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Why is radon the public health risk that it is?

By · February 15, 2010 · Filed in Industry News · No Comments »

EPA estimates that about 20,000 lung cancer deaths each year in the U.S. are radon-related.  Exposure to radon is the second leading cause of lung cancer after smoking.  Radon is an odorless, tasteless and invisible gas produced by the decay of naturally occurring uranium in soil and water.  Radon is a form of ionizing radiation and a proven carcinogen.  Lung cancer is the only known effect on human health from exposure to radon in air.  Thus far, there is no evidence that children are at greater risk of lung cancer than are adults.

Radon in air is ubiquitous. Radon is found in outdoor air and in the indoor air of buildings of all kinds.  EPA recommends homes be fixed if the radon level is 4 pCi/L (pico Curies per Liter) or more. Because there is no known safe level of exposure to radon, EPA also recommends that Americans consider fixing their home for radon levels between 2 pCi/L and 4 pCi/L. The average radon concentration in the indoor air of America’s homes is about 1.3 pCi/L. It is upon this level that EPA based its estimate of 20,000 radon-related lung cancers a year upon. It is for this simple reason that EPA recommends that Americans consider fixing their homes when the radon level is between 2 pCi/L and 4 pCi/L. The average concentration of radon in outdoor air is .4 pCi/L or 1/10th of EPA’s 4 pCi/L action level.

For smokers the risk of lung cancer is significant due to the synergistic effects of radon and smoking. For this population about 62 people in a 1,000 will die of lung-cancer, compared to 7.3 people in a 1,000 for never smokers. Put another way, a person who never smoked (never smoker) who is exposed to 1.3 pCi/L has a 2 in 1,000 chance of lung cancer; while a smoker has a 20 in 1,000 chance of dying from lung cancer. Figure A compares the risks between smokers and never smokers; smokers are at a much higher risk than never smokers, e.g., at 8 pCi/L the risk to smokers is six times the risk to never smokers.

The radon health risk is underscored by the fact that in 1988 Congress added Title III on Indoor Radon Abatement to the Toxic Substances Control Act. It codified and funded EPA’s then fledgling radon program. Also that year, the Office of the U.S. Surgeon General issued a warning about radon urging Americans to test their homes and to reduce the radon level when necessary (U.S. Surgeon General).

Unfortunately, many Americans presume that because the action level is 4 pCi/L, a radon level of less than 4 pCi/L is ‘safe’. This perception is altogether too common in the residential real estate market. In managing any risk, we should be concerned with the greatest risk. For most Americans, their greatest exposure to radon is in their homes; especially in rooms that are below grade (e.g., basements), rooms that are in contact with the ground and those rooms immediately above them.

Crawlspace Makeover Service Description

By · November 20, 2008 · Filed in Industry News · No Comments »

Subfloor Insulation Removal

In order to gain access to all surfaces during remediation, the subfloor insulation must be removed. We carefully remove all of the subfloor insulation and/or foil vapor barrier, bag and seal each bag of insulation, then carry it to a landfill. Replacing the subfloor insulation is not recommended. Most building codes do not require it and it can actually cause more problems than it purports to solve. The facing on the insulation acts as a moisture barrier, so when humid air enters the crawlspace through the foundation vents or through the ground it gets trapped inside the crawlspace. This raises the humidity, the wood absorbs the moisture and starts to grow mold. This also raises the dew point which can cause condensation on the ductwork, which drips onto the floor, evaporates and causes more humidity.


When slight contamination exists, HEPA vacuuming or brushing may be all that is necessary to remove the mold spores. A HEPA filtered vacuum is used to remove the mold from the contaminated wood. The pipes and other surfaces in the crawlspace will be cleaned as well. Negative air pressure in the crawlspace will be created by exhausting air from the inside of the crawlspace to eliminate cross contamination during remediation.

