Among some, outside storm glazing is a contentious issue. We strongly recommend that all stained glass windows are covered on the outside with tempered or non tempered glass dependent upon the possibility of vandalism. Some churches have claimed that the amount of money spent on exterior glazing has been recovered within five years through fuel savings. All exterior glazing should be vented. We recommend glass as opposed to acrylic. Acrylic is a petroleum based product that scratches easily, discolours and becomes extremely brittle over time.