A guide to loft windows: Types and options available for your loft conversion plans

From rooflights to dormers, there are a number of options to consider when selecting your loft windows and your final choice will be determined by factors such as the roof design, orientation of the space, room shape and usage.

But, while talking to your architect about what you want to achieve with your loft conversion will all influence what you purchase and how your loft ultimately looks, other factors such as planning permission, building regulations and structural issues will also play a part in deciding which is the right type of loft window for your extension.

In this guide to loft windows we take a look at the options available so you can understand which will be the best glazing solution for your extension project.

Types of loft windows

When it comes to choosing the right type of loft windows for your loft conversion ideas, although letting enough light in will play a part in your decision making, it's not the main deciding factor, says George Vizor, director of Woodrow Vizor Architects.

“Lofts are typically the brightest part of a home, so we don't tend to worry about them being too dark,” she says. “Instead, we focus more on the views out and internal space planning.

"We also always undertake concept studies to explore options and specifications to find the best solution," she adds. "This could be integrating window frames into fixed joinery for a clean material palette; using sliding doors and windows free from inward swings to allow more flexible furniture layouts, or ensuring opposing windows aid cross ventilation.”

So what are the main options available to you when choosing the best loft windows to use in your overall design?

George Vizor

Dormer windows

In the UK, dormer loft conversions are one of the most popular types of loft conversion meaning dormer windows are subsequently one of the most common types of glazing seen in loft conversions and extensions.

But what makes dormers a popular choice?

“Dormers are designed like a raised box shape that protrudes out of the original roof of the property and are popular as they provide additional headspace, and usable floor space in lofts, which usually have low or sloping ceilings,” explains Rebecca Clayton, communications director at IQ Glass.

In terms of the types of loft windows you can use, this largely depends on the size and style of your dormer. However, casement windows, a popular style of window used in many properties can be suitable and beneficial if you are looking to match the style of your loft windows to the rest of your home.

Rebecca Clayton

Rebecca Clayton is communications director at IQ Glass. She has many years of experience with the company, who specialise in architectural glazing and installs some of the most pioneering architectural glass technology available today. 

Rooflights

Another popular option when extending into your loft is a Velux loft conversion. As well as a type of window commonly referred to using the Velux brand name, the more generic term for this type of loft window is rooflight.

Rooflights are a good solution for when there isn’t space for vertical windows. They follow the slope of the roof and can fill a room with natural light from above, however as they are angled towards the sky, they won’t capture any views.

Manual and electrical roof windows allow for control over the airflow, while some include rain sensors that automatically close in wet weather. In some projects automated smoke ventilation windows may also be specified to fall in line with fire safety regulations.

“Rooflights are most commonly used on the front roof slopes, but can obviously be used anywhere," says Melissa Robinson, director at MW Architects. "However, people tend to avoid fixed flat roof lights at loft level as they can’t be accessed for cleaning. This also means specifying self-cleaning glass is a good tip for loft glazing whether they are openable or not,” she adds.

Another option if you have access to a rooftop garden from your loft conversion is a sliding box access rooflight, suggests Rebecca Clayton, noting how they are perfect for terraced or townhouse-style homes. Operated electronically by the push of a button, they can allow the inhabitants the opportunity to step outside if access permits.

Melissa Robinson

Melissa Robinson is a director and architect MW Architects and has over 14 years experience in the field. With creativity in problem solving and a keen focus on materiality and construction detailing, she ensures realised designs are achieved as intended. Melissa is an active member of the RIBA Small Practice panel advisory group, and is involved in other initiatives such as encouraging young women into architecture.

Gable end windows, picture windows and doors

Other loft window types in larger projects can include gable-end windows, picture windows, full height windows, balcony windows or even sliding or bi-fold doors. And while they all provide vast amounts of light, they also come with some additional considerations.

“Gable-end windows are an impressive installation within loft conversions,” says Rebecca Clayton. “The gable-end (the triangular upper section of the side of a property that has a ridged roof) can provide an impressive influx of natural light while also creating stunning views. In some instances," she adds, it may even be possible to install a loft conversion balcony, giving the feeling of outdoor access."

However, when installing large windows in a loft, “if full height glazing is used then the glass needs to be thicker for building regulations," says Steve Bromberg, managing director of Express Bi-folding Doors, "and if doors are included, then a Juliet loft balcony will be needed as well."

