Host Kevin O'Connor arrives to find the new family addition framed up and sheathed using something fairly new - a coated OSB product that has the properties of a house wrap built in. Building science expert Joe Lstiburek explains why he thinks the sheathing board, when properly installed with taped seams, beats traditional methods of keeping air and water out of a building. Inside, Kevin finds general contractor Tom Silva and a major discovery - a cast iron pipe that was run several years ago straight through two structural beams in the kitchen. The fix is a new footing and lally column in the basement and new post supports in the kitchen placed to accommodate the new stove vent hood. Master carpenter Norm Abram meets window restoration specialist Alison Hardy at her shop in Peabody, Massachusetts, to see the historic window sash stripped, repaired, re-glazed and repainted. Later at the house, they will be weather-stripped and outfitted with new hardware to increase their insulating and mechanical performance. With the structure now fully repaired, Tom and Kevin take down the old wall of the ell, opening up the kitchen to the new family room for the first time.