The show opens with a little clamming, looking for quahogs at a secret location. At the site, we meet designer Jock Gifford, who uses the model of the house to explain the work going on: cutting a hole in the roof to accept the addition's gable. Inside, we meet framing contractor Paul O'Rourke, whose crew makes the cut, assembles the gable wall on the second floor, and pushes it up into place. On the roof, Bruce Killen reviews the progress the new wood shingle roof and the ingredients that go into a roof designed to last 50 years, even in the harsh island environment: heavy roof sheathing, tarpaper, bitumen membrane along edges and in valleys, copper valleys and drip edge, a three-dimensional mesh that allows a layer of air beneath the shingles, and the shingles themselves - #1, vertical-grained, thick-butted (5/8"") Western red cedar. Homeowner Craig Bentley considers the possibility of using a ground-source heat pump to both heat and cool the building, a good choice on an island with