Highly reliable and redundant systems.
Johns Manville is not only a pioneer in developing BUR (Built-Up Roofing) systems, but Johns Manville created the very first BUR system in America more than 150 years ago. Johns Manville’s continuous investment in developing materials and manufacturing techniques has taken that heritage to a new level, and today nearly one billion square feet of Johns Manville BUR systems are under guarantee.
Why use Johns Manville BUR (Built-Up Roofing) systems over other products?
Because few other systems are so long lasting, durable and worry free. With Johns Manville BUR systems, the highly reliable waterproof membrane is field fabricated with layers of bitumen, alternating with plies of reinforcing felts. The redundant layers give it exceptional resistance to water and weather. Johns Manville BUR systems also manufacture a complete line of fiber glass felts, including ply and base felts, and mineral-surfaced cap sheets.
Johns Manville Built Up Roof System Time Lapse Install
Energy, Environment and Roofing Engineering
Think of Johns Manville when you think of sustainable building – creating structures that preserve the natural environment, use less energy, last longer and are more comfortable to be in and around.
Many factors affect the indoor temperature of a building and ultimately our comfort as building occupants. Environmental factors such as sunshine, clouds, humidity and wind speed all impact the building envelope, causing a temperature change. The first line of defense for a building is the material selection and placement in the building envelope.
Highly infrared emissive and solar reflective roofing surfaces can help save money in air-conditioning costs because less heat is transferred into the building. Increased insulation also can mitigate this heat transfer, translating into less cooling to keep people comfortable. This is especially true on hot afternoons in peak energy periods, such as 3 p.m. in the middle of July on a 90°F (32°C) day. Lower peak usage helps to reduce the chance of rolling power outages, which means businesses stay up and running.
Role of Reflectivity and Emissivity in Cool Roofs
To better understand the concept of cool roofs, you need to understand reflectivity and emissivity. Conceptually, the sun’s solar radiation affects a product’s reflective and emissive properties.
Energy-efficient material selection will impact indoor environmental comfort, which results in lower energy consumption and reduced demand during peak periods.
Solar reflectivity (or reflectance) is the fraction of the solar energy that is reflected by the surface (i.e., roofing membrane) back to the sky. White membranes have the highest solar reflectivity, while black membranes have the lowest.
Infrared emissivity (or emittance) is a measure of the ability of a surface to shed some of its heat (in the form of infrared radiation) away from it (i.e., roofing membrane). High infrared emissivity helps keep surfaces cool. This property can make a significant difference in controlling the “urban heat island effect.” Metallic surfaces have a low infrared emissivity.
Solar Reflective Index (SRI)
The Solar Reflective Index is a measure of the constructed surface’s ability to reflect solar heat, as shown by a small temperature rise. It is defined so that a standard black (reflectance
0.05, emittance 0.90) is 0 and a standard white (reflectance 0.80, emittance 0.90) is 100. SRI combines reflectance and emittance into one number.