I am repainting a familyroom sheetrock previously painted walls with Benjamin Moore Regal flat latex paint. Since the weather outside is very cold I heated the room to 70 overnight. Also, since the walls have been prevoiusly painted and the new paint is the same color I did not use a primer. All the walls were room temp to the touch and the interior walls painted very evenly when finished. The one long wall that has an unheated garage on the other side was very uneven and "blotchy" when finished even with two coats. This unevenness is only very noiticable when viewing the wall closeup and at a very side angle, so the problem is not very noticable. Also, I used a 3/8" nap roller cover. Before I do anymore painting in other rooms this time of year I would like to understand more about the problem to avoid it again. Is it very cold weather on outside walls even with a well heated interior? Low humidity this time of year with extremely low outside temps? Thanks for any advice.