June 2002

An EVT review | Technology Today

Technology Today not ratednot ratednot ratednot ratednot rated

An EVT review

by Mark S. Graham
Be the first to comment

Twenty-five years ago, NRCA adopted the equiviscous temperature (EVT) concept for the application of interply mopping asphalt in built-up roof (BUR) systems. Since then, this concept has become widely accepted and adopted by the U.S. roofing industry. However, it sometimes is incorrectly applied to purposes other than those for which it was intended.

If you install hot-applied, bitumen-based roof systems, it would be useful to review the EVT concept and know when it applies.


In 1977, after more than four years of research and experiments, NRCA adopted the EVT concept and issued its Technical Bulletin #2.

The research revealed that the critical property for mopping asphalt is the flow of the asphalt at the application point. The experiments proved that the ideal flow, adhesion and mopping weight for asphalt for BUR systems are achieved when the asphalt's viscosity is about 125 centistokes (0.125 Pa•s) immediately before application, such as in a mop...

To read the article in its entirety, please log in or register (registration is free).

Log in or register for FREE access to this article and other Professional Roofing online content.

Not a professionalroofing.net user?

Register now for free access
  • Full access to every article
  • Online Web exclusive information
  • Photo gallery
  • Breaking news
  • Online classified ads

Already a professionalroofing.net user?

Log in now

User name:



Login help
Click here to have your user name and password emailed to you.

Comments (0) Login to post a comment or rating
There are no comments posted.