Radon mitigation methods, explained with diagrams

Nearly every Salt Lake system works the same way. A fan pulls soil gas from under the house and vents it above the roof, before it can get inside. What changes is how the contractor reaches the soil under your particular foundation.

1. Sub-slab depressurization (basements and slabs)

A contractor drills through the basement floor or slab, removes a little soil or gravel to make a small pit, and seals a PVC pipe into the hole. A radon fan on that pipe pulls air from under the slab, creating slightly lower pressure there than inside your house. Soil gas then flows into the pipe instead of up through cracks, and it's vented above the roof.

EPA calls this "the most common and usually the most reliable radon reduction method", and notes that often only one suction point is needed. It works best when air moves easily through the material under the slab (Source: EPA).

In Salt Lake homes: the main decision is the pipe route. Exterior routes (up the outside wall, fan mounted outside) are usually simplest. Interior routes (closet to attic, fan in the attic or garage) are tidier outside but harder in a finished house. Either way, the fan must not sit in or below living space (Source: EPA).

2. Crawl spaces: submembrane suction

For crawl-space homes, the contractor lays heavy plastic sheeting over the dirt floor, seals it to the foundation walls, and runs a suction pipe from under the sheet to a fan. EPA calls this "the most effective way to reduce radon levels in crawlspace homes" (Source: EPA).

The less effective alternative is crawl-space depressurization, which pulls air from the open crawl space itself. EPA says it generally doesn't work as well and needs attention to furnace and water-heater backdrafting. Crawl-space ventilation (vents or a fan blowing outdoor air through) is the third option. In a cold climate it can freeze pipes in winter, and EPA rates it 0–50% (Source: EPA). That matters along the Wasatch Front.

3. Sump-pit and drain-tile suction

If your basement has a sump pit or a perimeter drain tile loop, the contractor may seal a lid on the sump and pull suction through it, or tie into the drain tile. EPA rates both at 50–99%. Sump-hole suction works best when air moves easily from under the slab to the sump (Source: EPA). A sealed sump lid still lets the pump work, but ask how the lid can be opened for pump service.

4. Block-wall suction

Older homes with hollow concrete-block foundation walls sometimes need suction inside the block cores, because radon can travel through them. EPA rates it 50–99%, but it requires sealing major openings (Source: EPA). It's less common in Salt Lake's many poured-concrete basements, but worth asking about in pre-1980 homes, which make up most of the housing in Holladay and Millcreek (Source: U.S. Census ACS).

5. New construction: passive systems and "radon-ready" homes

Builders can install radon-resistant features during construction: a gravel layer and plastic sheet under the slab, sealed openings, and a vent pipe from under the slab through the roof. Without a fan, a "passive" pipe typically reduces radon 30–70%. EPA notes it may work better in cold climates but isn't as effective as an active system (Source: EPA). If a test later shows 4 pCi/L or more, EPA notes a vent fan can easily be added to the passive pipe (Source: EPA).

In Utah, passive systems are voluntary. State code says that when a builder voluntarily installs passive radon controls, they must follow the radon appendix of the International Residential Code (Source: Utah Code 15A-3-206). So a newer Herriman or South Jordan home may or may not have a pipe. Look for a labeled PVC pipe in a utility room or garage, or ask the builder. Either way, EPA says every new home should be tested after occupancy (Source: EPA).

What doesn't work on its own

• Sealing cracks alone. It's part of most systems, but EPA says sealing alone hasn't been shown to lower radon significantly or consistently (Source: EPA).
• Opening windows. It's temporary: radon concentrations typically return to previous values within about 12 hours after you close up (Source: EPA).
• Air purifiers. EPA's list of radon reduction techniques doesn't include ordinary air purifiers (Source: EPA). Radon is a gas, and soil suction stops it before it gets in.

EPA's reduction ratings at a glance

Source: EPA, Consumer's Guide to Radon Reduction (Source: EPA).

Which one fits your home is a contractor's call after seeing it. See what each costs in Salt Lake, or call (801) 854-8750 to be connected with a licensed contractor.