Retrofit The act of installing something after the primary area has already been constructed. RetroHeat, for example, is a product installed between floor joists to provide heat to the floor above without taking up the flooring.Related Articles: Glossary: CaulkGlossary: Tuff CableEven When the Four Winds Blow, You'll Have Heated FloorsHydronic Heated Driveways vs. Electric Heated Driveways (Part II)Installing a Radiant Snow Melting System (Part II)