There’s a lot of information out there on choosing the proper shading solution. A Google search for the term “how to choose window treatments” brings up more than 1.8 million hits. Searching the term how to choose window shades” gets even more results—almost 3.5 million!
While much of the information you find this way is good—and some of it very good—oftentimes there are key elements missing. In some cases, the advice can actually lead to making a poor choice under certain conditions.
I was reminded of this a while back when I came across a blog post by one of our shade dealers, John Edwards of Window Products Management.
In his post, entitled “When Specifying Window Treatments–This Is The Most Important Information You Probably Don’t Know,” John recalls a training session where some incorrect information was given about using shades to control solar heat gain. The person leading the class—which was AIA-certified—told the class that when controlling solar heat gain, “the most important consideration in selecting a material is the ‘openness factor’ and that the tighter the weave, the greater the solar control – all the while holding up a piece of black shade material.”
The message the instructor was sending was that fabric color plays no role in controlling solar heat gain. And that simply isn’t the case.
Openness factor certainly is an important factor in reducing solar heat gain. Openness factor is the percentage of space in the weave of a shade fabric. The smaller the openness factor, the less light gets through. The higher the openness factor, the more space there is. Obviously the higher the openness factor, the better the view-through characteristics will be. However, that also means more solar radiation getting through into the room.
However, color also has a major impact on solar heat gain. Energy from the sun is short wave and carries little heat. Heat is only produced when the solar energy is absorbed by a surface such as carpeting or furniture and is radiated as long wave infrared (IR) energy. Generally dark fabrics absorb solar heat. The darker a fabric is, the less solar radiation is reflected. So, if controlling solar heat gain is your main concern, dark shade fabrics are not going to be nearly as effective as light colored fabrics. While there is an advance from Mermet called KOOLBLACK, which brings the better reflectivity of light colors to darker ones, in general this will hold true.
There are other considerations to make as well, depending on what you want to accomplish. You can read our white paper on the subject of choosing the best shade fabric by clicking here.
You can read John’s post by clicking here.