There is always a place for a dormer window on a well-designed pitched roof. It is small in size and may have a completely different device. Why do you need a dormer on the roof and what types of this design exist? With it, you can ventilate the attic, go to the roof for technical work. For most roofs, the dormer window is the only source of daylight. However, performing important practical functions, this design can serve as a home decoration.
Dormer window functionality
Ventilation of the room today is taken to pay great attention, especially when it comes to the attic. The truss structure of most pitched roofs is made of well-dried wood. It can serve tens of years if all the conditions are created for this. The main enemy of rafters is dampness, but where does it come from under a hermetic roof? Do not forget the laws of physics: warm air flows from the rooms through the attic floor and condensate forms under the cold roof. It falls on all elements of the truss system, and only dormer windows in the attic will allow airing the room in a timely manner.
Types of dormer windows
Some countries have developed documentation describing the design of dormer windows and possible finishes. In other states rely on the competence of roofers and designers.
The variety of solutions allows today to highlight the following main types of dormer windows:
- rectangular with a sloping roof;
In most cases, the design of the dormer window that best fits the type of roof is chosen.
Particularly noteworthy are two types of dormer windows - mansard and lyucarna. If the traditional design of the dormer window on the roof implies a separate external structure, a kind of house on the house, the skylight is part of the roof. It is able to withstand high snow loads, is sealed and can have a variety of forms. The presence of built-in valves allows to equalize the pressure on a windy day, and special mechanisms for opening have been developed for airing.
Lukarna appeared in Western Europe in the Middle Ages and is a vertical frame located in the same plane as the facade of the house, and closed on top and on the sides. In the Late Gothic period and at the beginning of the Renaissance, houses with lyukarnaya were built everywhere; their owners asked architects to richly decorate this element with stucco, carved platbands. As a result, Lyukarna emphasized the status of the owner of the house, the presence of his taste. This element is widely spread in France, England, Germany, Austria, Italy and Russia. The windows-lucarnes decorated the palaces right up to the beginning of the twentieth century, being an obligatory element of baroque architecture.
Features of the design of dormer windows
A feature of the installation of dormer windows is their location between the truss beams. This is done in order not to reduce the strength of the system capable of withstanding high loads. The framework of the dormer window is being erected in parallel with the construction of the truss system. Strengthened rafter legs and beams jumpers, not allowed inset into the design. Gable frames carefully aligned, set the ridge beam. To facilitate the construction, it is sheathed with moisture-resistant plywood. Only when the structure is ready, sheathing roofing material.
The most difficult design of lyukarny as it bears not only practical, but also esthetic function. It has its own facade, roof and decorative elements. The shape of the window-lyukarny can be rectangular, triangular, arched. Roof - sloping, gable, hip or semicircular. A beautiful but complex arch places special demands on the roofing materials used in the first place. It is used on buildings with a roof of flexible or natural tiles, slate or flat metal. Lucarna windows can be glazed or closed blinds.
The dormer window should not be located on the front side of the roof; in this case, it will provide the minimum illumination of the roofing space.
The vertical arrangement of the dormer windows adds sophistication to the whole house, but it is not relevant for small roofs.
If you install two windows-lyukarny or more, then it is necessary to keep a distance of at least 80 cm between them. In the opposite case, snow will accumulate between the dormer windows on the roof. As a result, the load on the roof will exceed the calculated one, which will negatively affect the lifetime of the truss system. The snow will adjoin the decoration materials of dormer windows in places where it is not designed. Possible leakage of melt water and damage to the attic or insulation insulation material.
One of the main questions that interests the owners of attic houses, is the area of dormer windows. It is possible to provide normal natural daytime lighting only if the total area of the windows is 12-16% of the floor area of the attic. The best option would be a lucarn with one large window, but if several dormer windows are planned, then their total width should not exceed half the width of the room in which they will be installed.
In a residential area, the height of the dormer windows should not exceed 80-90 cm, and their optimum height is recommended in the range from 120 to 150 cm. It is easy to care for such a window, and the amount of light in the room will meet the standards.
Advantages and disadvantages of dormer windows
A skylight on the roof gives the building a more comfortable and aesthetically appealing look. It is simple to look after the window, and if necessary it can be used to get on the roof to install equipment, antennas or for scheduled repairs. With no flaws in the design, dormer windows will provide the roof space with natural light. This is especially important for residential mansards and operated technical premises.