Fixing Radon Problems
If testing shows a higher than acceptable level, there are numerous strategies for fixing a radon problem:
Passive Sealing
Theory: Find out where it is coming in. Block those pathways and it can't come in any more.
Effectiveness: Dicey. Can be effective if there is a single, well defined source like a sump. Otherwise you wind up chasing the problem around.
Typical cost: $250
Soil Depressurization
Theory: Create a vacuum in the soil under the building, drawing off gases before they reach the envelope. Ideal is to draw through the perimeter "draintile" rather than trying to protect the entire footprint with one or two collection points.
Effectiveness: Active (fan-driven) systems are guaranteed. Homes with perimeter draintile and/or loose soil work best, and can usually be brought to below 2 pCi/l, approaching outdoor air. Passive stacks, which depend on warm air rising, are nice in theory, but not very effective.
Typical cost: $750
Reverse Flow
Theory: Create a bubble of fresh air in the soil under the building, pushing soil gas away instead of drawing it off. Hence the name.
Effectiveness: Unpredictable, can be very effective. Needs very loose soil and careful sealing (otherwise could make matters worse).
Typical cost: $600
Basement or Crawlspace Pressurization
Theory: If the basement is at a positive pressure relative to the soil, no air can leak in.
Effectiveness: Difficult to create and maintain adequate pressure in some homes.
Typical cost: $300
Heat Recovery Ventilator (HRV)
Theory: Energy-efficient open window. Bring in plenty of fresh air, and the radon concentration will be reduced. Balance the system to provide slight pressurization.
Effectiveness: Not practical for reductions of more than about 50 percent.
Typical cost: $1,500
Cap the Stack
Theory: Reduce the "stack effect" by blocking airflow from top floor into the attic. Imagine putting your finger on a straw and then immersing it; as long as you have capped it, water can't enter.
Effectiveness: Not recommended as a primary strategy, but if being done as part of an energy improvement plan, or to isolate vermiculite, will be helpful.
Typical cost: $100?
Visit the links on the left for additional detail and some examples.
Find qualified contractors and avoid being stung by a scam artist. Hint: Look for cute wording intended to make you think the company is experienced. Definitely don't believe the yellow pages!