FAQ-Kategorie: Dachfenster

Roof window types

Skylights let fresh air and daylight under the roof. Basically, a distinction is made between roof windows according to the type of opening.

Hinged pivot window

Hinged pivot windows have two opening functions. The primary function is the folding position. The window sash is attached to hinged bearings in the upper part of the window frame. The window sash opens outwards up to 45° degrees. In addition, the window sashes of this hinged pivot window can also be set to a pivoted position – useful for user-friendly cleaning of the roof windows. For this purpose, the window casements can be fixed. This is called the cleaning position.

Pivoting windows

Pivoting windows are attached to the centre of the window frame by pivot joints. When opened, the underside of the window casement swings outwards. The top side swings inwards. Depending on the installation height of the living roof window, the casement is at head height when in the horizontal position. The residing roof window casements can practically be swung by 180° degrees so that the outer pane faces inwards and can be cleaned.

High-swing windows

Another variant of the top-hung roof window is called a high-swing window. The top-swing windows also only open in the swing position but are supported by a spring mechanism in the upper third of the frame. This means that the window casement does not open as far into the room. It turns in a higher range and offers more headroom.

Sliding roof windows

Another less common type is the sliding roof window. As the name suggests, the casements of these roof windows open vertically or horizontally. The window sashes are rail-guided and slide sideways, downwards or upwards when opened. These sliding roof windows are particularly interesting for large openings.

More brightness and daylight

Due to their inclined orientation towards the sky, roof windows bring in more light than vertical façade windows with a comparable glass surface. Generally, skylight installations are also significantly cheaper than dormers. With the exception of heritage protected buildings, skylight installations do not normally require planning permission.

You always need planning permission for dormers. In return, however, you gain more space and usable area.

Fresh air and daylight in the roof space

Swing windows are often used in the roof area. When the window is opened, the lower section of the skylight swings outwards, and the upper section turns inwards. The attic can be ventilated quickly and effectively. However, it should be noted that when the window is fully open, half of the casement protrudes into the interior.

Swing windows

Approved roof pitch for pivot windows: from 15° degrees to 90° degrees.

Hinged-swing windows belong to the new generation of residential roof windows and combine two opening mechanisms with flaps and swings. The window casement opens (swings) outwards up to 45 degrees. If you want to clean the roof window casement, you swing the window into the so-called “cleaning position”.

Hinged-swing windows

Approved roof pitch for hinged-swing windows:
from 20/25° to 55/65° degrees, depending on the manufacturer.

Below 15° degrees, the impermeability of the skylights cannot be guaranteed.

Roof windows – standard or customised?

Roof windows are available as standard windows and made to measure. The typical residential roof windows move within a size grid (matrix). Skylight window sizes are given according to the outer dimension of the frame. Any insulation installed is not taken into account in the measurements.

Example: The roof window is specified with an external dimension of 114 x 140 cm. Due to an all-around, 3 cm thick PU insulation on the outside of the frame, the roof window has dimensions 120 x 146 cm.

The widths of the roof windows in the standard range start at 54 cm and end at 134 cm. The length dimensions (height) start at 78 cm and end at 180 cm. Not all width/length combinations are possible.

How are roof windows operated?

Roof windows can be operated either manually or electrically.

Manual

Roof windows are opened or operated manually through a window handle at the bottom or a handle strip at the top of the window casement. Residential roof windows from the manufacturer ROTO have a so-called handle operation. Like a façade window with tilt and turn fitting, the casements are folded or turned depending on the handle position (see also Opening Types). The window handle is located at the bottom centre of the cross profile of the window casement in these roof windows. Hinged and pivoted windows from the manufacturer VELUX have two handles. The lower handle is used for folding. The upper handle for swinging the casement.

Electric

Roof windows can also be opened electrically – by a motor. Depending on the area of application of the skylight, the motors can be visibly attached to the underside of the frame (e.g. for smoke ventilation windows) or invisibly. In the case of pivoting windows, a chain motor is usually mounted in the upper area of the window frame, below the sunblind box. This motor then opens the roof window using a radio signal (hand-held transmitter) or button impulse (switch) from above and allows the window casement to rise approx. 20 cm.

The manufacturer ROTO offers a unique feature. Here, top-hung swing windows are possible, which fold the window casements up to 45° with concealed motors.

Of course, sliding roof windows are also available with electric operation on request.

The customer is king

The colour of the outer cover depends on the roof window manufacturer. Until a few years ago, RAL colour 8019 (grey-brown) was standard. Currently, VELUX uses NCS S 7500-N (corresponds somewhat to RAL 7043 – traffic grey B), and ROTO uses DB703 (anthracite) as the standard colour.

However, other RAL or NCS colours are also possible upon customer request.

Protection from rain, snow and other weather conditions

The roof window’s outer cover – also flashing frame – creates a transition between the roof and the roof window frame. The skylight is protected from the weather. Standard external covers are usually made of aluminium sheets in the corresponding standard colours of the manufacturer. Aluminium is light, inexpensive, weather-resistant and easy to clean and can be supplied in many RAL or NCS colours on request.

If copper or zinc has already been used in the roof design, the exterior covering can optionally also be made of copper sheet or titanium zinc – but at higher prices.

The glazing makes the difference

The current Thermal Insulation Ordinance (EnEV) prescribes a heat transfer coefficient (U-value) of at least 1.4 W/m²K for the entire residential roof window (U-w) for inhabited (heated) rooms. All roof windows approved for residential rooms meet or undercut this required value.

Depending on the type of glazing and the construction of the roof window, a U-w value (w=window) of up to 0.8 W/m²K is possible. Simply said, the lower the specified U-value, the better the thermal insulation properties.

U-value and more – Explanation of terms

The heat transfer coefficient measures heat transfer through a solid body (such as a wall) from one fluid (a gas or a liquid) to a second fluid due to a temperature difference between the fluids. In the case of a flat wall, it indicates the heat flow (heat energy per time) per area of the wall and Kelvin of the temperature difference between the two fluids. Therefore, its SI unit is W/(m²-K) (watts per square metre and Kelvin). As a rule, k (mainly in mechanical and process engineering) or U (mainly in construction) is used as the formula symbol.

U-Value = heat transfer coefficient

Ug (g=glazing) / value for glazing

Uw(w=window) / value for entire window

W/m²K = Watt per square metre and Kelvin

Matching roof windows

In new buildings, standard dimensions of the roof window manufacturers are sufficient. In this case, standard sizes are already selected during the planning phase according to the specifications, wishes and needs, and the roof cut-outs (change) are produced. The interior fittings, including the interior panelling on the roof windows, are done later.

Affordable modernisation of roof windows

The situation is entirely different with existing residential roof windows – installed decades ago and now in need of renewal.

The interior linings, either tiled or made of high-quality wood, are still wholly working?
The manufacturer is unknown, or the dimensions do not come close to a current standard size?
Do you only want to replace the old skylight without a costly complete renovation of the roof?

Then you will find the solution in the made-to-measure renovation windows from ROTO and VELUX.

Made to measure renovation windows always fit

Based on the “clear interior lining dimensions”, a new residential roof window is made to measure for you. These individually manufactured plastic roof windows are made to fit perfectly to your existing interior linings. Only minor adjustments to the exterior of the new made-to-measure roof window are required.

Made-to-measure residential roof windows, VELUX calls these X99, ROTO MR – made-to-measure renovation windows, thus enable you to find quick, clean and affordable solutions for replacing your old, defective roof windows.