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What is Energy Efficient Glazing? EXPANDED

May 2021

Here we discuss in detail exactly how double glazing works, the ins and outs of their energy ratings and how improving your windows will help you save money and reduce sound pollution.

What is double glazing?


Double-glazing is a window consisting of 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, thus keeping warm air trapped inside your home and helping improve energy efficiency.

This extra pane of glass also acts as a secondary barrier to noise, helping keep your home nice and quiet, and strengthens the window to improve security.

Does double glazing keep out noise?

Yes, it does! While it won’t completely block out all noise, installing double glazing can significantly reduce the noise you hear from outside. The amount of noise the windows blocks out can depend on factors including vent size, the age of the windows, etc.

Does double glazing reduce your utility bills and energy usage?

If you’re replacing older units you can be pretty confident it will save energy and therefore money on your bills. Did you know that our homes account for a quarter of all CO2 emissions in the UK and windows can account for up to 30% of the total heat lost from a house? ‘A’ Rated windows can have a zero energy loss over a year cycle or even add energy back into the room via solar gain. As an example, a detached house with 23.7m² of windows and electric heating upgrading from single glazed wooden windows to A-rated casement windows could save £325.26 a year.

What do the window energy ratings mean?

When buying new windows, one of the most important things to look out for is the Windows Energy Rating (WER). They work in a similar way to the energy ratings on electrical goods.

The ratings go from A (very efficient) to G (incredibly inefficient). To comply with building regulations, all windows have to be at least C-rated.

The Windows Energy Rating is calculated using various values:

  • Thermal Transmittance (U value)
  • Solar factor (G value)
  • Air Leakage (L value)

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 – how much energy gained through your windows from the Sun (solar factor). This is measured in kilowatt hours per metre, per year.

L-value – Air leakage through the window. We’re looking for as low as possible here and is measured in kilowatt hours per metre, per year.

We pride ourselves on only providing the best products, with an official  WER ‘A’ Rating on all of our window products.

Kommerling WER +8


It’s a simple fact that windows play an integral part in any home. They provide the obvious functions of allowing natural light in as well as ventilation, but are vital in other areas, like providing escape routes in the event of emergency and enhancing the thermal efficiency of your home. The look and style of your windows goes hand in hand with the functionality, enhancing the overall design and aesthetic of your home, with different styles and colours bringing their own personality.

It’s fair to say that your windows and your choice when thinking about new windows, play a MAJOR role in improving your home.

If you have decided the time has come to replace your old windows, then having a little help before buying will go a long way to making the process as stress free as possible and also a successful experience.

Knowing the right questions to ask is not only important but essential for your bank account. Buying from the wrong company can be a very costly mistake and one we want to help you avoid.

Key Qualities to look for in a Double Glazing Installer

  • Established (trading for over 10 years)
  • Reputable
  • Offers a personal service
  • Professional
  • Demonstrates quality workmanship

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 graded, as this lets you know how much acoustic insulation and thermal efficiency you will obtain from the new windows. The grading is set out by the BFRC (British Fenestration Ratings Council) and is graded alphabetically G is the lowest rating and A is the highest.

Kommerling WER +8.png


Your home is in safe hands when you choose High Performance ‘A’ Rated windows from Bryant & Cairns. Not only will you benefit from real savings on your fuel bills, but you will also be helping reduce the impact on the World’s natural resources.

What accreditation do you have?
This allows you to assess the reputation of the installer. Installers must meet certain standards set by the organisations to be awarded any accreditation.


  • BS7412 PVCu Plastic Windows (CEN3269WDS)  
  • PAS23-1/PAS24-1 Door Security (KM85377)
  • BS7412/PAS24 Enhanced Window Security (CEN3269WDG)
  • Profiles extruded to BS EN12608 specs

What warranties do you offer?

A good double glazing company will offer a 10 year guarantee on the products they supply. So if you are in the unfortunate position of having an issue you will be covered under the warranty and the company will resolve the issue for you at no extra cost. Check to see what is excluded in these guarantees.

