I-joists    Typically used as secondary framing members in floor and roof systems. They make efficient use of raw materials and allow a greater versatility in building design. I-Joists come in a variety of depths, flange grades and sizes and can have parallel or tapered profiles.    More.
Inset, chimney    Parallel to, but set in from, the side walls
Insulation, thermal      Any material high in resistance to heat transmission that, when placed in the wall, ceilings or floors of a structure, will reduce the rate of heat flow. The most commonly used material is fiberglass.
Interlocking shingles    Individual shingles that mechanically fasten to each other to provide wind resistance.