I live in a Brooklyn, NY brownstone and I have two emergency exits in my basement...one is the exit towards the front of the house and is covered from the outside by a metal shed and is the size of a regular doorway. The other is the exit towards the backyard and is also covered by a metal shed but is a square half the size of a regular door opening. There's nothing covering these openings from the inside and it's easy for bugs to get into the basement and it's not very economical as far as heating is concerned. What can I install to cover the openings and still keep the emergency exit?