My home is a 1960's brick home/split level

The walls are quite thick and are plaster like. In the winter the walls are really cold and in the summer the house is unbearable hot. I have an insulation guy coming over to blow insulation in the attic. What can I do about the walls? Would putting new windows in help? Is there such a thing as blowing insulation into the walls? I am trying to level out the heating/cooling situation and I need some help. I want to warm it in the winter and cool it in the summer. Thanks............