Positioning loft windows

Where you place your windows will largely depend on the type of loft conversion you are adding, as well as your loft layout ideas. Nonetheless, positioning loft windows will require getting the right balance between light, privacy and ensuring you have the maximum amount of space in your loft conversion.

One of the types of loft window that can require extra consideration is rooflights, as while it may be tempting to install numerous rooflights to flood the space with light, a more strategic approach can yield better results.

“The adage "less is more" often rings true and careful placement of fewer, well-positioned rooflights can create a more dramatic and visually striking effect while also mitigating the risk of overheating,” says Sean Ronnie Hill, founder of Rise Design Studio.

And, while it may seem they only provide light and loft ventilation, they can also add head height to a sloping ceiling. “Placed to the side of a bed, in front of a WC or over a shower or bath for example can help you maximise a low headroom space by giving an extra 15-20cm,” says George Vizor. This may not seem like a great deal but it in fact opens up layouts that would not have been possible otherwise.

However, as they are positioned above head height, screening such as built-in blinds is also recommended for rooflights, especially if they are positioned directly over a bed in loft bedroom conversion ideas so that you're not woken by bright, early morning light.

Structural considerations

When specifying your loft windows, the loft structure will need to be assessed to ensure that it is strong enough to support additional glazing and your architect or builder should check the weights with your supplier.

"Pyramid rooflights, for example, are very heavy and need lifting into position," advises Steve Bromberg. "Likewise bonded and frameless skylights will need to be carried into place, so access and safety must be considered.”

“Some of our windows can weigh up to 220kg,” adds Jessica Draper, digital & marketing executive at Fakro, "but they can all be fitted from the inside or outside, depending on what access you have.”

Preventing overheating

Lofts are renowned for overheating and glazing can play a large part in this so it's important to take this into account when deciding on positioning, functionality and the type of glass you specify for your loft windows.

“Too much glazing alongside the thermal upgrading of the roof that naturally happens in loft conversions, can result in these rooms being quite warm,” says Melissa Robinson.

The orientation of your property can also affect this, so where possible it is advisable to install the largest, or main proportion of rooflights to the north facing side of the building in order to achieve light but minimal solar gain.

“All openings being made need to be carefully thought through and integrated into the wider strategy of loft insulation and construction detailing, says George Vizor. “Small changes such as the use of triple glazing or introducing external blinds and solar control glass can dramatically change the thermal comfort of a loft making it far more usable in the summer without having to go down an air conditioning route.”

On the flip side, glass is often where heat escapes, so you want glazing with a good U value to prevent this. “The ability to open the glazing in the loft is important for natural ventilation and airflow. Trickle vents should also be used for the same reason, otherwise moisture will build up in the space," adds Steve Bromberg.

Rules and regulations

“Generally speaking the majority of loft conversions are carried out under householder permitted development rights (PD). This does mean that as long as you are within the permitted development guidelines for size and materiality, the form, and equally the windows, have more design freedom,” says Melissa Robinson.

“Adding glazing to your loft will generally fall under PD as long as you are using similar materials to those in the rest of the existing house. But it is always worth getting a certificate of lawful development from your local council to confirm this so you don't encounter any problems later on,” adds George Vizor.

“Plus any windows or rooflights on the side elevation have to follow stricter guidelines to prevent overlooking your neighbours.”

Building regulations will also have an impact on your glazing choices regarding factors such as safety and fire escapes.

“Setting out clear window sill heights and how windows open is key to complying with building regulations and particularly Part K (Protection from falling)," says George. "Any glazing below 80cm needs to be toughened or protected by a balustrade if openable."

Tips for a smooth loft window installation

“Common mistakes people make when selecting loft glazing include overcrowding the space with too many rooflights, neglecting the importance of ventilation and underestimating the challenges of installation, particularly in terraced properties where access can be limited," says Sean Ronnie Hill. "It's also crucial to consider both U-values and G-values to ensure a comfortable living space year-round”

"Architects tend to want everything as big as possible, but in town houses cranes are required to lift the product into place which will involve shutting down the road," warns Steve Bromberg. "The products may also need servicing, so if there is ever an issue with the product, or it needs replacing, then remember the crane will need to be hired again.

"And finally, don't forget to schedule in your scaffolding," he adds. "If there are works going on at the ground floor the scaffolding needs to be down, so often your overall renovation will need to be phased, with the loft installation taking place first.”

If you're embarking on a loft conversion extension, find out the answer to how long does a loft conversion takes so you can work out the best time to start, and if you're not sure you have sufficient head height, see if raising a roof for a loft conversion could provide you with a solution.