Low to Moderate - Professional installation is highly recommended to ensure system effectiveness, safety, and compliance with all local and national building codes.
Installation of a Sub-Slab Depressurization (SSD) system involves specialized knowledge across multiple trades including general building construction (slab work, penetrations, sealing), mechanical ventilation (fan sizing, duct routing), and electrical (fan wiring, disconnects). Ensuring proper sub-slab depressurization and effective radon mitigation requires adherence to specific air flow dynamics. Improper installation can lead to ineffective mitigation, energy loss, or safety hazards. This complexity, coupled with stringent DuPage County adopted building codes (2024 IRC, 2023 NEC), necessitates a professional approach.
Project Guidelines & Rules
General Requirements & Permitting
3 Rules
Permit Application and Inspections: A permit shall be obtained from your local building department prior to the installation of any sub-slab depressurization system. All required inspections (e.g., rough-in, final electrical, final mechanical) shall be scheduled and passed.
IRC R105.1, R109.1
System Purpose: The system shall be designed and installed to create and maintain a negative pressure field beneath the concrete slab to effectively mitigate radon gas entry into the building.
IRC Appendix F (AF102)
Installer Qualification: Installation shall be performed by, or under the direct supervision of, a qualified professional experienced in radon mitigation and familiar with DuPage County adopted codes.
IRC R104.1 (Authority of Code Official)
Sub-Slab Preparation & Suction Point(s)
4 Rules
Sub-Slab Aggregate Layer: A minimum 4-inch (102 mm) layer of clean, coarse aggregate or equivalent gas-permeable material shall be present beneath the slab to facilitate gas collection.
IRC AF103.2
Suction Pit/Point Construction: A sealed suction pit, minimum 5 gallons (19 L) volume, or a sealed pipe directly inserted into the aggregate layer, shall be provided to ensure effective and uniform gas collection beneath the slab.
IRC AF104.2
Slab Penetration Sealing: All penetrations through the concrete slab, including the suction pipe, shall be sealed airtight using a non-shrinking caulk, polyurethane foam, or other approved, durable sealant. Existing cracks and openings in the slab shall also be sealed.
IRC AF104.3
Foundation Wall & Exposed Earth Sealing: All accessible openings in foundation walls (e.g., mortar joints, utility penetrations) shall be sealed. In crawl spaces, exposed earth shall be covered with a continuous 6-mil (0.15 mm) polyethylene sheeting or approved equivalent and sealed to the foundation walls and all penetrations.
IRC AF104.3
Piping & Venting
4 Rules
Pipe Material & Diameter: All piping shall be Schedule 40 PVC or equivalent rigid nonmetallic pipe suitable for gas handling, with a minimum nominal diameter of 3 inches (76 mm). All joints shall be solvent-welded.
IRC AF104.4
Pipe Routing & Support: Piping shall be routed as directly as practicable from the suction point to the exterior termination. All horizontal runs shall be sloped back towards the suction pit to prevent condensate accumulation. Piping shall be securely supported at maximum 4-foot (1219 mm) intervals.
IRC AF104.5
Condensate Prevention: Where piping passes through unconditioned spaces (e.g., attic, unheated garage), insulation shall be provided to prevent condensation. Any condensate drainage, if necessary, shall discharge in a manner that does not connect to the sanitary sewer system or create other hazards.
IRC AF104.6
Vent Termination - Above Roof: The vent pipe shall terminate at least 12 inches (305 mm) above the roof line, and at least 10 feet (3048 mm) horizontally from any window, door, or other opening into the conditioned space of the building, and at least 10 feet (3048 mm) from any adjacent building. The termination shall also be at least 2 feet (610 mm) above any roof or wall opening within 10 feet (3048 mm) horizontally. Proper roof flashing and weatherproofing are required.
IRC AF104.7; M1503.4; M1503.6
Fan & Electrical
5 Rules
Fan Type & Location: The radon fan shall be specifically designed for continuous radon mitigation and listed for its intended use. It shall be located in an unconditioned space (e.g., attic, garage, exterior) or in a space not continuously occupied. It shall not be located in a habitable space or where it could draw conditioned air from the dwelling.
IRC AF105.1
Electrical Connection & Disconnect: The radon fan shall be wired to a dedicated electrical circuit with an accessible disconnect switch located within sight of the fan or on the same floor level. The circuit shall be protected by an overcurrent device in accordance with NEC Article 240.
NEC 430.102; 430.103; 240
Wiring Methods: All electrical wiring shall be installed in accordance with NEC Article 300, using approved wiring methods appropriate for the location (e.g., Romex in accessible areas, conduit where exposed to physical damage or outdoors). All junction boxes shall be properly covered.
NEC 300
Grounding & Bonding: The fan motor and entire electrical system shall be properly grounded and bonded in accordance with NEC Article 250.
NEC 250
GFCI Protection: If the fan is installed outdoors, in a garage, in a basement within 6 feet of a water source (e.g., utility sink, water heater), or any other damp/wet location as defined by the NEC, the circuit serving the fan shall be provided with ground-fault circuit-interrupter (GFCI) protection.
NEC 210.8
System Monitoring & Labeling
3 Rules
System Monitoring Device: A manometer or other approved visual pressure gauge shall be permanently installed on the vent pipe to indicate fan operation and system performance. It shall be located in a visible area easily accessible to the homeowner.
IRC AF107.1
System Identification Label: A durable label shall be permanently affixed to the vent pipe in a conspicuous location, identifying it as a 'Radon Mitigation System' and including warnings such as 'Do Not Obstruct' or 'System Essential for Health'.
IRC AF108.1
Electrical Labeling: The disconnect switch for the radon fan shall be clearly labeled to identify its purpose as the 'Radon Fan Disconnect' or similar.
NEC 110.22
Sealing & Firestopping
2 Rules
Firestopping at Penetrations: All penetrations through fire-resistance-rated assemblies (e.g., floor/ceiling assemblies, firewalls, shaft walls) for the radon piping shall be firestopped with approved materials to maintain the integrity of the fire-resistance rating.
IRC R602.8
Air Sealing of Building Envelope: All penetrations of the building envelope, including around the vent pipe at the roof and any exterior walls, shall be sealed to prevent air leakage, maintain energy efficiency, and prevent moisture intrusion. This includes proper flashing at the roof penetration.
IRC R402.4.1 (Building Thermal Envelope)