The sheets you use definitely play a role in maintaining temperature neutrality. Linen, cotton, and bamboo are all naturally breathable and will help fight heat retention. In terms of weave, stay away from flannel sheets and choose sheets with a breathable percale weave. Some synthetic fabrics also use technology such as phase-change material to keep you cool. It's important to remember that the temperature of your sleeping environment is a product of many factors including your mattress and/or topper, sheets, ambient temperature, your pillow, and your own personal body heat.