Sub-Slab Depressurization in Iowa City
The technical name for the most common radon mitigation method — a fan-driven negative-pressure system under your slab.
Sub-slab depressurization (ASD) is the EPA-recommended radon mitigation method for slab-on-grade homes, basement homes, and most crawlspaces. It works by creating a small negative pressure zone underneath your foundation, so radon gas takes the path of least resistance — up through the vent pipe and out above the roof — instead of seeping into your living space.
A correctly installed ASD system in Iowa City consists of:
- Suction point — a 4" hole cored through the slab, ideally near the center of the home
- Vent pipe — schedule-40 PVC routed up through the home and out the roof, with all transitions properly supported
- Inline fan — installed in an unconditioned space (attic or exterior wall) so any leak in the system can't pull radon back into living space
- Pressure manometer — a U-tube gauge that lets you visually confirm the system is running
- Roof termination — at least 12" above the roofline and 10' from any opening
Done right, an ASD system reduces radon levels by 50–99%. Done wrong (wrong fan size, fan in conditioned space, inadequate sealing), it can fail entirely or even make things worse.