The Board shall render a written decision or, when no decision is called for, make written findings on the application within 45 days after the last hearing. Where the application is contested or denied, each decision shall be accompanied by findings and conclusions, together with the reasons for such conclusions. Conclusions based on any provisions of this chapter or of any act, rule or regulation shall contain a reference to the provision relied on and the reasons why the conclusion is deemed appropriate in the light of the facts found. All decisions shall be made at a public hearing.