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INSTALLING AND SIZING SKYLIGHTS

 
   

There are good alternatives to traditional rectangular skylights, namely tubular skylights. These skylights are cheap, and may provide excellent daylighting (but no views or ventilation). Besides, they are small and easy to install.

See: Tubular skylights installation.

Traditional rectangular skylights may provide good lighting, and also views and natural ventilation, but they are more complex to install and the question of size is an important one.

See: Traditional rectangular skylights


Traditional skylights size

The physical size of a rectangular-traditional skylight is critical. Skylights do not need to be large to provide the wanted daylight. In rooms where the windows surface is reasonable, the skylight size shouldn’t exceed 5% of the room’s floor area; in spaces with an insufficient surface of windows it shouldn’t exceed 10-15% of the room's floor area.


Skylights position

To maximize day-lighting, take into account the position of the skylight on the roof.

Skylights on roofs that face north (or south, in the southern hemisphere) provide a cool and rather constant illumination, while south-facing skylights (or north-facing ones, in the southern hemisphere) provide more daylight (and heat gains) than any other position (which however may be rather unwanted in the summer).

As to skylights on east-facing roofs, they provide maximum light (and also solar heat gains in the morning), while west-facing skylights provide that maximum in the afternoon.

To prevent unwanted solar heat gains, there are skylights with special glazings (not to talk of tubular skylights….). Other options include the shade of deciduous trees and coverings or films on the outside or inside of the skylight.


Slope

In the case of traditional skylights, its slope affects its lighting performance and mainly the solar heat gains. A low-slope isn’t a good option: it will cause less heat in the winter and more heat in the summer.

To overcome that, some manufacturers offer skylights allowing the increasing in their angle above the roof. A good rule of thumb is to achieve a slope equal to the geographical latitude of the house plus 5 to 15 degrees.


Tubular skylights installation

The installation cost of tubular skylights is lower than that of conventional skylights, mainly because they demand reduced modification in the home’s structures or in their framing and additions, and are particularly easy to fit between rafters and other elements (due to their dimensions and lightweight).

Tubular skylights can be installed in a few hours, in a rather simple way: usually it involves a 10 to 21 inches hole (the diameter of the reflecting tubing) in the roof and interior ceiling. Tubing is usually easy to pass between roof rafters and trusses, and due to its lightweight the system can be easily mounted on the roof and interior ceiling without any additional support - the tubing is attached to the collector (mounted on the roof) and to the interior wall-surface, while the diffuser is installed to the end of the reflecting tubing.

Tubular skylights are particularly suitable on pitched roofs (above attic spaces), but they are also suitable on low-slope roofs.


Traditional skylight installation

When installing a traditional skylight, follow the manufacturer's guidelines. And have a professional to install it. A proper installation is crucial to avoid water leaking and to ensure the maximum energy performance.

To avoid water leaks, follow the manufacturer’s guidelines and take into account some basic rules:

- The skylights should be mounted above the roof surface (and not on it);
- The installation should consider a curb (in order to channel the rainwater away from the skylight);
- Also consider a flashing and seal the joints carefully; and consider a layer of sheet waterproofing (over the flashing and the flanges of the skylight, to avoid ice dams).


Skylights & Deciduous trees, Window coverings and other devices

Besides special glazes to control solar heat gains, the use of deciduous trees or coverings (inside or outside the skylight), exterior awnings or reflective films
(applied in summer to reduce overheating problems) can also be important for solar heat gains control.

For more information:
Trees, House, Landscape
Awnings, screens and other devices
House, Climate, Shadow




 




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