Carlisle, Mass., farmstead: work on the living room-hall fireplace, the front porch and the well. Host Kevin O'Connor visits another timber-frame barn refurbished on the show, this one in Concord, Mass., to see how the homeowners like it. On “Ask This Old House,” contractor Tom Silva helps a Massachusetts homeowner install storm windows and plumber Richard Trethewey examines carbon-monoxide detectors with a New York City homeowner. Also: landscaper Roger Cook on preparing shrubs for winter.