Rain Coat Fabric Rating ?? need help

1. http://www.outdoorgear.co.uk/infopoint/definitions/hydrostatic.htm

2. http://en.wikipedia.org/wiki/Waterproof_fabric

For the waterproof fabric rating yes higher is better. I believe a rating of 10,000 to 20,000 is necessary for a fabric to be labeled as waterproof. I don't know if that is a USA rule or an industry standard.

Basically this number represents the depth of a column of water that the fabric can suppport before the fabric leaks. It can be measured by attaching a piece of fabric to the bottom of a tube and then slowly filling the tube with water. The distance from the top of the water to the fabric in millimeters in the waterproof rating.

As to the breathability rating the higher the number the better. However there are may different ways of measuring this and no one can agree on the best method. The number is meaningless without knowing the test method used. Some methods will generate higher numbers than others. So without knowing the details of the measurement method you cannot know which fabric has the beast breathability by looking at the numbers.

For example one simple way of measuring this is to put water in a heated container and then cover the container with the fabric and then measure the water loss over a periode of time. If you do this with a air gap between the fabric and the water a fabric like Event will give you a high number (and see steam comming off of the fabric) while a waterbroof breathable Polyurethane fabric would have much lower numbers(and no visible steam). However if you turn the glass upside down (water in contact with the fabric)the polyurehane fabric will perform almost as well as Event. Outside of the lab the fit, construction of the jacket, weather conditions, and the physical activity of the person will have a big impact on how well it breaths.

Backpacking light has a good artical about this (dated 2004)http://www.backpackinglight.com/cgi-bin/backpackinglight/00316.html

The artical shows data for a number of fabrics and Event and Toray Entrant G2 XT were listed as the most breathable at the time.