Host Steve Thomas recaps with homeowner Dan Beliveau the recent Boston Zoning Board of Appeals decision that gives the go-ahead for the project's master bath addition and roof deck. With approval in hand, the work commences in earnest. This Old House plumbing and heating expert Richard Trethewey shows Steve how the new HVAC duct system will be zoned to provide maximum comfort. Historic conservator Andrea Gilmore visits the project house and assesses the condition of its brownstone lintels.