What you need to know about light We see things every day, from the moment we get up in the morning until we go to sleep at night. We look at everything around us using visible light. Visible light waves are the only part of the Light Spectrum that we can see forms a very small portion of what is called the "Electromagnetic Spectrum." The Electromagnetic Spectrum is measured in Nanometres, which are 1 millionth of a meter. The Electromagnetic Spectrum includes all types of radiation -, X-rays used at hospitals, radio waves used for communication, and even the microwaves you cook food with. The 3 parts of Electromagnetic Spectrum are of interest to us are the Ultra Violet rays that are harmful to our skin, the Visible Light waves, the light we use to see with and the Infrared waves or thermal waves that carry a large percentage of the Suns Heat.
What does this mean to roofing?   When talking about clear roofing there will generally be two terms which are used - Total light Transmission and Visible light transmission. Total Light refers to all light in the spectrum that covers visible and non visible, where as visible light only covers the light you can see. For example
	As you can see, cool-lite IV Blocks 64% of the light visible to the eye but also restricts 50% of total light tramissions such as Uv and thermal Rays