Memory foam is generally a popular mattress type thanks to its ability to move to the contours of your body, providing incredible support, pressure relief and comfort. Memory foam is constructed from a material with millions of little holes, so the mattress surface seeps out air when you lay down or apply pressure. When memory foam is compressed, there is minimal airflow or breathability, which causes the mattress to retain your body heat very well. For hot sleepers, this is a common complaint.
Geltex mattresses are made from air-permeable foam, which is inherently breathable, allowing for cool airflow throughout the night.