I am in the process of refurbishing a 1930's 3 bed semi. There are three fireplaces in the house, two downstairs and one up. One on each floor has been blocked in with plasterboard and skimmed whilst the second one downstairs has had the actual flue blocked with board and an air vent added, cos I read somewhere that chimneys [b]must[/b] be vented. Sadly now the vented one whistles when the wind blows and is driving me mad! What can I do to stop it and does the chimney need any venting to prevent damp?