor does it try to use WER’s as a tool to try and sell you new energy efficient windows. We believe that it is certainly worth reading before you decide to buy yourself some new windows.

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What is 'A Rated' Glass?

Whether you are a domestic customer or trade customer you may have heard the term 'A Rated Glass' being used. There is however no such thing.

This term is becoming frequently used in the uPVC industry to describe a glass specification that will allow a window to achieve an 'A' rating. The actual glass specification they are referring to is:-

4mm Clear Float - 20mm Argon Gas Filled Spacer (90%) with Swiss V (or similar) Thermal Spacer Bar - 4mm Low-e (softcoat). This glass make-up achieves a centre pane U-value of 1.2 W/m2K.

In the majority of uPVC window systems this glass allows the window to achieve an Window Energy Rating of A, hence why it is being increasingly referred to as 'A Rated Glass'. Unfortunately, it does not always result in an overall A rating when Glazed into window systems and it is becoming more and more confusing for the end customer and trade alike.

The Window Energy Rating (WER) system applies only to windows, it also only applies to the window as a whole. Individual components cannot themselves have a window energy rating, i.e. the glass or frames.

This so called 'A Rated' glass specification we use as standard for the majority of our products. Using this so called ‘A’ Rated glass in one of our aluminium Smarts 47 windows (for example), achieves an overall 'C' Rating. Although this is still fully compliant with current building regulations, it may not be what the customer is expecting.

Find out more about WER’s here: http://www.duration.co.uk/Window-Energy-Ratings.asp

Lower Your Energy Bills By Specifying Planitherm SGG

Saint-Gobain’s Planitherm glass is proven to be one of the most energy efficient glasses available in the UK.  Planitherm is a new generation energy saving window glass that uses an advanced ‘softcoat’ coating that helps to retain more of the internal warmth whilst capturing free energy from natural daylight (known as passive solar heat gain). This equates to lower energy bills compared to windows with standard glass. By specifying Planitherm in your windows you can cut your energy bills by as much as 28%*. All glass has a slight tint, however Planitherm products are almost completely clear and maximise the amount of natural light coming in.

Saint-Gobain is the largest supplier of high performance low-emissivity (or low-e) glass’s in Europe, and is one of Pilkington’s largest competitors here in the UK. Planitherm glass is not a new product; it has been available and manufactured in the UK since 2004. Duration Windows have been supplying Planitherm Total+ for many years. However since 2010 when Window Energy Ratings (WER’s) became part of the revised more stringent part L of the Building regulations, we have been supplying Planitherm glass as our standard double glazed sealed unit for the majority of our aluminium windows and doors.

This glass is designed specifically to to keep interiors more comfortable in the winter months and improve your home's energy efficiency. It is far easier to achieve a Window Energy Rating (WER) of ‘A’ when using Planitherm Glass, as it provides high solar gain, capturing free energy from natural daylight. Window Energy Ratings provide an outline or overall value for how energy efficient a window is and are an alternative to thermal efficiency (U-values) for compliance to the building regulations. WER’s are calculated by offsetting the heat loss through a window against the solar gain through the glass. Window energy ratings were introduced to the building regulations to try and help to reduce CO₂ emissions and protect the environment. The ratings range from A to G with a C-rating being the minimum rating required for compliance with current Building Regulations (Alternatively an overall U-value of 1.6 is required).
Find Out More About Window Energy Ratings.

The Planitherm range can be combined with many Saint-Gobain Glass products, providing a multitude of high performance of high performance, multi-functional glazing options, inculding:

• Self-cleaning and/or solar control glazing
• Acoustic insulation
• Safety and security
•  Obscured and/or decorative glazing

Planitherm products are the ideal low-e solution. Not only do SGG Planitherm products allow free heat and light from the sun to pass through the glass and warm your home, but they have a transparent metallic coating that reflects heat from radiators or fires back into the room, rather than allowing it to escape through the windows. This further contributes to the energy efficiency of your windows. The thermal insulation provided by low-E double glazing is three times more efficient than that of standard hard coat double glazing, such as Pilkington’s K glass. The coating is permanent and hermetically sealed within the glass unit so will last the lifetime of the window. Of course all old, uncoated, double glazing offers a limited level of heat retention. However, Building Regulations now state that an energy efficient window glass must be used in all replacement windows. A double glazed unit containing Planitherm is on average 40% more thermally efficient than standard non-coated double glazing.

Reasons why we use Planitherm Glass products:

• Free Solar Gain - Planitherm uses advanced coating technology to capture free energy from natural daylight, helping to heat your property.
• Thermal Insulation - The advanced coating reflects heat back into the room, meaning less energy is needed to heat the home to the desired temperature.
• Optimal Window Energy Rating - Planitherm combines with virtually any window frame to achieve a Window Energy Rating (WER) of C and an A rating is easier to achieve allowing for easy compliance to the Building Regulations.
• Haze & Tint Free Windows - Planitherm maximises the amount of natural light into the home, without the haze or tint effects associated with older double glazed windows.
• Eliminate Condensation - Planitherm helps to virtually eliminate internal condensation, reducing draughts and cold spots in and around the windows. 

