I have a 24’x40’ shop at my house that I have been thinking about adding some insulation to. Right now all the studs and rafters are totally exposed. I added an attic exhaust fan last summer and that helped a lot with the heat. I was thinking if I added insulation to the ceiling that it would also help. What would be the most cost effective way to do something like this? The rafters are on 24” centers. Do they make faced fiberglass insulation this size that I could just staple to the rafters? Or would I need to cover the bottom of the rafters with some kind of sheeting and roll un faced insulation on top of the sheeting?