What is Energy Efficient Double Glazing? Windows Energy Rating | Minimise Noise & Utility Bills

7th May 2019

In this article, discuss in detail exactly how double glazing works. We cover window energy ratings and how replacement windows help you save money and reduce sound pollution.

How is double glazing made?


Double-glazing is a window created from two panes of glass separated by a layer of trapped argon gas. The layer of argon gas has 67% of thermal conductivity of air, making it a poor conductor of heat. Warm air is then trapped inside your home, improving energy efficiency.

The second pane of glass acts as a barrier to noise. This helps to make your home nice and quiet. It also adds strength the window to improve security.

Can double glazing help minimise noise?

Yes! Although it can't completely block out noise, double glazing will reduce sounds from outside. The amount of sound a window blocks out will depend on a variety of factors. These include details like vent size and a windows age.

Can the right double glazing minimise energy use and utility bills ?

You can be confident it will save on both energy use and money on your bills. Our homes account for a quarter of all CO2 emissions in the UK. Old windows account for up to 30% of the total heat lost from a house. ‘A’ Rated windows add energy back into the room via solar gain. If well installed, they can have a zero energy loss over a full year cycle.

Let's look at a detached house with 23.7m² with electric heating as an example. Upgrading from single glazed wooden windows, to A-rated casement windows could save £325.26 a year.

What is WER or a Windows Energy Rating?

When buying new windows, one of the most important things to look at is the Windows Energy Rating (WER). This works in the same way as energy ratings on electrical goods.

Ratings range from A (very efficient) down to G (very inefficient). To adhere to Scottish building regulations, all windows must be at least C-rated.

To calculate the Windows Energy Rating, the following values are used:

U-value – How much heat can escape through the glass (thermal transmittance). Measured in Kilowatt-hours, per square meter, per year.

For example: 2.5kWh/m2.K

This means that 2.5 kilowatts of energy is lost through every square metre of the window every year. That’s every square metre of window boiling the kettle!

G-value – Shows how much energy gained through your windows from the Sun (solar factor). Measured in kilowatt hours per metre, per year.

L-value – Shows air leakage through the window. We’re looking for as low as possible here. Calculated in kilowatt hours per metre, per year.

Bryant and Cairns pride ourselves on only providing the best products. We ensure all windows have an official WER ‘A’ Rating.

Kommerling WER +8


Windows play an important part in any home. They provide the obvious functions of allowing natural light in as well as ventilation. They are also vital in other areas. They provide escape routes in the event of emergency and increase the thermal efficiency of your home. The look and style of your windows goes hand in hand with the functionality. They enhance the design and aesthetic of your home. The different styles and colours available, allow you to add your own personality.
It’s fair to say that your windows and choosing new windows, play a MAJOR role in improving your home.
If you think it's time has come to replace your old windows, then having a little help before buying is a must. It will go a long way to making the process as stress free as possible.
So knowing the right questions to ask is not only important but essential for you and your bank account. Buying from the wrong company can be a very costly mistake and one we want to help you avoid.

Main factors to consider when researching Double Glazing Installers

Here are some key questions that you should ask your double glazing installer.

Are your windows energy rated?

It is important to know what rating the supplier’s windows are. This determines how much acoustic insulation and thermal efficiency you will get. The grading is set out by the BFRC (British Fenestration Ratings Council). WER is graded from A toG, G being the lowest rating and A the best.

Kommerling WER +8.png

Bryant and Cairns only supply High Performance ‘A’ Rated windows. This means you can enjoy real savings on your fuel bills. The energy benefits and long life of double glazing also help to reduce the impact on the world’s natural resources.

What accreditation do you have?

Accreditations allow you to assess the reputation of the installer. Installers must meet certain standards set by the awarding organisations.


What warranties do you offer?

A good double glazing company will offer a suitable guarantee on the products. This ensures your new windows and doors will be covered if any problems arise. The company will resolve the issue for you at no extra cost. Also remember to check to see what is excluded in these guarantees.
For our full Accreditations and Guarantee, visit Bryant and Cairns main site here

Request the company’s full details.

You will want to see proof of the companies;

Full postal address

Land line number

Company number

Show room address (not essential but a sign of an established and thriving company)

Can you supply testimonials?

Reviewing testimonials achieves a few things, 1 it shows if the standard of work has been consistently good, 2 shows the company has been well established over a long period of time.
Read testimonials throughout our main website and google reviews. www.bryantandcairns.co.uk

How long have the double glazing company been established?

If the company has been in business for over ten years, it can often be a good sign. It shows that it has good business practice and has made its mark in the industry. It should signify it has good workmanship, reputation and provides a good service.

How do you invoice for the work?

