Radon and Home Renovations: Testing Before and After Major Changes

Structural changes:

• •Opening up walls or floors
• •Changing foundation configuration
• •Adding or removing walls
• •Creating new pathways for radon entry

Pressure changes:

• •Adding exhaust fans
• •Changing HVAC systems
• •Improving air tightness
• •Altering ventilation patterns

Usage changes:

• •Converting unfinished basement to living space
• •Adding bedrooms in basement
• •Creating new frequently-occupied areas
• •Changing how you use spaces

Finishing basement (most common):

• •Creates new sleeping/living areas
• •Increases time spent in highest-radon area
• •May seal radon entry points (good)
• •May reduce ventilation (bad)
• •Net effect unpredictable without testing

1. Include mitigation in renovation (much cheaper)

• •Walls already open
• •Easy to route pipes
• •Contractor already on site
• •Can hide components aesthetically
• •Shared labor and equipment costs
• •Typical savings: $300-800 vs later installation

2. Avoid costly surprises

• •Discover radon before spending on finishing
• •Don't finish space you can't safely use
• •Plan mitigation into budget from start
• •No re-work to add mitigation later

3. Design around radon system

• •Know where pipes will run
• •Plan room layouts accordingly
• •Hide components in walls or chases
• •Better aesthetic outcome

4. Protect your investment

• •Don't spend $15,000-30,000 finishing basement
• •Only to discover 740 Bq/m³ (20 pCi/L) radon
• •Then spend another $1,800-2,500 for mitigation
• •Better to know and plan ahead

When to test:

• •Before finalizing renovation plans
• •At least 2-3 weeks before starting work
• •In lowest area you'll renovate
• •In season of highest radon (winter typically)

What to test:

• •Area you're planning to finish
• •Lowest level even if not finishing it all
• •Where bedrooms might go
• •Where family will spend most time

High priority to address (≥ 148 Bq/m³ / 4 pCi/L):

• •Include mitigation in renovation project
• •Have contractor coordinate with radon professional
• •Install system while walls/ceilings open
• •Test after renovation to verify success

Moderate levels (100-148 Bq/m³ / 2.7-4 pCi/L):

• •Consider including mitigation
• •May increase after finishing
• •Better safe than sorry
• •Easier now than later

Low levels (<100 Bq/m³ / 2.7 pCi/L):

• •Probably safe to proceed
• •Still test after renovation
• •Levels could increase
• •Monitor going forward

2. Hire radon contractor early

• •Bring in before renovation starts
• •Design mitigation system
• •Coordinate with general contractor
• •Plan pipe routing and fan location

3. Coordinate timing

• •Radon work done while walls open
• •Usually early in renovation
• •Before insulation and drywall
• •After framing complete

4. Plan aesthetics

• •Hide pipes in wall chases if possible
• •Conceal fan in attic or closet
• •Match pipe color to decor
• •Minimize visual impact

Radon contractor installs:

• •Drilling through slab (if not done yet)
• •Installing suction pipe
• •Routing pipe through walls/ceiling
• •Mounting fan
• •Sealing foundation
• •Installing warning device

General contractor:

• •Provides access and coordination
• •Builds chases if needed for pipes
• •Coordinates with radon contractor
• •Protects radon system during work
• •Finishes around radon components

Benefits of combined project:

• •Pipes hidden in walls (better aesthetics)
• •No finished surfaces to remove/replace
• •Shared mobilization costs
• •One timeline for both projects
• •Final space is safe and finished

Cost savings:

• •Mitigation during renovation: $900-1,500
• •Mitigation after finishing: $1,500-2,500
• •Savings: $300-1,000
• •Plus better aesthetics

Example: Finishing 750 sq ft basement:

• •Renovation cost: $20,000
• •Radon test before: $30 → Result: 296 Bq/m³ (8 pCi/L)
• •Mitigation during renovation: $1,200
• •Post-renovation test: 37 Bq/m³ (1 pCi/L)
• •Total: $21,230 for safe, finished space

vs waiting until after:

• •Renovation: $20,000
• •Discover high radon after moving in
• •Retrofit mitigation: $2,000 (more expensive, tears up new finishes)
• •Total: $22,000 + disruption to new space

Renovations can increase radon:

• •New pathways created
• •Pressure dynamics changed
• •Ventilation altered
• •Foundation disturbed
• •Unforeseen effects

Renovations can decrease radon:

• •Sealing improved
• •Some entry points closed
• •Ventilation increased
• •Depressurization effects

Net effect unpredictable:

• •Only testing reveals actual impact
• •Don't assume levels stayed same
• •Don't assume they improved
• •Test to know for sure

When to test after:

• •Wait until renovation fully complete
• •All systems operating normally
• •Home closed up and sealed
• •Allow 2-4 weeks after completion
• •Test during heating season if possible

What to test:

• •Newly renovated spaces
• •Lowest level of home
• •Where family now spends time
• •New bedrooms or living areas

