No, a grow light does not act like a heat mat. Grow lights provide light and heat mats provide warmth by contact. Heat mats are used to help seeds sprout faster. Once sprouted, grow lights provide the light needed for seedlings to grow. Your room may already provide enough warmth for seed starting but, once sprouted, you will definitely need a light source. Traditionally we place seedlings in a sunny window which may or may not be sufficient. I prefer to use fluorescent lights or LED lights on a timer.