Windows have revolutionized the way we live in our interiors. Whether the interior has a sweeping view of majestic mountains, a scintillating seascape or the family garden, our interior experiences can be aesthetically pleasing when the marvel of modern glass connects the interior environment with the exterior environment.
This living with nature’s rhythms includes the view of landscape,
a vista of the four seasons where they exist, as well as the fluctuation
in lighting conditions day and night, fair weather and stormy weather.
A view from the inside helps us feel connected with the great outdoors.
This relatively new idea of indoor/outdoor living, and the blurring
of the lines separating the two, is unique in the history of the
world, for never before has this kind of interior/exterior living
been possible. It is only within the past 70 years that indoor/outdoor
living has become a possibility, and now an almost common experience.
Today, whether it is an inspiring view through glass windows or
a passageway to the pool, yard or garden through an atrium wall
of window-doors, all the joys of living with nature are ours if
we desire and plan it to be so.
A GLANCE BACK AT GLASS
The first attempts to utilize large plate glass came in the mid-20th
century. Two technological developments made it possible: the refinement
of steel to frame skyscrapers and fenestration openings in homes
paved the way for skeletons known then as “curtain wall construction.”
This unusual term was derived from the second phenomenon of materials:
the development of float glass with amazing properties of strength
and endurance which became a skin-like covering of glass linking
the corporate office world with vistas and natural light in every
Glass is made of silica sand and other inorganic compounds melted
to a viscose or liquid state and then blown, poured or extruded.
Crown glass, broad glass, plate glass and sheet glass are somewhat
familiar terms. Today, modern glass is made through the float glass
process where a continuous ribbon of molten glass moves out of the
melting furnace along the surface of flat, molten metal causing
the glass to be completely flat and almost flawless. Because the
glass does not touch any hard surface while it is yet liquid, the
natural forces of surface tension and gravity bring it to a perfectly
uniform thickness. Today’s float glass is brilliant, transparent
and nearly perfect—free of distortions inherent in the other
forms of glassmaking.
The electrofloat process passes an electric current through the
metal and displaces ions that are exchanged with those of the glass
to leave a layer of copper or other reflecting metal on the surface.
Float glass can be produced in virtually any thickness and can be
made to be “low-e” or low emission, screening out harmful
ultraviolet (UV) rays. Glass can be reinforced in many ways, and
the variety of colors and textures gives a great deal of variety
to architectural choices.
REALITY CHECK: THE EFFECTS OF LARGE WINDOWS
Many of the wide expanses of windows that are the subject of interior
design consultation and window treatment sales are not low-e glass,
nor are they very often reflecting or tinted, insulated or one-way
glass. The vast majority of windows—both new and existing—do
not control light, screen glare, cut UV light or provide privacy.
This reality means that the very windows installed in homes to connect
the occupant to the vista of four seasons while keeping them in
the protected indoor environment, need our help to overcome the
down side of such an expanse.
The control of light is a sizable issue because with the desired
expansive view often comes an overwhelming and unlivable amount
of light. A lumen is the unit of luminous flux, measured against
the luminous intensity of one candle. A 60-watt light bulb has a
light output of 840 lumens. The brightness inherent in large windows
is measured in lux. This is the unit of illumination, equal to one
lumen per square meter. The illumination of bright sunlight outdoors
is 10,000 lux, whereas a very well lighted office is 500 to 1,000
lux and a conventional home lighting is 300 to 500 lux.
Where a wall of windows admits a large amount of lux, the intensity
of sunlight has negative impact on the physical and psychological
well-being of the occupants. The reaction may include physical and
mental fatigue (sometimes excessive or chronic), headaches and other
physical discomfort, and mental or physical irritation resulting
in irritability with other occupants. Accompanying too much bright
light is often too much heat, which brings physical distress to
the occupant; and where the sunlight is uncontrolled, the occupant
may feel somewhat victimized by the aggressiveness of the brightness.
In addition, the ultraviolet light combined with higher heat causes
irreversible damage to interior furnishings including textiles,
wood flooring, furniture and art and accessories. Textiles, wood
and fine art are especially vulnerable to fade damage. Brightness,
glare (excessive directional light) heat gain and heat/UV damage
are significant problems resulting from large windows. All may be
controlled through exterior and interior shading devices or film.
