What is the difference between a roof window, a skylight, and a rooflight?

There are a lot of products that are on the market right now that can offer different degrees of natural daylight and a lot of people are familiar with roof windows, rooflights, and even small scale skylights. We all tend to really enjoy spaces that are well lit, and so the increased use of windows when it comes to the building is always a great way to improve the look of your home. However, what is the difference between these products? Is a rooflight different from a roof window or is a skylight different from a rooflight?

Roof window, skylight or rooflight?

Skylight is a just a term that was originally used by manufacturers for a lot of different products, which range from small, domestic units that were installed on a traditional pitched roof, all the way to larger skylight units that are installed on terraces or flat roofs. This is just a generic term that can cause issues and even confusion for customers as this product can differ a lot when it comes to application scale and function. There are some cases where the term skylight is actually seen as being inaccurate when it comes to building regulations when there should be more appropriate terms used which are recognized by the building community and building codes.

Rooflight is another very generic term that could mean different things, but normally it can refer to a unit that is installed on a flat roof, or where it has been installed on a pitch roof which has been fitting to a tilt which levels out the tiling. Rooflights were often installed using a kerb or upstand system which is able to support the actual product and even act as a type of surface for the weathering to be attached to. When it comes to flat roof systems, the upstand is able to provide just enough height to make sure that the rooflight will stay waterproof. The rooflights will need to be installed at a certain height in order to make sure that the guarantees that are provided by the supplier for weatherproofing systems.

Roof windows are covered under a law that states that they have to be installed within the same orientation or on the in-plane of the surrounding roof, which is often at a 15-degree pitch and it must be weathered into the roof by using flashing or skirt. They are often only available in a more standardized, smaller size when compared to a rooflight. The roof windows will need to be marked by CE in order to be sold and the manufacturers are required to provide a DOP or declaration of performance in order to advise the customer how the product will be able to perform under certain types of conditions. Normally this will be able to cover the things in a test in order to simulate heavy and prolonged rainfall, monitoring air leakages to make sure that the roof window does not create any type of draft or allow dampness inside, glass deflection, and how the roof window is able to withstand any increased air pressure.

Advantages and Disadvantages

Roof Windows are quite popular and they are used widely as they are used by most major national housebuilders. Not only are they reliable, but they are strong and give you great value. The advantage of the standardized sizes and even specifications means that you can go into a store and purchase the roof window right off of the shelf. However, the main disadvantage is that they are very flexible especially when it comes to scaling. If you are wanting something larger for your roof, then a roof window may not be the best option as they only come in a limited amount of sizes. Not to mention that when they are on the inside that the framework can be seen and that adds to visual clutter. However, if it is installed on a pitched roof, they are made to fit flush to the plane of the roof and have clean lines and look great which a rooflight can struggle to match.

Rooflights or a skylight are often produced in a much larger variety of sizes, shapes, functions, and specifications. You may want to open up the whole roof that has glass that will retract or to be able to safely walk on the glass that has been installed on your terrace.

If you are needing access to your terrace, then you can get box rooflights or hinged access which allows you to have the suitable means to do so. The scope of rooflights will be much broader, but this can cause your unit to be built specifically for you, and this could take several weeks. These also continue to be much more expensive than a roof window just because of how they are made.
The manufacturers for rooflights are also now responding to the client demand for flexibility and scale, but with a much lower external profile which allows it to be installed flush with the roof in the same way that a roof window can. Many people are used to having a frameless internal view with the rooflights for flat roofs and they are wanting the same thing for a pitched roof. This means that there is now a possibility of a crossover with the manufacturers to develop larger and better roof windows.

One example of this is the Pitchglaze Roof Window from Glazing Vision. This is made using a similar technique to rooflights by using a Qualicoat type powdered coated frame. It also is made with a type of bonded glass. This means that it is a fixed roof window was created so that it would fit within the plane of the pitch. Unlike more traditional roof windows, this model is currently available up to 3 square meters, so that you will have the profile of a roof window and the scale of a rooflight, with the additional benefit of frameless internal views.