Avoid any company that wants to be paid up front at all costs, or demands a large deposit. A reputable, professional company will not demand such payment terms. Ensure that payment agreements are clearly shown in your contract.

Bryant and Cairns will not request a penny until the installation has been completed.


What's included in the quote?

When obtaining quotes, be clear on what you are getting. Always check to see what is being sold and what the extras may be.

Top Tip – Always make sure the quality of the product is like for like. For example the energy rating of the window is the same in all quotes. This then gives a fair comparison. Don’t compromise on good quality and service for the sake of saving a few pounds.

Another important point is to make sure that timescales are also documented. This will allow you to plan around the small but necessary disruption when the company is on site.

How do you dispose of the old window frames?

These days, the majority of old upvc window frames should be recycled. To help conserve the environment, it is a wise choice to go with a company that recycles the old frames. Actions like this help keep the home improvement industry more sustainable.





Our Casement window is by far the most popular style of window in our range. This is due to the flexibility of design and stunning finishes available. The casement window lends itself to almost any application.


The versatility of the casement window means that you can choose the locations of the opening sashes. Your choices include top hung and side hung formats. All openers have high security friction hinges and multi point locking. All components meet and surpass the guidance for PAS24 enhanced security for windows. We can also fit Special Egress hinges for easy cleaning and fire escape situations. Our casement window system not only looks great, it also provides the major benefits of heat and sound insulation. Insulated frames, weather tight seals and multi – chambered profile all ensure that heat loss is kept to an absolute minimum.


‘A’ Energy Rated as standard
Distinctive Sculptured shape – Looks like real timber
Designer handles in a range of colours
Low sightline gaskets
Multi-point stainless steel twin claw locks
NEW Prestige range of colours now available

For more information on casement windows and colours, visit our main site here


This clever design provides an ingenious solution, meaning the outside pane can be cleaned from within the room. It is also suitable for escape in the event of a fire and so it is ideal in upstairs locations.


The advanced gearing has up to 12 locking points around the perimeter of the Tilt & Turn window. This ensures highly effective security and superb weather performance. The unique hinge and locking system enables the window to operate in two modes. A simple 45 degree rotation of the handle tilts the window into the ventilation position. A further 45 degree rotation allows the window to turn in for easy cleaning. A special restrictor eliminates the risk of the window being fully openened. Tilt and Turn windows are suit both traditional and modern properties alike. Adding a false transom bar can recreate the style of Sash & Case windows. This creates a perfect solution to flatted dwellings in many conservation areas.


‘A’ Energy Rated as standard
Tilt for lockable ventilation
Designer handles in a range of colours
Fire Escape functionality
Up to 8 locking points
NEW Prestige range of colours now available

For more information on tilt & turn windows and colours, visit our main site here


Fully Reversible Window are ideal for restricted access locations. These include areas where fire escape and access for cleaning are needed.


When rotated, the reversible window protrudes to the outside. This intelligent design means objects such as blinds and ornaments remain unaffected. Operation of the window is simple. With the turn of the handle and a light push, the window glides on it’s special hinges. Rotating the window through 180 degrees into the reverse position makes cleaning easy.
The window has built in, lockable safety catches. The catches eliminate the possibility of young children operating the window.


‘A’ Energy Rated as standard
Easy Clean Facility
Designer handles in a range of colours
Multi-point locking
Advanced hinge mechanism
NEW Prestige range of colours now available

For more information on reversible windows and colours, visit our main site here


Sash and case windows are often used when renovating older buildings. They conform well in areas with conservation rulings in place, but are also gaining new popularity throughout. This versatile option provides both excellent ventilation and light. It can bring a sense of grandeur to a new build or terraced house.
For more information on sash & case windows and colours, visit our main site here


The wide range of styles and colours make PVCu windows an incredibly versatile choice.

At Bryant and Cairns we can cater for almost any need. We are always aiming to make it easier for you to decide. Why not download our easy to use style chart and enquiry form. It can be completed online and emailed to our team at sales@bryantandcairns.co.uk

Alternatively, print it out and bring it in to our conservatory village and showroom site in Loanhead near IKEA

Download your free online enquiry sheet here

Please note, if you wish to fill it in online, you may need to download Adobe reader if you do not already have it. This can be downloaded here

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If you would prefer to speak to one of our brilliant advisors, feel free to call us on 0131 440 2855 or visit us:


Mon – Fri 10.00am – 5.00pm Sat – Sun 11.00am – 3.00pm
or by appointment out with hours

2/3 Borthwick View, Pentland Industrial Estate, Loanhead,
Midlothian, EH20 9QH Next to the new IKEA Warehouse

For all other enquiries, you can contact us here