Weather Tight Ventilator Weather Tight Ventilator MarineHVAC (Mechanical) (OP) 30 Jun 14 01:48 I am very sure that the certificate for the water tight doors and weather tight doors are necessary to submit to class. But kindly advice about the weather tight louver. Do we need certificate? RE: Weather Tight Ventilator chbrow10 (Marine/Ocean) 22 Aug 14 08:46 Louver for HVAC? No, you need to demonstrate to the regulatory body that is meets their requirements. Is this USCG? You should be aware that the first 10 feet beyond the louver should be stainless steel duct or at least sheathed/clad in Stainless. This isn't a requirement, just a best practice.