Why Shade from the Exterior rather than the Interior
Architects and designers in America have long preferred interior devices to shade rooms from the sun. These include: drapes, miniblinds, wide blinds, verticals, woven woods Roman shades, etc. In Europe however, another trend has been taking place for the last forty years. Largely because of higher energy cost European architects and designers have discovered the superior advantages of exterior devices to shade the sun. This trend in the past 10 years has greatly increased due to the green movement and the recognition that exterior devices can significantly contribute to significant energy savings. Retractable awnings, canopies, sun screens and roll shutters have become very common place in businesses, factories and homes due to their superior efficiency in keeping the sun’s energy outside of the building.
Exterior shading devices have often been overlooked because of their initial higher cost, the aesthetic appearance may not fit will with certain building exteriors, or just plain unfamiliarity by the architects and designers with alternative solutions. If function were the leading criterion for making the decision about how to control the harmful effects of the sun, exterior shading devices would win hands down!
The Sun’s Energy
To appreciate the advantage of exterior shading devices one must first understand how the sun works. Simply put, the sun’s energy reaches your home’s walls and windows in the form of radiation and convection. Radiation (direct sun light) is transmitted in the form of short wave radiation. Convection is transmitted by reflection and as heat in the air. Convection is long wave radiation.
When the sun light hits your home, the roof and walls will stop the energy. Your windows however cannot stop the penetration of short wave radiation. The window glass will halt the long wave radiation, but cannot stop the short wave.
Once the short wave radiation passes through the window and touches any surface inside your home, such as floors, drapes, or furniture, it is absorbed and converted into long wave radiation (heat). Sometimes this is called passive solar heat gain.
The Energy Trap
Now, if we install a shading device next to the window glass, we can stop the short wave radiation…..but it makes a huge difference where we decide to stop it!
An exterior sun screen will stop almost all of the short wave radiation before it reaches the window glass. It will reflect and absorb the sun’s energy outside of the house.
If however, we install and interior shading device, the short wave radiation will enter the room and then strike the device. The interior shading device will absorb the short wave radiation and convert into long wave convection radiation (heat). It will try to pass the heat back through the window glass. But alas, it cannot succeed. The converted radiation (heat) is trapped inside the house. There is heat gain.
What has happened you know all too well. It happens at least every bright sunny day. The house gets warmer and warmer no matter what you put on the inside of the windows.
The Exterior Advantage
The advantage of an exterior shading device is that it reflects and absorbs solar energy outside the house…before it hits the windows! The exterior shade will absorb, reflect and re-emit a total of up to 95% of the total solar radiance while only 5% is admitted into the interior space. Thus, Heat Gain is significantly reduced.
These factors will vary with weather conditions, color and type of fabric and type of shading device and the window glazing system performance. A retractable exterior shade, when rolled up will allow maximum heat gain at times of the year or day when heat gain is desired. Such flexibility is not only cost effective, but also much more desired in today’ energy and environmentally conscious society. Some structures with large expanses of glass facing the sun have reported lower air conditioning cost by over 50% Exterior shading devices are not only environmentally friendly but can also pay for them selves in energy cost savings.
Products from abc Sun Control, LLC can help your customers overcome the Harmful Effects of the sun
abc Sun Control, LLC has a solution that is right and will fit your customer’s needs, whether residential or commercial. We have been in business for thirty years and have a proven track record. Retractable sun screens systems can be retracted when your customer wants the sun to shine in. When they want them to block the sun’s heat and glare, gust roll them down or out. They protect valuable furnishings, carpets, drapes, wood floors and fine upholstery from sun-fading while keeping the room at a comfortable temperature. Additionally, exterior solar screens allow the customer to maintain exterior visibility and enjoy the view that they paid for.