In a domestic situation, such as a centrally heated house, a system called the TOG rating is used. As this is a stable environment, we cannot realistically use this form of measurement for Sleeping Bags - there are too many external factors, which will affect the performance when outdoors. Factors such as:

• the time of year
• weather conditions
• use of a rol-mat/airbed
• individual body metabolism
• altitude

As a guide we use "Season Ratings"

1. Season June- Aug (Summer)
2. Season April - Sept (Spring/Summer)
3. Season March - Nov (Spring/Autumn)
4. Season Jan - Dec (Year round use)
5. Season Jan - Dec (Altitude)

These ratings are based on the UK only!

Roll Mats and Airbeds.

Sleeping Bags will lose a huge amount of insulation through cold ground. This is mainly due to the weight of the body crushing the synthetic, or natural, filling and consequently being unable to loft.

A simple Roll-Mat will help to combat the loss of insulation. Roll-Mats come in a variety of thickness, and degrees of warmth. Some ar even foil-coated, which is deisgned to reflect lost body heat. Roll-Mats are very lightweight, and can be easily fastened to a rucksack. They are not, however, designed for "mattress comfort".

Airbeds, however, will offer a fair degree of comfort, but are very heavy and are not recommended for backpacking.