Yes. The density of the top layer can impact its heat retention. If the top layer of the mattress is low density, your body will sink further into the mattress, thus making you feel warmer because your body heat will build up around you. A higher density foam mattress will offer firmer support, thus keeping you on top and allowing more air to circulate around you. So, if you want to sleep in a cooler environment, choose a high-density foam mattress.