For more information on the glass we use as standard, the glass we offer as upgrades and glass specification please visit our website at www.duration.co.uk

*Savings calculated using the GGF energy savings calculator based on upgrading from single glazing to A-rated double-glazed windows in an average gas heated detached house.

Glass... What are my options??

We at Duration Windows found this interesting artical in the July addition of Build It Magazine and thought you might be interested in its content.

From energy-saving coatings to self-cleaning panes, there’s plenty to choose from when specifying your home’s glazing, says Chris Bates.

Glazing has come on leaps and bounds in recent years. There’s a product out there to suit almost any application. But with so much choice available, how can you go about specifying the right product? In some cases, the decision is simple – safety glass is an essential for stair balustrades, for example. In others, you’ll need to weigh up which option is best suited to the lifestyle you want your new home to deliver.  

Comfort & efficiency 

For most homeowners, saving energy and keeping running cost down is the basic starting point when specifying glazing. The importance of energy efficiency is reflected in Building Regs, too, which require a minimum ‘C’ window energy rating (WER) for all new units.

All efficient glazing is referred to as ‘low emissivity’ (Low-E), but there are subtle differences between products. Some feature a ‘soft’ thermal coating that favours heat retention and offers low U-values. These include Pilkington’s Optitherm and Saint Gobain’s Planitherm. Others feature a ‘hard’ coating that, while still providing good heat retention, puts more emphasis on solar gain (g-values). Pilkington’s K glass falls into this category. In our mild climate, there’s relatively little to choose between soft and hard coats. For that reason, the WER system considers both U-values and g-values, so A to C grades can be achieved with either type of Low-E glass. But there is choice within each category. As well as the standard K Glass, for example, there are two additional types. The S version offers better U-value but poor g-value, while the OW spec matches the standard U-value but gives a clearer glass and a slightly better g-value. On a typical double glazed unit, the inner pane carries the Low-E coating (on the cavity side). The outer pane can either be of clear glass to allow the maximum possible amount of daylight to filter through, or could be treated with a solar control or other type of coating. The gap between the panes is filled with gas (argon is most economical, krypton more efficient) or fitted with warm-edge spacer bar – or both for maximum heat retention.

Minimal maintenance

Washing down windows can be a real chore, especially if your new home features vast swathes of glazing or hard-to-reach features such as skylights. You can take a lot of the effort out of maintenance by specifying self-cleaning glass, such as Saint Gobain’s Bioclean or Pilkington’s Activ. Its external coating uses UV rays from daylight to break down organic dirt and prevent other types adhering to the glass. The coating also causes rainwater to ‘sheet’ down the glass rather than forming droplets, giving the whole pane a natural wash. Self-cleaning glass won’t take all the legwork out of maintenance, but will mean you can wash windows less frequently and should make the job quicker, too.  

Safe and Secure

If you’re keen to provide the best possible protection for your home, laminated security glass could be a wise investment. It’s made up of sheets of glass held together with clear plastic film – in the event of a breakage, the fragments adhere to the film to slow or even prevent entry. Simpler laminated products – perhaps using just one or two films – can also be used as safety glass.

Toughened glass is more commonly specified for applications where safety is paramount (such as for stair or balcony balustrades). It’s heat treated during manufacture to produce a product around five times stronger than normal glass and, in the event that it does break, shatters into tiny fragments with dulled edges.

Noise reduction  

New double glazed units provide a measure of in-built sound insulation via the draught proofing. But if you’re building near a busy road or railway line, or you want to introduce some sound deadening for internal glazed partitions, you can upgrade to acoustic glass. This is a laminated product, with two sheets of glass sandwiching a sound-reducing inter-layer. You can cancel out even more noise by opting for different thicknesses of glass in double-glazed units.  

Light and privacy

Maximise natural light levels internally is, understandably, a major goal for many self builders. The first step is to use glass for the outer pane of your home’s double or triple glazing. For even better views you can switch to extra-clear, low-iron products such as Saint Gobain’s Diamant, Which is suitable for everything from windows and external doors to internal partitions and stair balustrades.  Bear in mind, though, that allowing too much daylight – and its associated UV rays – into your home can lead to overheating in summer. That’s where solar control glass comes in. Pilkington’s Optifloat Tint reduces both heat and light penetration, which can be desirable in certain areas of contemporary glass-filled homes where privacy is important. At the other end of the scale, the company’s Suncool range filters out solar heat while still allowing high levels of natural light pass through.

Hope you found this artical helpful when talking about glass and U-values. Please check out some of the pages below from our website for more useful information:

Glass Options: http://www.duration.co.uk/GlassOptions.asp

Window Energy Ratings: http://www.duration.co.uk/WindowEnergyRatings.asp

Aluminium Windows: http://www.duration.co.uk/AluminiumWindows.asp

Understanding Energy Efficiency

We at Duration understand that energy efficiency ratings can be complicated to understand - so we have put together a guide to help resolve the mystery of energy efficient windows.

It is widely known that a large percentage of the heat from your home is lost through the windows - that is why understanding energy efficiency can come in handy, helping you to save money when heating your home.

The guide explains the ratings and how energy efficient windows work. There is also some useful information on what to look out for when buying energy efficient windows.

Follow the link to see the guide:

http://www.duration.co.uk/brochures/misc/Energy%20Efficient%20Windows%20Guide.pdf