Okay, now that we have gone through all that, which door is best for your application? For doors that are very wide or very tall, your choice is limited to doors that hang by gravity. Sliding doors are used in the largest sizes. Their main disadvantage is the difficulty of sealing the edges from air leakage. They also require a substantial amount of extra opening width. Folding doors probably deserve greater attention for large openings, because they are better in both respects. In smaller sizes, swinging doors provide the best potential for insulation and sealing. Their major disadvantages is the swing clearance they require on opening. An overhead door may be the best choice for a relatively small opening. Infiltration sealing in overhead doors has improved considerably in recent years, but examine the sealing design carefully before you buy.