In construing the regulations established by this chapter, such regulations shall not be construed as requiring alterations in the construction or equipment of buildings or structures in existence at the time of passage of this code, unless specific provision is made to the contrary, or unless the provision is expressly made retroactive, or unless such buildings shall not have sufficient or adequate means of egress therefrom or ingress thereto, by reason of insufficient or inadequate doors, stairways, fire escapes, windows or other means of egress or ingress.