3. Assess your chill factor. You should note whether you're someone who gets very warm while sleeping. If you are, you'll want to avoid memory foam and latex, which retain a lot of heat. Spring mattresses are the coolest because they allow for the most airflow. "Good support of the back can be obtained from all different types of materials," says Haex. "The choice of material depends more on whether you sweat a lot," as well as how warm you get at night