Radon is a colorless, odorless, radioactive gas. it is produced by the natural decay of radium and exists at varying concentrations throughout the Southeastern Pennsylvania region. Radon is emitted from the ground and diluted to an insignificant level in the atmosphere. Being a gas , radon can travel through the soil and into a building through the cracks and other openings in the foundation.
Radon is drawn from the soil through the foundation when indoor pressure is less than that in the soil. Radon levels are generally higher in winter due to the buoyancy of warm indoor air, furnace and fireplace drafts, and power exhaust fans. There are two effective approaches to radon management . Neither cost much so they be standard practice in new construction.
The Barrier Approach
Like a boat in water, the barrier approach keeps radon out by making it difficult for it to get in . What works to keep a basement dry also works to keep radon out. Because radon is a gas , the approach relies on infiltration-control measure such as the foundation. Waterproofing and damp proofing membranes outside the wall and under the slab are excellent barriers.
The Suction Approach
Suction systems collect radon from under the foundation and vent it to the outdoors . They do this by creating a stronger suction that that of the building itself . Suction systems are preferred where high potential for radon exists .
The systems have two parts: collection and discharge. A collection system adds little to construction costs, and the discharge system can be deferred until proven necessary . The collection system may utilize the existing moisture drainage system , or individual suction taps may be installed at the rate of one per 500 square feet of floor. A single tap, however, is adequate for a slab poured over a 4-inch layer of clean coarse gravel.