Hi--A friend of mine and I are converting a building into a studio type cottage-one room-16 ft X20 ft. in North Florida=In winter temp veries from 55 to 75 during the day to 25 to 55 at night during summer hot and humid day and night. I'm wondering if there is any way I can leave the ceiling open with rafters exposed and just bare plywood-I have a shingle roof and there are vented soffits on front and back==I'm not really worried about heat loss through the celing but someone told me if I go away for the summer months and leave it closed up I will have a mold problem--would leaving ac on low or dehumidifier or ceiling fans or gable vents prevent this? Can ceiling be left without any type of airspace with bare plywood or does it have to be insulated? Please help-I only have one day left to make up my mind! :)

Gable vents and ceiling fans would probably solve the problem with the mold allowing better air circulation. Insulating the rafter space probably would have no effect as far as the mold issue. If you wanted to insulate for temperature control, I would leave at least a 2" space between the roof sheething and the insulation and also install a ridge vent to allow the roof to breath. Hope this helps.

I'd agree with nike but can add my 2 cents. You need to tell us how you want your finished ceiling to appear if you are going to insulate. I think you possible have confusedthe terms soffit and roof peak vents, the soffit is inside the eave at the lower edge of the roof.

I agree. More info needed. I just gutted out my 1.5 story Cape Cod in NY. Insulation is a must up here. I went with Icenene spray foam and it's already paying off in lower heat bills. I know heat loss is not a concern of yours... but what about heat gain/ AC loss? Without insulation, the room might start to bake. The upstairs did in my house. That's why I gutted it and added insulation.

Good point logan, cost of cooling can be as high as our cost of heating. Insulation and roof ventilation are a must to have economical comfort.