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Exterior Rolling Shutters Versus Interior Shading Devices
Helmut Blum, Engineer, European Rolling Shutters,
explains the differences between the effectiveness of shading on
the inside of a window versus shading on the outside of a window
using rolling shutters.
The sun is shining, the temperature
is 100 degrees F! But you are sitting in the living room, nice and
cool, because your living room window is shaded by a big tree. One
day the tree has to be cut down. The unobstructed sun now beats
against your unprotected window, the heat in the room becomes
unbearable...what can be done to remedy the situation?
EXTERIOR ROLLING
SHUTTERS
There are, of course, mathematical
reasons and formulas for everything; but keeping this in terms
easy to explain will help those not involved in the industry to
understand what is actually happening.
Ultraviolet light comes from the
sun, penetrating the atmosphere until it eventually hits your
windows. How can you reduce the heat in a room? There are several
methods currently used to reduce sunlight from overheating rooms:
double-pane windows, interior blinds, interior or exterior tinting
and finally, exterior shading devices. To understand how and why
some applications are more efficient than others we must take a
look at some of the scientific information...
Ultraviolet light is shortwave
light that cannot be seen by the naked eye, it is able to
penetrate glass but not solid materials (blinds, plantation
shutters, tints, etc.). However, even if the ultraviolet light has
been stopped by these blocking devices it will still heat the
blinds, which in turn will heat the window and therefore penetrate
the room. This is because the energy from the light which has
heated the shading device turns the air between the window and
shading block into hot air which cannot escape to the outside of
the window. Hot air then creates a natural vacuum which cooler air
replaces and so on, until the room is circulating with
increasingly warmer air, exemplifying the need for interior air
conditioning.
We now understand that it is
important on which side of the window shading devices are placed
(as energy will turn into heat). What about the shading
coefficient of a material? This number 'is defined as the amount
of light that can or cannot penetrate an object. Shading
coefficients are defined in the realm of 0 to 1 (1 being no light
penetration). Rolling shutters have a shade coefficient of 0.03
(almost pitch dark). Rolling shutters that are attached inside to
a single windows will conduct the same energy as described above;
although there should be a gap in which wind can enter, so (a
minimal amount of) heat will be drawn away from the window.
However if applied to the exterior, they block the ultraviolet
light from getting to the window and therefore stop heat from
accumulating inside the building.
Rolling shutters on the outside of
a window also offer many other values to your building. With a
shading coefficient of 0.03 they reduce light transmission into a
room saving furniture and carpet from premature fading due to
damaging ultraviolet light. They also reduce sound transmissions,
adding a sense of security when you're away from your building, by
not only blocking out ultraviolet light but also prying eyes. |
