Radon Testing Before You Remodel: A Western Colorado Homeowner’s Guide

A remodel can change how air moves through your home. Learn when to test for radon before and after construction and when mitigation should become part of the plan.

A remodel changes more than finishes and floor plans. New windows, added insulation, basement living space, HVAC changes, and foundation work can all affect how air enters and moves through a home. In Western Colorado, where elevated radon is common, testing should be part of the remodeling conversation—not an afterthought once the project is complete.

Radon is a naturally occurring radioactive gas produced as uranium breaks down in soil and rock. It is invisible and odorless, so a test is the only way to know the level inside a home. The U.S. Environmental Protection Agency recommends taking action at 4 picocuries per liter (pCi/L) or higher and considering action when results fall between 2 and 4 pCi/L.

Why Test Before Construction Begins?

A pre-remodel test creates a baseline. It tells the homeowner and contractor whether radon is already entering the home at a concerning level and whether mitigation should be incorporated into the project.

Testing before work begins is especially useful when the project includes:

• Finishing or adding bedrooms in a basement
• Converting a crawlspace or lower level into occupied space
• Replacing windows and making the building envelope tighter
• Installing or changing heating, cooling, or ventilation equipment
• Cutting or trenching a slab for plumbing
• Building an addition with a new foundation
• Encapsulating a crawlspace
• Repairing foundation cracks or drainage systems

If a high result is discovered early, the mitigation design can often be coordinated with framing, electrical, roofing, and finish work. That may reduce disruption and avoid opening completed surfaces later.

How Remodeling Can Affect Radon Levels

Radon enters where the house contacts the ground: slab cracks, control joints, sump pits, crawlspaces, utility penetrations, and gaps around foundations. The pressure inside a home is often slightly lower than the pressure in the soil, drawing soil gas indoors.

A remodel can change that pressure relationship. Tighter windows and air sealing may reduce natural air exchange. A new exhaust fan, range hood, or combustion appliance can increase negative pressure. HVAC changes can move lower-level air throughout the house. Foundation work can either seal entry points or create new pathways.

None of these changes automatically means radon will rise. They mean an old test should not be assumed to represent the remodeled home.

Choosing the Right Test

Short-term tests typically measure radon for two to seven days and are useful for an initial snapshot. Long-term tests run for more than 90 days and better represent seasonal averages.

For a useful short-term result:

• Keep exterior doors and windows closed except for normal entry and exit
• Avoid whole-house fans or unusual ventilation
• Place the device in the lowest level that is regularly occupied or could be occupied
• Keep it away from kitchens, bathrooms, exterior walls, drafts, direct sunlight, and high humidity
• Do not move or disturb the device
• Follow the test provider’s timing and placement instructions

Construction dust, open windows, large fans, and frequent door traffic can invalidate normal testing conditions. Complete the baseline test before demolition whenever possible.

When to Test Again

Test after construction once the home has returned to normal closed-building conditions. HVAC systems should be operating normally, exterior openings should be complete, and heavy ventilation used for paint or flooring should be finished.

A post-remodel test answers the question that matters: what are occupants breathing in the completed space?

Homeowners should also retest periodically, after major foundation or HVAC changes, and after installing a mitigation system to verify performance. If a lower level becomes a bedroom, office, or family room, retesting becomes particularly important because people will spend more time there.

Planning Radon Mitigation with a Remodel

The most common active mitigation method is active soil depressurization. A fan draws radon-containing soil gas from beneath the slab or crawlspace and vents it safely above the roofline. The right design depends on the foundation, soil, footprint, additions, and how different areas connect.

During remodeling, a qualified radon professional may be able to coordinate:

• Sub-slab suction points before new flooring is installed
• Crawlspace membrane sealing
• Concealed vent-pipe routes through chases or closets
• Electrical service for the mitigation fan
• Roof penetrations coordinated with roofing work
• Sealing around sump pits and utility penetrations
• Access for future testing and maintenance

Simply sealing visible cracks is not usually a complete mitigation strategy. Sealing supports a properly designed system, but soil gas can find many pathways through a building.

Radon and Real-Estate or Insurance Questions

Radon is generally a health and property-condition issue rather than a sudden insurance loss. Keep copies of test reports, mitigation designs, permits when applicable, and post-installation results. These records can be useful during a future sale and help the next owner understand the system.

Western Colorado Radon Testing and Mitigation

Valley Restoration & Construction provides professional radon testing and mitigation planning for homes across Western Colorado. We can coordinate radon work with basement finishes, additions, and other construction so the system fits the home rather than feeling added on later.

Planning a remodel or concerned about an old radon result? Call (970) 964-4437 to discuss testing before construction begins.

Contact Valley Restoration or call (970) 964-4437 for help.