Window extensions

Part Two- A-Z Of Roof Windows

velux roof windows

The roof window industry is thriving. With so many people being priced out of moving home, many are opting to improve their current lot with a home extension or conversion. 

Pitched roof windows and flat rooflights are playing an essential role in this growth in popularity thanks to their ability to transform areas of the home into bright, fresh and healthy living spaces. 

Here is Part 2 of the Sterlingbuild A-Z of Roof Windows to give you a more complete picture of the wider roof window industry.

N is for...Noise Reduction

velux soundproof windows

Certain roof windows are built with thicker glazing to prevent unwanted outside noise from entering the home so to improve overall quality of everyday living by making the simple pleasures, such as reading a book, more pleasurable.  

Noise reduction windows carry a sound reduction rating measured in decibels. A window with a db rating of 40 will reduce an outside noise of 80 decibels, such as a loud radio, by half.

Noise reduction windows are made by RoofLITE, VELUX and FAKRO. Read our Make a Sound Investment’ blog for more information.

Shop Noise Reduction Windows

O is for...Options

Picking the right roof window for your loft conversion or home extension can be tricky given the number of possibilities out there on colour, size, material, design and glazing.

However, having this multitude of options should never be considered a bad thing. Having such a diverse range of roof windows just makes finding your perfect window likelier. 

Whether that dream window be a cheap roof window that lets in an abundance of natural light, an electric roof window for the ultimate in convenience or an imperious roof lantern that provides glorious views of the stars at night, the options are there, but the choice is all yours.  

P is for...Planning Permission

planning permission roof windows

As stated on the Planning Portal, you do not normally need to apply for planning permission to re-roof your house or to insert roof lights or skylights as the permitted development rules allow for roof alterations subject to the following limits and conditions.

•    Any alteration to project no more than 150 millimetres from the existing roof plane. 
•    No alteration to be higher than the highest part of the roof. 
•    Side facing windows to be obscure-glazed; any opening to be 1.7m above the floor.


Approval under the Building Regulations will generally be needed for the installation of a new rooflight for the following reasons:

•    To install a rooflight, the roof structure will generally need to be altered to create the opening.
•    The roof will have to be able to carry the load (weight) of the new rooflight. If the roof can not do this then it will need to be strengthened.
•    Any rooflight that is installed will need to prove that it has sufficient insulation against heat loss i.e. is energy efficient.
•    If the rooflight is in close proximity to a boundary, the fire performance of the rooflight will need to be considered.

Do I Need Planning Permission to Install Roof Windows?

Q is for...Quadruple Glazing

Though double and tripled glazed windows make up the majority of the roof window market and will likely always be the more popular glazing options, for those looking to make their home ultra energy efficient, quadruple glazing will do the trick.

Quadruple glazed windows are suitable for Passivhaus building requirements, where the purpose is to make homes as less demanding on unsustainable sources as possible. Unsurprisingly, quadruple glazed windows and rooflight carry extraordinarily low U-values, as seen on the top hung roof windows and flat glass rooflights from FAKRO.

Quadruple glazed windows are not number one when it comes to energy efficiency though. That honour goes instead to quintuple glazed solar roof windows from VELUX which have a U-value of 0.51 W/m²K.

Tell Me More About Energy Efficient Windows

R is for...Rooflights

fakro flat roof window

Though many people refer to pitched roof windows as 'rooflights', here at Sterlingbuild we consider rooflights to be windows made for flat roofs only. 

Rooflights are a natural and cost effective way of introducing more natural daylight into a new or existing flat roofed extension and a means of creating a healthy connection between home and outdoors.

Rooflights can take several forms, for example flat glass window, roof lantern or polycarbonate dome. Some will able to open and provide regular access to the roof, while others will be non-opening.

Flat Roof Window Buying Guide 

S is for...Sterlingbuild

S is also for solar power, sun tunnels and skylights, all lighting solutions that can be found under the roof of Sterlingbuild, the UK’s largest independent seller of roof windows and rooflights.

Sterlingbuild has thousands of flat and pitched roof windows available from world leading brands like VELUX and FAKRO, along with industry upstarts  ECO+ and REAL. Hundreds of our windows can be purchased with free next day delivery.

Should you find your ideal roof window at Sterlingbuild, we give you the option to pay for your product/s on finance through flexible instalments over a period of time.

