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.
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.
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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