Your sunroom can get hot at certain times of the year due to solar heat gain. In particular room exposures where direct sunlight gets into the porch more easily and can heat up the room more quickly. In those cases, an insulated glass window with Low E will help tremendously. There are also higher rated Low E such as Low E 366 which block out significantly higher levels of solar heat. Other ways to keep your room cooler are with higher rated insulation in your ceiling area.