If levels acceptable (<148 Bq/m³ / 4 pCi/L):

• •Renovation didn't worsen radon
• •Safe to use new space
• •Retest every 2-5 years
• •Monitor for changes

If levels increased to ≥148 Bq/m³ (4 pCi/L):

• •Renovation increased radon entry or changed air patterns
• •Mitigation now needed
• •More expensive than during renovation
• •May disrupt new finishes
• •Still necessary for safety

If levels decreased significantly:

• •Renovation improvements helped
• •Good outcome
• •Still test periodically
• •Levels can change over time

Finished basement (most common):

• •Pre-renovation: Often not tested
• •Post-renovation: Now frequently occupied
• •Risk: Spending time in highest-radon area
• •Always test after finishing basement

Major additions:

• •New foundation area
• •New soil gas source
• •Changed building pressure
• •Test after addition complete

HVAC replacement:

• •Changed ventilation patterns
• •Different pressure dynamics
• •May affect radon entry
• •Test after new system operating

Energy efficiency improvements:

• •Home tighter = less ventilation
• •May reduce radon dilution
• •Can increase radon levels
• •Test after weatherization

Foundation repairs:

• •Disturbed soil around foundation
• •New cracks may form
• •Sealing may have improved or worsened
• •Test after foundation work

Why:

• •Basements typically have highest radon
• •Finishing creates living/sleeping space
• •Family spends more time there
• •Often adds bedrooms (long exposure)

Recommendations:

• •Test before starting (essential)
• •If ≥148 Bq/m³, include mitigation in project
• •If borderline, err on side of caution
• •Test after completion
• •Never skip testing for basement finishing

Changes that may affect radon:

• •Adding insulation
• •Sealing air leaks
• •New windows and doors
• •Vapor barriers

Why it matters:

• •Tighter home = less air exchange
• •Less dilution of radon
• •May increase concentrations
• •Not always significant, but possible

Recommendations:

• •Test before if home not recently tested
• •Test after improvements complete
• •Monitor levels after weatherization
• •Include radon in whole-house assessment

Types of repairs:

• •Crack sealing
• •Waterproofing
• •Drainage improvements
• •Structural repairs

Why retest:

• •Work may disturb soil
• •May create new pathways
• •Sealing might help or hurt
• •Drainage changes affect soil gas

Recommendations:

• •Test before if major work planned
• •Test 2-4 weeks after completion
• •Any foundation work = retest
• •Consider adding RRNC features during repair

Depends on:

• •New foundation or slab on grade
• •Connection to existing foundation
• •Whether adding basement space
• •Scope of foundation work

Recommendations:

• •Test existing home if not recent
• •Test new space after completion
• •If new basement, treat like basement finishing
• •Consider RRNC features in new construction

Why it might matter:

• •Changes ventilation rates
• •Alters pressure dynamics
• •May affect radon entry
• •Backdrafting concerns

Recommendations:

• •Test if no recent results
• •Test after new system operating
• •Ensure proper combustion air
• •Check for backdrafting issues

Why:

• •Usually doesn't affect radon
• •Not near source
• •Doesn't change foundation
• •Minimal impact on pressure

Recommendations:

• •Test if home not recently tested
• •Retesting probably not urgent
• •Focus on basement/first floor testing

Sealing checklist:

• •Floor-wall joints
• •Cracks in slab or walls
• •Pipe penetrations
• •Floor drains (ensure traps)
• •Window wells
• •Utility entries

Materials:

• •Polyurethane caulk (flexible)
• •Hydraulic cement (rigid areas)
• •Foam sealant (large gaps)
• •Proper primers for adhesion

Vapor barrier:

• •0.15 mm (6 mil) polyethylene minimum
• •Over all exposed soil
• •Overlapped seams, taped
• •Extended up walls
• •Sealed to walls

Opportunities:

• •Walls already exposed
• •Soil accessible
• •Equipment on site
• •Do it right the first time

Improvements:

• •Install exterior drainage if adding
• •Add radon mitigation features
• •Improve foundation sealing
• •Install radon-resistant features

Considerations:

• •Ensure adequate combustion air
• •Prevent backdrafting
• •Balance ventilation
• •Consider whole-house ventilation
• •Don't create negative pressure

Balance tightness with ventilation:

• •Seal air leaks (good)
• •Maintain adequate ventilation (essential)
• •Consider HRV/ERV for tight homes
• •Monitor radon after improvements
• •May need mechanical ventilation

General contractor should:

• •Understand radon basics
• •Coordinate with radon contractor
• •Protect radon system during work
• •Seal foundation properly
• •Follow radon-resistant practices

Radon contractor should:

• •Assess before renovation
• •Design system for post-renovation conditions
• •Coordinate installation timing
• •Work with general contractor
• •Guarantee results

Communication:

• •Discuss radon early in planning
• •Both contractors communicate
• •Clear scope of work for each
• •Defined responsibility areas
• •Coordinated schedule