Mold Treatment

After the removal of mold is done, the surface on which it grew needs to be treated to prohibit future growth from the roots of the mold. This is done by spraying and wiping the wood surfaces with a fungicide.
After the surface has been prepared by removal of mold and killing the spores in the wood, we apply a pigmented fungicide which looks like paint, but actually kills mold and treats the wood to prohibit future growth. We do this because the substrate has already shown itself to be porous enough and in a good place to grow mold. This treatment has leaves the crawlspace with an attractive white appearance carries a 10 year transferable warranty. The only exclusion would be a flood, water damage or something that would greatly increase the humidity.

Economy Vapor Retarder

We install a 6-mil polyethylene sheeting with twelve inch overlapping seams stapled to the ground covering the entire floor area wall to wall. This is adequate in many situations. This system does not cover the walls nor offer waterproof seams like the upgraded VaporLok system.


After the work is completed the crawlspace is to be inspected or tested by a third-party inspector.  These tests are not paid for by the remediation contractor because of the potential conflict of interest; however, we do request a copy of the test results for our records.  In some cases, a liability release may be signed in lieu of testing.  If testing is not conducted by the owner or authorized agent, the owner or authorized agent accepts responsibility for the conditions before and after remediation and/or restoration. Our work procedures would not change due to testing or not, but the property owner might choose to save money without holding the company liable.


A deposit of 1/3rd of the contract amount is required the first day the project is begun. The balance is due when the satisfactory post remediation verification is completed.

What is your warranty on mold remediation?

While many products may make claims to prevent or prohibit mold growth, the truth is mold can grow on any surface, treated or untreated, as long as the right conditions exist.  For example, mold does not consider ceramic tile as food, and yet mold will grow in the continually wet shower. Similarly, mold does not consider vinyl as food, yet it will grow on the siding of the shady side of a house if condensation occurs. The main three conditions for mold growth are: the presence of mold spores (and they are everywhere and measured in microns), food (mold can eat any cellulosic or organic substance, including dust), and moisture (the most controllable variable).  In most cases, if the relative humidity is kept below 60% and the equilibrium moisture content of the wood and other structural materials are kept below 20%, mold will not grow.  While we do use high quality chemicals when necessary, most of which claim to and do produce residual effects, our primary aim is to reduce the mold spore count to an acceptable level as determined by industry standards using removal methods (vacuuming, sanding, media blasting, demolition, etc.) and to address moisture and humidity controls.  Controlling moisture and humidity are the best form of residual mold prevention. The quality of our work is verified by the post remediation verification tests conducted by an outside firm after the project is completed

Why is mold growing in the crawlspace?

Mold cannot grow without moisture or high humidity, so a thorough investigation is necessary to determine the cause of elevated moisture in the crawlspace. In most cases, several minor conditions have contributed to creating a major problem:

  • Gutter and downspout extensions (a concrete splash block does not count). Here are the numbers: for every 1500 square feet of roof and inch of rain, 1000 gallons of water are channeled off of the roof. If the gutters do not catch the water, or the downspout extensions do not carry the water at least 6 to 10 feet away, all of that rain can make its way into the crawlspace
  • The drainage of the yard can slope toward the house and allow rain to run into the crawlspace
  • Condensation on the ductwork, as described above, can contribute to high humidity and water puddles
  • The condensate drain from the HVAC unit can deposit up to 20 gallons of water per day and is sometimes dumped at the edge of the foundation, or worse, into the crawlspace
  • Many surprise plumbing leaks have been found after they have created some damage
  • A crack in the foundation wall or exterior wall sealant can allow excess ground water to enter the crawlspace
  • Rain penetrations through the building envelope such as the seam where the porch joins the house, window and door openings, improperly installed J-channel on siding, inside corners, or unsealed building exteriors
  • Dryer vents have been found ducted into the crawlspace and can introduce warm, humid air in addition to the lint
  • An inadequate or nonexistent vapor barrier can allow excess ground moisture to evaporate into the crawlspace
  • Inadequate foundation vents or leaving them closed in the summer can hold excess humidity in the crawlspace
  • A low clearance crawlspace does not provide as much air space to “dilute” any excess humidity
  • An underground or wet-weather spring can be an explanation after other solutions have been exhausted