The measurement of the effectiveness of a shading device is termed
a shading coefficient. It is calculated by controlled testing in
independent testing laboratories where a shading device or window
treatment will reduce heat reduction measured as a percentage of
a total of 100 percent.
If, for example, an unmetallized white pleated fabric shade reduces
heat by 44 percent, then that number is subtracted from 100 and
becomes a decimal. So 100 - 44 = .54. In shading coeffient nomenclature
the lower the number, the more effective the shading. This means
that the light, heat and glare as well as the UV light is controlled.
The difficulty in utilizing shading devices, including fabric and
roller shades, shutters, blinds and draperies, is that many obscure
the view. One treatment that does a good job of reducing heat buildup
and UV damage is window film.
Where cold weather also is a factor the comfort of an interior can
be enhanced by reducing heat loss. Here, energy efficiency is measured
in R-value or resistance to heat loss. This is based on the British
thermal unit (Btu), or a measurement of heat loss per square meter.
R-values should be higher numbers. A comparison is that single glazing
(one layer of glass) has an R-value of 0.88 to 0.89, and double-glazing
1.72 to 1.81; whereas a typical exterior wall has an R-value of
14 and a superinsulated wall an R-value of 40.
Window treatments vary adding from 1.03 to about 11.00 with an average
of about 2.0. If the treatment has air pockets, as is the case with
cellular shades, these increase insulation for both cold and hot
weather extremes. It is evident that window treatments, even at
best, do not insulate well against heat-loss. The key for greater
effectiveness is found in preventing air flow to the glass, or in
sealing the glass with window treatments in times of cold. More
solid treatments will come closer to this ideal than slatted treatments.
One important factor remains in the treatment of large expanses.
That is the clients’ preference for view and for privacy in
order to guard against theft or physical harm. Perfect shading against
heat gain and insulation against heat loss almost always means a
loss of view. And, conversely, where the view is preserved, the
safety factor is increasingly risky.
In the ever-increasing awareness of energy conservation and sustainability,
an interior that utilizes energy-gobbling mechanical heating and
air conditioning becomes a culprit not a hero. It behooves design
professionals to help the client select the type of treatment that
will keep all these requirements for control of brightness, glare,
heat gain, heat loss and safety of property and person.
Finally, there is always a need for aesthetic performance. Whatever
treatment is chosen should not interfere with an exterior focal
point nor destroy the integrity of the architecture that frames
the view of season and nature.
SOUND CHOICES FOR WIDE WINDOWS
Blinds are still the perennial favorite with so many advantages.
These include the direction of light control either up or down,
the ability to stop the blind at any desirable point, the use of
off-center routed holes for greater privacy and the relative ease
of cleaning. They do conduct cold, so as winter insulators they
are a poor choice. The metal blinds can be pulled up out of site,
although wood and wood-like blinds are thicker and more difficult
to move out of the line of vision when fully raised.
The many uses of soft and roller shades in interiors is an excellent
approach. One key advantage of shades (pleated, cellular and, certainly,
roller shades) is that they can be raised almost completely out
of view into a small roller or headrail leaving the entire view
open. And they can be lowered to any desired position to block sunlight
or the view directly. The wide variety of styles and options make
them a recommended choice for large window expanses. Some also are
lightweight, so they work well in larger installations. Many are
custom fabricated to fit specialty shaped windows.
Occasionally, sunscreen fabrics are being used in homes with large
windows (especially motorized shades). These once were almost exclusively
for commercial use such as large showroom windows, or for contract
use such as corporate offices, for example. More and more, the fabrics
themselves are becoming cloth-like in feel and look, and manufacturers
are paying attention to colors and bringing out palettes that are
appealing for residential use.
As the old saying goes, “Knowledge is power.” Utilize
your knowledge in educating customers and helping them through the
myriad choices with a clear understanding of how to best treat window
expanses so they can live with the seasons in comfort and in control.
J. Nielson, Allied ASID, WCAA, is assistant professor of design at
Brigham Young University. She has authored several books including
Window Treatments, Understanding Fabrics and Interiors: An Introduction,
3rd Ed. Nielson is a regular
correspondent for Draperies & Window Coverings addressing the areas of fashion,
education and merchandising.