For more details relating to Bryant and Cairns Accreditations and Guarantee, visit our 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 thriving company)

Can you supply testimonials?
It’s just as important to check testimonials as this achieves a few things; 1 it shows if the standard of work has been consistently good and 2 shows the company has been established over a long period of time. Bryant and Cairns Testimonials can be read throughout our main website www.bryantandcairns.co.uk

How long have you been established?
A double glazing company that has been in business for over 10 years clearly shows that it has good business practice, has made its mark in the industry and therefore demonstrates it has good workmanship, reputation and provides a good service. Bryant and Cairns are excited to have just entered our 20th Year as suppliers and fitters of windows, doors, conservatories, extensionsorangeries, verandahs, garage conversions and refurbishments throughout the Lothians, Edinburgh and Fife.

How do you invoice for the work?
Avoid at all costs a company that wants to be paid up front or demands a large deposit. A reputable, professional company will not demand such payment terms. Ensure that all payment agreements are included in your contract.

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


What is exactly included in the quote?
When looking over the quotations check to see what is exactly is included and what the extras may be.

Top Tip – Always make sure the quality of the product is like for like so for example the energy rating of the window is the same. This then gives a fair comparison. Don’t compromise on good quality and service for the sake of saving a few pounds.
At the same time make sure that timescales are also documented so you can plan around the small but necessary disruption when the company is on site.

How do you dispose of the old frames?
Nowadays the majority of old upvc window frames can be recycled so to help conserve the environment it is a wise choice to go with a company that recycles the old frames in order to keep the home improvement industry more sustainable.





With delicate styling and uncompromised performance, the Bryant & Cairns Casement window is by far the most popular style of window in our range as it lends itself to virtually any application.


The versatility of the casement window means that you can choose the position of the opening sashes to best suit your needs. Opening sashes are available in top hung and side hung format and are all fitted with high security friction hinges and multi point locking, meeting and surpassing the requirements of PAS24 enhanced security for windows. Special Egress hinges can be fitted for easy cleaning and fire escape situations. With classic styling, the casement system not only has looks that will last, you can also enjoy the major benefits of heat and sound insulation. Our well insulated frames, quality warm edge double glazing units, weather tight seals and multi – chambered profile 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 ingenious design proves an excellent solution where cleaning the outside pane is required from within the room. It is also suitable as a means of escape in the event of a fire and so it is ideal in upstairs locations.

BC_TILT_SHOWROOMSpecifically engineered, the advanced gearing with up to eight locking points around the perimeter of the Tilt & Turn window ensures highly effective security and superb weather performance. The 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. For added safety, a special restrictor is fitted to eliminate the risk of the window being fully opened accidentally. Tilt and Turn windows are at home in both traditional and modern properties alike. With the facility to add a false transom bar to recreate the style of Sash & Case windows, they provide a sympathetic 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


Our Fully Reversible Window is ideal for restricted access locations, where cleaning and fire escape facilities are paramount.

BC_REVERSIBLE_SHOWROOM.jpgIntelligent design means that when the reversible window is being rotated, it protrudes to the outside allowing interior decorations such as blinds, ornaments and curtains to remain unaffected. Operation of the window is simple, with the turn of the handle and a gentle push, the window glides smoothly on it’s special hinges, rotating through 180 degrees into the reverse position, making cleaning a breeze.

Of course the window has built in, lockable safety catches to 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 an old house, especially in areas with conservation rulings in place, but are also gaining new popularity throughout. They are a versatile option that provides excellent ventilation and light and 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 


An important fact to remember when thinking about styles and colours of windows, is the sheer versatility when it comes to PVCu windows.

At Bryant and Cairns we can cater for almost any need, shape or size and 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 either be filled in online and emailed to our team at sales@bryantandcairns.co.uk or why not 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


Screen Shot 2018-05-30 at 13.00.32


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

Categories: Windows, All

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