The appeal of down comforters is that by design, they maintain your body's natural temperature. A level 1 down comforter, because of its light weight, is ideal for individuals who have warmer bedroom temperatures of around 65 to 75 degrees F.

Definition of Down

Down feathers come from the inner plumage of waterfowl such as ducks and geese. These chest feathers provide breathable comfort for the birds, keeping them cool in the summer and warm in the winter--much like an authentic down comforter does for humans.

Fill Power

Fill power is a measurement of warmth and quality in a down comforter, and specifically measures the amount of space 1 ounce of down takes up. The higher the fill power, the better insulating ability a down comforter will have.

Level 1

A down comforter with a level 1 fill power will have about 300 cubic inches of down per ounce, making it very light in weight and less fluffy in appearance. The very finest of down can have a fill power of up to 750 cubic inches per ounce, while the average department store comforter often has a fill power rating of 500 to 550.

Thread Count

Thread count is the number of threads per square inch of fabric. According to Bed, Bath and Beyond, a higher thread count provides softness, durability and will keep the down feathers from leaking out of the comforter, as well as prevent impurities from getting in.

Baffle Box Construction

Baffle boxes are a type of construction in down comforters in which vertically sewn cloth walls prevent the down from shifting and clumping. Not all down comforters are constructed with baffling, especially level 1 down, so be sure to look for this feature.

Source:

Super Comfort: A Buyer's Guide to Comforters and Bedding

Plumeria Bay: Down Comforters Warmth Guide

Bed Bath and Beyond: Down Comforters, A Product Guide

More Information:

Overstock.com: A Down Comforter Buying Guide