No construction, reconstruction, alteration or demolition of any structure or significant exterior architectural feature of any listed property or property within any historic district shall be undertaken prior to obtaining a certificate of appropriateness from the Commission. No permit shall be issued by the Building Inspector for the erection of a sign or construction, reconstruction, alteration or demolition of any structure, work of art, object or area within a historic district or for any listed property except in cases coming under the exclusions in this chapter, unless the application for such permit is approved by the Commission through the issuance of a certificate of appropriateness in the manner prescribed herein.