Sleeping Bag Ratings and Standards Tests

Article from Mountain Equipment Co-Op

No mandatory testing standards currently exist for sleeping bags. MEC voluntarily follows a set of principles developed by the American Society for Testing and Materials (ASTM). These guidelines ensure the Co-op produces top-quality gear with consistent, dependable results. All of our bags are measured for thermal insulation value, volume, and loft in the controlled conditions.

Temperature Ratings

In an environment maintained at a constant temperature and humidity, a bag is laid on an insulated pad and occupied by a copper mannequin wired with heat sensors and warmed with an electric current. Then, the amount of electric energy required to keep the mannequin at a constant temperature is recorded and converted into a preliminary temperature rating.

What works for a copper mannequin in a laboratory, might not work quite the same for you. So, MEC also performs extensive field tests with sleeping bag prototypes. Lab and field results are considered together with the type and amount of insulation, and the bag's design, to arrive at a temperature rating.

We rate our bags conservatively, and sincerely believe our ratings are realistic for the vast majority of users in most conditions. However, human factors such as body fat, fitness, fatigue, hydration, and diet will also play a role in how warm you sleep. Like most manufacturers, our ratings assume you're using a sleeping pad and a tent. To increase the warmth of a bag, you can use an overbag or bag liner. Read Creating a Complete Sleeping System for ways to get optimum performance and versatility from your bag.

Volume

Conducted in-house, in a controlled environment, this test determines the compressed volume of our bags. The bag is unpacked, shaken for 1 minute, left for 24 hours, and then carefully stuffed into the bottom of a large plastic barrel. Next, a cylinder-shaped measuring device is placed inside the barrel, on top of the bag. Weights are piled on the measuring device until the bag is compressed with 111kg of pressure. Then the bag's volume is measured.

Loft

This test determines how puffy the sleeping bag is. Also conducted in-house under controlled conditions, the bag is unpacked, shaken for 1 minute, and left for 24 hours. A round and very light disc (of standard weight and diameter) is placed in the centre of the bag. The height between the disc and the surface the bag is lying on is measured and converted to a measurement of loft.