If you can see the top of your ceiling joists in the attic, you need to add insulation. Minimum blown insulation is R-30 or about 12" deep.
Solar attic fans run when the sun is shining. In winter, they help reduce moisture in the attic. In summer, they exhaust (pull) the heat out of your attic, which will reduce your energy bill, and protect asphalt shingles. Solar attic fans are installed near the ridge or peak of the roof to vent more heat in summer.
Tubular skylights bring natural, outdoor light into dark interior areas. They can save both on your light bill and your air-conditioning bill, if you presently have warm lights to be able to see in a dark room, such as a bathroom, closet or hallway. You can chose optional features in the skylights such as exhaust fan kits, lights with dimmer kits, or just lights. They come with a lifetime leak free warranty, and can be installed on any roof.