Sub-slab depressurization (SSD) is the gold-standard radon mitigation method used by NRPP-certified mitigators. It's the technical term inspectors use — here's exactly how it works and why it's effective for Denver's Front Range geology.
Sub-slab depressurization (SSD) is the technical name for the most common and effective radon mitigation approach. If your home inspector's report mentioned "SSD" or "active sub-slab depressurization," they're recommending this system. The principle is straightforward: radon accumulates under your slab before entering through cracks and openings. SSD intercepts the gas before it gets inside.
The system works by creating a zone of lower air pressure beneath your slab than exists inside the home. A continuously running fan pulls air (and radon) from beneath the foundation through one or more suction points — holes drilled through the concrete — and exhausts it through a pipe above the roofline or away from windows. As long as the system is running, radon gas is redirected away from your living space rather than drawn through the slab.
The core components: suction point(s) drilled 4–5 inches through the slab into the sub-slab aggregate; PVC pipe (typically 3-inch) connecting the suction point to the fan; a continuously running radon fan (10–20 watts, various CFM and static pressure ratings); exhaust pipe routing gas outside; and a manometer — a simple pressure gauge that tells you the system is working without any tests or meters.
SSD is appropriate for virtually every home with a concrete slab foundation — full basements, slab-on-grade, or combination foundations. It's the system inspectors recommend, lenders accept, and the EPA endorses. If your inspection report says "radon mitigation required" and your home has a basement or slab, SSD is almost certainly what you need.
The exception is a pure crawlspace foundation, which requires sub-membrane depressurization instead. Many Denver homes have a combination — partial basement and partial crawlspace — requiring both approaches in the same installation.
Suction point selection is the most important decision in an SSD installation. We test for sub-slab communication — how freely air moves under the slab — using a simple diagnostic vacuum test at the proposed drill location. Good communication (porous gravel sub-base) means one suction point is usually sufficient. Tight soil or large isolated areas may require two.
Fan selection follows. We choose fans based on the diagnostic test results: homes with high sub-slab resistance need a fan with higher static pressure; homes with very permeable soil need higher CFM. We use fans from reputable manufacturers with 30-year warranties as standard. The whisper-quiet fan upgrade (+$200) reduces audible operation from about 55 dB to under 45 dB — roughly the difference between a normal conversation and a library.
Exhaust routing goes either through the exterior wall at foundation level, up and over the roofline, or through the attic interior. Exterior routing is most common and least expensive. Interior routing through finished walls is available for homes where exterior pipe is aesthetically objectionable, at additional cost.
Standard SSD, single suction point: $1,400–$1,800. Two-point systems: $1,800–$2,400. Fan upgrade: +$200. All installs include post-test and written guarantee.
See full published pricing →Radon flagged your inspection? We specialize in closing timelines. 48-hour install window, closing-ready documentation.
Save Your Deal →