Rabbet- A rectangular longitudinal groove cut in the corner edge of a board or plank.
Radiant heating– A method of heating, usually consisting of a forced hot water system with pipes placed in the floor, wall, or ceiling. Also electrically heated panels.
Radiation– Energy transmitted from a heat source to the air around it. Radiators actually depend more on convection than radiation.
Radon– A naturally-occurring, heavier than air, radioactive gas common in many parts of the country. Radon gas exposure is associated with lung cancer. Mitigation measures may involve crawl space and basement venting and various forms of vapor barriers.
Radon system– A ventilation system beneath the floor of a basement and/or structural wood floor and designed to fan exhaust radon gas to the outside of the home
Rafter– Lumber used to support the roof sheeting and roof loads. Generally, 2 X 10’s and 2 X 12’s are used. The rafters of a flat roof are sometimes called roof joists.
Rafter, hip– A rafter that forms the intersection of an external roof angle.