Rooflight dome or roof lantern: what is the difference?

Rooflight dome or roof lantern? A rooflight dome is a small roof opening, usually plastic, in a standard size. A roof lantern is a larger glass roof element with aluminium profiles, made to measure. A dome is cheaper and can often be opened. A roof lantern gives more light, insulates better and simply lets you look up at the sky. Which one fits depends on the room below and what you want from it.

What is a rooflight dome?

A rooflight dome is a domed or flat roof opening on an upstand in a flat roof, usually made of acrylic or polycarbonate. You often see them above bathrooms, hallways, landings and garages. They come in fixed standard sizes, often twin or triple skin, and many models can be opened for ventilation.

There is also a glass rooflight: a flat sheet of insulated glass in a frame. It looks closer to a roof lantern, but is usually limited to smaller sizes.

What is a roof lantern?

A roof lantern is an elongated glass roof element with an aluminium frame that spans a large opening in the roof. It is made to measure and has a pitch or a ridge so that water runs off. DagLichtDesign makes four roof types, all four for a flat roof. To replace a plastic dome, most people choose a mono-pitch roof lantern: an aluminium frame in any RAL colour, with HR++ double glazing as standard.

Rooflight dome or roof lantern: the differences

The biggest difference is insulation. HR++ glazing has a U-value of around 1.1 W/m²K, triple glazing around 0.5. A twin-skin plastic dome generally insulates noticeably less, although there are insulated versions that perform better. With a dome, always look at the U-value of the whole product, including the upstand.

The experience differs too. Through clear glass you see clouds and blue sky, through most plastic domes only diffuse light. Some plastics become duller or yellower over the years due to UV light; glass keeps its clarity.

• Light: clear glass lets in more and more natural light
• Insulation: HR++ or triple glazing insulates better than plastic
• Noise: rain drums less loudly on glass than on plastic
• Size: a dome is standard, a roof lantern is made to measure
• Ventilation: many domes open, with a roof lantern you ventilate via the wall
• Price: a standard plastic dome is clearly cheaper

When is a rooflight dome enough?

A rooflight dome is a good choice for a small space where you mainly want light and ventilation, such as a bathroom, a stairwell, a storeroom or a garage. You do not look up through it, the opening is small and the budget matters more than the view. A dome that opens is also handy in a bathroom for letting out moisture.

When do you choose a roof lantern?

You choose a roof lantern for a room you live in: a living room, a kitchen or an extension with a roof lantern. There you want plenty of daylight, a view of the sky and a glass surface that does not feel cold in winter. For a long, narrow opening, a roof lantern is also more logical than a row of domes.

If you are torn between a roof lantern and a flat roof window, also take a look at roof lantern or roof window on a flat roof.

Replacing a rooflight dome with a roof lantern

Replacing an existing dome with a roof lantern is often possible in the same opening or an enlarged one. If you cut a larger opening, the builder or a structural engineer must assess whether the joists allow it, because you usually interrupt joists. Connecting to EPDM or bitumen is covered in our installation manual. All the steps are in replacing a rooflight dome with a roof lantern.

Frequently asked questions