New Construction Radon
Radon-Resistant New Construction and Passive Systems
The best time to control radon is before the slab is poured and the walls are closed. A well-designed rough-in can create a continuous soil-gas collection zone, provide an accessible vent route, preserve a safe fan location, and make future activation straightforward. A poorly planned rough-in can become a pipe that looks reassuring but does not communicate with the foundation it is supposed to protect.
Drennen works with builders, contractors, designers, and homeowners from plan review through final testing. Colorado licensing applies to professional radon work, while the exact new-construction code and inspection requirements depend on the local jurisdiction and project.
A passive radon system does not guarantee a low test result. The completed building must be tested, and the system may need a fan or corrective work before occupancy or after a later test.
Passive, Active, and Rough-In Systems
Rough-In Components
Collection material, a suction or vent connection, vertical piping, labels, a future fan location, and electrical provisions are installed so the system can be completed later.
Passive Radon System
The stack relies on natural temperature and pressure differences rather than a fan. Performance varies with construction, weather, route, and foundation communication.
Active Radon System
A continuously operating fan creates controlled negative pressure beneath the slab or membrane. Active systems are usually more predictable and are selected when testing or project requirements call for them.
Colorado Standards Used for New Construction
Colorado currently incorporates RRNC-2020 for rough-in components in new one- and two-family dwellings and townhouses, CCAH-2020 for reducing radon in those completed buildings, and CC-1000-2018 for new multifamily, school, commercial, and mixed-use buildings. The specific editions named in 4 CCR 754-1 control unless the state updates the rule.
The Seven Critical Design Decisions
- Map every ground-contact foundation zone before the footings and slab divide the building
- Choose a collection method that remains continuous beneath the area being served
- Plan a gas-control barrier and seal strategy that can be inspected before concealment
- Select pipe size and number of systems based on the applicable standard and served area
- Reserve a continuous chase that later trades cannot block, cut, or repurpose
- Locate the future fan outside conditioned or occupiable space and keep it serviceable
- Plan safe discharge, electrical power, alarm or monitoring, labels, testing, and turnover documents
Typical Construction Sequence
- 1
Before foundation work
Review the plans, foundation sections, additions, crawl spaces, sump, drains, utilities, chases, roofline, electrical plan, and local inspection requirements.
- 2
Before the slab
Install clean aggregate, collection mat, perforated piping, or the specified soil-gas plenum. Protect the stub and document concealed work with photographs.
- 3
At barrier installation
Complete slab sealing details or the crawl-space membrane assembly. Coordinate with waterproofing and drainage so radon control does not create moisture problems.
- 4
During framing
Run the stack at the planned size and route, label it, preserve clearances, support it, and reserve the future fan and electrical location.
- 5
At exterior or roof completion
Complete a compliant discharge and weatherproof penetration. Avoid soffits, windows, doors, decks, balconies, and other re-entry locations.
- 6
Before turnover
Test the finished building under the applicable licensed measurement protocol. Activate or correct the system if the result or local requirement calls for it.
Why Passive Systems Fail
Incomplete collection
The stack reaches only a small pocket of gravel or misses an isolated slab or crawl zone.
Blocked communication
Footings, grade beams, thickened slabs, foam, or construction debris prevent air movement to the suction point.
Leaky crawl barrier
The membrane is loose, torn, unsealed, or disconnected from the collection system.
Poor route
The stack is undersized, excessively offset, crushed, filled with condensate, or terminated where a future fan cannot be installed safely.
No testing
The property is assumed safe because a pipe exists, so elevated radon is discovered years later or during a sale.
Buying a Home With a Passive Radon System
A visible PVC stack or radon label is not proof that the system is complete. Ask for plans, concealed-work photographs, the licensed professional, system documentation, final test result, and any activation or repair history. Have the home tested even if the passive system has never had a fan.
Frequently Asked Questions
Plan It Before It Becomes a Retrofit
Drennen can review drawings, coordinate foundation zones and trades, inspect concealed components, complete passive or active systems, test the building, and provide turnover records.
Request New-Construction Radon PlanningReviewed July 2026. Confirm the current Colorado rule, incorporated standards, local code, project specifications, and inspection requirements before construction.
Drennen Custom Contracting | Serving Fort Collins and Northern Colorado | 970-482-9100 | [email protected]