Finance At Sterlingbuild About Sterlingbuild

T is for... Thermal Efficiency

thermal efficiency in roof windows

Buying double or triple glazed roof windows with argon gas sandwiched between the panes is a great way to insulate your home without having to regularly crank up the heating during the winter.

Thermally efficient windows will reduce heat transfer and keep the warmth of the sun trapped inside the home. When the weather takes a turn for the better, you can simply open your window or air vent to cool down your surroundings.

The thermal performance of a roof window or rooflight can be measured by looking at its U-value. The general rule is, the more glazing- the lower, and therefore better, the U-value- although other factors can bring this value up or down.

U-values explained

U is for...Upstand

A window upstand acts as an interface between the window and the roof it is being installed on. All flat roof windows require an upstand, or external kerb as they’re also known, to be installed for the window to sit on. This upstand must rise up 150mm above the finished roof level at a slight incline to allow effective runoff of rainwater.

External kerbs are normally required to be sourced and built by the customer, traditionally done with excess timber. For instructions on how a rooflight and upstand work together and more on upstand regulations, visit our 'How to Measure Rooflights' page.

Some brands supply upstands along with their windows for a quicker and cheaper installation. ECO+ is one example of this with, as all ECO rooflights come with a PVC upstand as standard.

Shop ECO+ Rooflights

V is for...VELUX


Originators and undisputed leaders in the roof window industry for over 70 years, VELUX are so synonymous with roof windows that when seeing a window installed in a roof, many people will call it 'a VELUX', when in fact it could be a roof window from one of a hundred different manufacturers.

VELUX use only the best and latest technology in all of its products, such as its INTEGRA electric window range and new VELUX ACTIVE smart system that’s lets your windows automatically look after the indoor climate in your home, which you can control and monitor from your smartphone.

When planning and designing home improvements, many people will straightaway turn to this famous Danish brand and make their extension a VELUX Extension. Sterlingbuild is VELUX’s principle UK stockist, with more VELUX windows for sale at Sterlingbuild than any other independent retailer.

Discover VELUX Find Out More About VELUX ACTIVE 

W is for...Walk-On Rooflights

Walk-On rooflights are a highly practical way of bringing sunlight into lower level rooms of the home that would otherwise require costly and constant artificial lighting, for example basements and cellars.

Installed either internally or externally, walk-on rooflights with non-slip glass can be walked on without sustaining any damage whatsoever, making them suitable for roof terraces with frequent footfall.

Creative and attractive walk-on rooflights from Signature are of one Sterlingbuild’s made to measure products,with customisable options available on colour, construction, glazing and more.

Shop Signature Walk-On Rooflights  Shop FAKRO Walk-On Rooflights

X is for...Xenon

xenon gas in roof windows

Xenon gas is an inert gas that is inserted between window panes to improve thermal performance. Gas-filled units will help create a more comfortable indoor temperature than air-filled units, although naturally, they will be more expensive too. This extra outgoing can be made up easily in the long run as a result of the guaranteed savings gas-filled windows will help you make on utility bills. 

Krypton and argon are two other common gases used in roof windows and rooflights, with argon by far the most popular and cheapest option.

Home Improvements- Energy Efficiency

Y is for...You

We can try and convince you to buy a certain pitched roof window or flat rooflight through product descriptions and blogs til the cows come home, but the final decision will always rest with you, a decision that will be dependant on a number of factors unique to you and your home.

So, to save you hours and hours of searching through hundreds of different products with different features and spec, we have created a simple to use window shopping tool that can help you find a suitable window for your needs in under 60 seconds. 

Try Window Shopping With Sterlingbuild

Z is for...Z-Wave

z-wave electric windows from FAKRO

Z-Wave is FAKRO’s smart communications system that it uses on its electric roof windows and which operates through low power radio waves.

Z-Wave windows from FAKRO can be opened and closed with a remote control from any room in the house, a feature that gives you the luxury of placing your windows however high up in the roof you like.

Easily connected to a home’s mains supply, Z-Wave windows come equipped with a rain sensor that can direct your windows to close at the first sign of a downpour. 

Shop FAKRO Z-Wave Windows Discover the Benefits of Going Electric

Read Part 1 of our Roof Window A-Z