Radon in New Construction

"I purchased a new home with radon resistant features. I don't need to test"...INCORRECT

There is no way to know what the levels of radon will be after building a new home.  There are different approaches to radon resistant construction and some builders are familiar with radon resistant features. But without proper radon mitigation training, the best intended efforts could be for nothing.  Examples of radon resistant construction are: a gas permeable layer (Usually a 4-inch layer of clean coarse gravel is used beneath the slab to allow the soil gas to move freely underneath the house), plastic sheeting (usually Polyethelene) is placed on top of the gas permeable layer to help prevent the soil gas from entering the home. The sheeting also keeps concrete from clogging the gas permeable layer when the slab is poured.  These are some of the many approaches to making a new home radon resistant, but when done alone rarely have positive results.  One of the easiest and best methods to get ahead of radon in your home is to allow for the gasses to have a natural path to travel from the soil under your slab to above your house. Putting a 3-4" gas tight PVC system running from soil through the roof is easist to hide inside your residence while the house is being built. 

Passive Systems

A very common technique used in new construction is to install a vent pipe from the gas permeable layer, vertically through the house in as straight of a line as possible to safely vent radon and other soil gasses above the house.  Airflow through the pipe is induced by routing the pipe through warm spaces, creating a draft by a natural stack effect.  This is a passive system, and when installed correctly they have shown to reduce radon levels by up to 36%.  If this system is properly designed and installed, a junction box will be located near the exit point in the roof.  This allows an inline fan to be introduced to the system if needed .  

Activating a Passive System

Passive systems use a natural pressure differential between the outside air, and the area beneath the sub slab of the home to vent the radon out of the pipe. However, there needs to be a substantial difference in pressure in order for these to work effectively which in most cases, it does not.  So how is this fixed?  Sometimes it's just as easy as adding an inline fan.  Just like radon mitigation in an established home, adding a fan helps to create suction under the slab creating a natural movement for all soil gasses to escape.  If a passive system was designed correctly, adding a fan might not be difficult or expensive and could cost as little as $150 if done yourself.  If a passive system was not designed correctly, the system might not be able to be used in mitigation, creating a need for an entirely new mitigation system and costing the homeowners $800 to over $3000.  

So what system is the best system?  One that works!  In all seriousness, one system can not be deemed better than the other if they are equally effective in lowering radon levels.  The only way to know is to test.