Window extensions

Flat Roof Window Buying Guide

Your Guide to Flat Roof Windows

Choosing the right roof windows for your flat roof extension can enhance your new space no end as the natural light that funnels in from the window opens the room up, creating a fresher and healthier living environment.

Our flat roof window guide will help you decide which type of rooflight is best suited to your needs and will explain everything you need to know regarding glazing, operating methods and energy efficiency.

velux flat roof windows installed in extension

Rooflights for flat roofs

What is the best kind of rooflight for my room? There's a balance between visual appeal and choosing the right material for the job. We're here to help you choose.

Flat glass rooflight


Flat glass rooflights are one of the most popular flat roof windows on the market. An ultra-modern design mixes style with efficiency, meaning you can give your home that wow factor while saving on energy bills and enjoying comfortable levels of insulation. 

Known for their brilliant energy performance, ECO+ have flat glass rooflights that come with built-in LED lights, available in a host of colours to fit any theme.

VELUX’s curved glass rooflight would be a showpiece item in any room, while also lowering maintenance needs with its curved top providing natural drainage.

Available from VELUX, ECO+, REAL, FAKRO, and Signature.

Flat glass domed rooflight


For long a popular choice on both residential and commercial roofs, flat glass domed rooflights are made using at least two layers of glass covered by a single skin dome, formed in a high insulation PVC frame. 

The substantial list of benefits of flat glass domed windows include; reduced maintenance, high energy efficiency and effective sound insulation. FAKRO offers a quadruple-glazed rooflight for additional sound insulation and even greater energy efficiency. 

The window is suitable for installing on roof pitches between 0° and 15° and comes in fixed, manual and electric operating styles.

Available from VELUX, FAKRO and Sterlingbuild.



Contemporary roof lanterns consist of glazing pieces separated by aluminium trims that meet in the middle to form a pitch. The stunning views they offer of the sky above are sure to astound all that look through.

Lantern rooflights have the much-desired effect of making your room appear bigger due to the impression given of a higher ceiling. They come in a number of different pre-set sizes but can also be made bespoke to fit flush with any design. 

Lanterns come in fixed, and manual operating styles and are available in double glazing as standard, with triple glazing alternatives available for added energy efficiency and noise insulation.

Available from Korniche and REAL.

Walk-on rooflights


Manufactured using a one-piece stainless steel design, walk-on rooflights are an extremely popular choice for basement conversions as they are a practical solution to introducing natural light into areas that the sun struggles to reach.

Walk-on rooflights are made to withstand a great deal of weight and feature an enhanced grip and safety coating that prevents slipping in wet conditions.

The rooflights are available in all levels of glazing while the exact dimensions of the window can be made to order so to fit your designs.  

Available from FAKRO and Signature.

Polycarbonate domes


Polycarbonate domes are the most affordable flat roof window option and are ideal for outbuildings and large commercial developments. Despite their cheap price, roof domes offer a number of benefits to your home. 

With an impact strength that is up to 250 times greater than that of glass, polycarbonate is as close to unbreakable as you can get with a roof window.

Good quality polycarbonate domes with a UV-absorbing surface layer should be resistant to discoloration at the same time as maintaining light transmission.

Available in all four thickness levels, in circular or pyramid design.

How would you like your window to operate?

Manual, Electric or Solar. Here is our rundown on all three window operating styles to help you decide.



In rooms where no extra ventilation is needed due to enough coming from other sources such as Bi-fold doors and uPVC windows, having a non-opening/fixed rooflight is a smart option to save a lot of money

Walk-on rooflightslanterns, flat glass rooflights and polycarbonate domes, are available in a non-opening operation style.



Manually controlled flat roof windows are a very good choice for homeowners looking to ventilate their home. Offering the same levels of fresh air flow as electric rooflights, manual roof windows can be opened by hand or with an opening rod.

Lanterns, flat glass rooflights, flat glass domed rooflights and polycarbonate domes are all available in manual.



The most contemporary and flexible way of opening a roof window. Controllable via a wall switch or remote control and operational from anywhere in the home, electric rooflights have become a popular choice for the modern homeowner.

Electric operation is available for flat glass rooflights, flat glass domed rooflights and polycarbonate domes.


The finish of choice for most flat roof windows, clear glazing offers unobstructed views of the sky above. Unlike clear glazing, neutral glazing is not fully clear as the protective coating on the glass produces a slight tint. 

Neutral glazing is available on both Korniche and REAL lanterns, while clear glazing can be applied to most of our flat roof windows.


A sensible choice for bedrooms, bathrooms or anywhere else where your private space is important, obscure glazing is designed to offer complete privacy and achieves this by making it impossible to see in or out of when closed.

Signature are specialists in obscure-glazed rooflights, offering a large range of sizes in fixed, manual and electric operating styles. 


Blue tint

If you are worried about the effect of the sun on your new sofa, subtle blue tint glazing can reduce harsh glare and protect furniture from fading.

The addition of a blue tint can also create a blue sky feel, perfect for fixed windows. REAL has a number of lantern sizes available with blue tint.   

Bronze tint

The main purpose of bronze tint glazing is the same as blue tint- helping to reduce glare from the sun and thus protecting your furniture from fading.

Too much glare can also make pleasurable activities such as reading a book or watching TV harder to enjoy, a problem that bronze tinted lanterns offer the ideal solution to.

Which type of window glazing is best?

Glazing is an important part of any rooflight. Which kind of glazing gives me the best u-values and noise reduction? Here are the options outside of standard double glazing.


Triple glazing

The benefits of glazing are the same for both flat roof windows and pitched roof windows, with the general rule being that the more glazing, the better the insulation. 

The insulation credentials of rooflights can be measured by their u-value, with the lower the rating, the better the window as an insulator. FAKRO triple glazed flat glass rooflights come with a U-value of 0.88 W/m²K.



Quadruple glazing

Everything triple glazing offers but magnified. A fourth layer of glass makes quadruple-glazed flat roof windows one of the most energy efficient rooflights on the market.  

FAKRO lead the way in quadruple glazing, with their wide array of rooflights perfect for passive buildings and energy efficient constructions. Quadruple glazing can offer U-values as low as 0.58W/m²K.


Some other products you might want to consider purchasing to complete the look and functionality of your rooflight.


Flat roof blinds

Blinds and shutters are the perfect way of controlling how much light enters the room. As well as this, they are an important part of your room's decor, adding a touch of colour and style to fit whatever theme or ambience you might be looking to create. 

We have a huge selection of blind styles and sizes for sale, for inside and outside of the window. Pleated, energy pleated, blackout and awning are just some of the flat roof blind designs we feature in our comprehensive Blinds Buying Guide.


Operating accessories

It is important to consider what accessories you might need to pick up along with your flat roof window. Some, such as an opening rod, can be essential if your manual flat roof window has been installed out of arm's reach. 

If you really like the look of a certain FAKRO pitched roof window but you need a window for a flat roof, installing pitched on flat is no longer a problem with FAKRO’s roof kerbs and EFR flat roof gable system.