We recently had a 16 x 16 patio room built. It is a wood frame type enclosure. I installed energy efficient windows and plan to use batt roll insulation in the walls and ceiling. The room is mostly windows on three sides. Is it worth the time and expense to additionaly use foam board type insulation over the roll insulation on the interior walls and ceiling? Is this over kill? No insulation was used for the exterior walls. The exterior was covered with fiberboard type siding only. I live in Central Texas and it gets pretty hot here in the summer. Thanks in advance for any help with this question.

Is the room heated or air conditioned? If not, why insulate at all?

If you do insulate, be careful of creating two vapor retarders, and be certain that even if only one vapor retarder is created, that it is correctly located within the wall assembly. It is possible that in your region, the vapor retarder should be on the outside of the wall. Consult a local knowledgeable person, be it an architect, heating and air conditioning contrator, or insulation contractor, to get an opinion appropriate for your region.