Sunshine is the energy source that makes life on Earth possible—growing plants and animals, making the weather that brings warmth and moisture and providing health benefits for the human race. We depend on the sun for sustenance and nearly all that is beautiful. Sunshine is indeed a friend to mankind and has been since the dawn of time; however, sunshine entering a home or building is a marvel of the modern era.
Although small glass panes were fashioned into true divided light windows during the Renaissance (1400 to 1700), it was during the subsequent Baroque Era (1600 to 1800) that larger sheets of glass were developed via the plate glass method, which produced wavy and semi-clear glass.
Bringing unencumbered sunshine indoors was made possible by the invention of the float glass process. In its formation, the molten glass moves out of the melting furnace along the surface of a completely flat molten metal, causing the glass to be flat also. Because the glass does not touch any hard surface during the annealing, or hardening, period, the natural forces of surface tension and gravity bring it to a perfectly uniform thickness. Today's float glass is brilliant, transparent and nearly free of flaws and distortions—a huge improvement over glass made by other processes over the past 300 years.
Further, the electrofloat process is one in which an electric current is passed through the liquid metal to displace ions that are exchanged by those on the glass. This leaves 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-emission (low-e), screening out harmful ultraviolet (UV) rays.
Glass of the future promises to be stronger, more insulating of temperature and sound and offered in an even wider variety of colors and surface textures than we know today.
The benefits of letting sunshine into a building are many:
• Sunshine indoors is healthy for the physical body and the mental psyche, particularly when it is low-e or has an application of quality window film that screens out the harmful UV rays. Sunshine provides Vitamin D and promotes healthy body function and emotional stability. Generally, people are happier when they get some sunshine every day.
Lack of sunshine, particularly during the winter months, can lead to Seasonal Affective Disorder (SAD), which is characterized by a lethargic and depressed state. Well-placed window can bring sunshine into the homes and, more importantly, into lives.
• Sunshine through large-scale windows supplements light so that no daylighting (artificial light) is needed in many cases. This is an energy-conscious and valid reason to encourage natural sunlight in interiors. Carefully screened natural light is often preferred to artificial lighting for tasks in both business and at home.
• Natural sunshine is often full-spectrum light balanced with the cool and warm rays. Therefore it is a pure or clean light, revealing colors in their most natural or beautiful state. This means that the colors in textiles, paints and other finish materials will be at their best when viewed in an interior filled with natural light.
Artificial lighting is unbalanced—incandescent lighting is more warm with fewer cool wavelengths, making finishes appear more yellow; fluorescent lighting is typically cooler and will cause colors to appear more blue. Full spectrum fluorescent lamps (bulbs) are available, but not readily chosen because they are more costly.
SUNSHINE THE FOE
My mother lives in a Sunbelt city where temperatures in the summer routinely climb over 100 degrees Fahrenheit. Some years ago before the advent of e-mail, I received a letter from her with a quip I will never forget and have often quoted. She said, "I wouldn't go out to look at a flower if it did dare to bloom!" Recently I visited her and learned that she never goes shopping once the sun is out. The discomfort isn't worth it to her.
Heat, discomfort, intense brightness and glare—these are a few of the reasons why sunlight needs control in interiors to make the occupant more comfortable. There are other reasons why control and shading are imperative for livable interiors. They are encompassed in the need to protect ourselves and our furnishings against damage.
A few years ago, I presented a daylong CEU (continuing education unit) window treatment program to the Puerto Rico chapter of American Society of Interior Designers (ASID). As a part of that presentation, I invited a representative from Vista Window Films to address the group. It was enlightening not only from the technical viewpoint and justification for film's effectiveness in a country that never escapes the sun's damage to furnishings, but also to learn about his wife's profession. She owned a treatment center for sun-damaged skin, treating people who suffer from skin lesions, melanoma and premature aging of the skin.
It was a glimpse into the damage that is possible to humans from the sun's harmful UV rays. Can UV rays enter buildings and cause skin damage? Assuredly they can—a justification for shading or window film in any building in which occupants are exposed to the sun indoors in routine tasks or lifestyles.
The invisible UV rays, along with heat build-up also cause irreparable damage to furnishings. UV rays cause fading of artwork, upholstery, all interior textiles including rugs and carpeting. Wood floors and furnishings also are damaged by sunshine and heat—they dry, split, crack and fade. Clearly, there is a need to protect them by shading.
SHADING AND PROTECTION
Most heat and UV rays are admitted into an interior through radiation, the waves that make up sunlight. The most effective method against sunlight damage is to prevent the sun's rays from striking the glass.
Shading is the key to keeping temperatures moderate. Solar heat gain can be reduced as much as 80 percent if a window is thoroughly shaded from the outside via architectural overhangs, trees, foliage or solar screens. Quality window film (applied on the inside of the glass) also can screen more than 99 percent of the harmful UV rays, decrease temperature and help prevent shattering if the glass is broken.
The other 20 percent of heat gain is due to convection (air movement) and conduction (transfer through materials). Awnings can reduce solar heat gain by 77 percent on east- or west-facing window and up to 65 percent on south-facing windows. Solar screens or sunscreens can block 50 to 60 percent of the sunlight striking the screen. Other exterior treatments include exterior shutters and automated rolling shutters or louvers.
The ability to deflect sunlight before it hits the glass is important because once the sunlight penetrates the glass, the long, strong waves of sunlight hit objects, bounce and weaken into shorter, refracted waves. These shorter rays are not strong enough to exit back through the glass. Instead, they bounce off the inside, building heat through the greenhouse effect. If a heavy window treatment effectively blocks the rays further, the heat build-up can reach upwards of 300 degrees Fahrenheit. This intense heat can damage the window treatment, the window frame, the paint or anything left exposed in the window area.
Many interior window treatments are effective shading devices; however, some are more effective than others. A rating system called shading coefficients helps us to understand which treatments are more valuable in preventing sun damage.
A shading coefficient rates how much a window treatment is likely to reduce the heat that has already come through the window. This composite figure is subtracted from 100 percent and expressed as a decimal. Included here is a generic chart of possible shading coefficient figures helpful in guiding you through the numbers in the specifications of your alternative window treatments and at guess-timating the shading coefficients of soft treatments. Keep in mind that the lower the shading coefficient number, the more effective it is.
R-value mean resistance to heat flow and is judged as both winter and summer insulation factors. In the winter, the measurement is how much heat is released from a building through the windows and window treatments. In the summer, it's how much heat flows in through the windows from the outside.
Some products list only a winter R-value. If a product lists only one R-value, then you can safely assume it is the winter R-value. The summer R-value will be slightly less effective, meaning the number will be two to five lower. In this case, the higher R-value is, the more effective the product.
As a comparison, a single-glazed window has a winter R-value of .88 to .89. Double-glazing is 1.72 to 1.81. Compare that to an R-19 insulation for walls and an R-35 to R-40 for well-insulated ceilings. Window treatments vary from 1.0 for thin treatments to about 10.0 for super-insulating treatments (plus the windows). Window treatments typically have summer R-values of between 2.0 and 5.0. Refer to the specifications or technical data in the pricing charts or in the back of the sample books for exact comparison.
Products offered as effective shading for glass are an increasingly important selling tool for dealers and designers, as people today are more concerned than ever that their furnishings and themselves be protected. We can help to make that happen.