Reducing Radon In An Old Home

Reducing Radon in Existing Homes
This section gives an overview of what can be done to reduce radon levels in existing homes. Health Canada is currently developing standard protocols for the selection, design and operation of systems to reduce radon levels in homes, schools and
other large buildings.When completed, these protocols will provide homeowners and mitigation companies with detailed instructions and guidance on radon mitigation techniques. In the interim, comprehensive and technical information may be found in the following U.S. Environmental Protection Agency publications:
Radon Reduction Techniques for Existing Detached Houses – Technical Guidance (Third Edition) for Active Soil Depressurization Systems

Methods to reduce the level of radon in your home vary considerably in their complexity, long-term effectiveness and cost.

The effectiveness of any one radon reduction method will depend upon the unique characteristics of your home, the level of radon, the routes of the radon entry, and how thoroughly the job is done. A single method may be sufficient, but sometimes several methods must be combined to achieve acceptable results (especially when levels are high).

Many radon reduction measures require installation by a professional contractor or skilled homeowner. However, there are some steps many homeowners can take immediately, often at little cost. These steps might not always be sufficient by themselves, but they may give some reduction until more comprehensive measures can be implemented.

These steps include:

Close Major Entry Routes for Radon
Many openings in a foundation that may allow radon to enter a home may be small or hidden. However, some openings are large and obvious.

The reduction in radon levels that can be achieved by closing a particular entry route is impossible to predict. However, if a major opening is accessible, it is advisable to close it since some reduction in radon levels may be obtained.

There are also other benefits to closing major entry routes. Molds, odours, insects and cold drafts will find it more difficult to enter the basement. It is also necessary to close major entry routes if an active soil depressurization system is to be installed.

Major openings that can be important to seal include:

• Open sumps – Sumps can be fitted with an airtight cover. If the sump also acts as a floor drain, add a special trap to the airtight cover and slightly recess the cover into the sump.
• Floor drains – Basement floor drains can have special traps installed that allow water to drain, but prevent radon from entering the basement. These special traps are not a substitute for a sewer backup valve.
• Exposed soil – Exposed soil in crawl spaces can be covered by a barrier with sealed edges and joints. If there are major gaps in the basement floor slab (e.g., cold storage room), concrete should be poured to cover any exposed soil.
• Voids in concrete block walls – If there isn’t a solid row of block, seal voids in the top of foundation and interior load-bearing walls

Reduce Forces that Draw Radon into the Home
Research has indicated that reducing the negative indoor pressure that draws radon into a home can be an effective measure for some homes. However, there is a need for further research to reduce uncertainties about this technique. To reduce negative pressure in your home, open a nearby window to provide outdoor air when using an open fireplace. Rarely used fireplaces will not be a factor in radon entry rates. When the fireplace is not in use, make sure the chimney damper is shut. If you require a ventilation system, choose one that is balanced with a supply and exhaust, such as a heat recovery ventilator (HRV).

Incidental use of exhaust fans (bathroom and kitchen) is acceptable. Avoid continuous use of exhaust fans.

After taking steps to close major entry routes and reduce forces that draw radon into a home, more comprehensive and long-term measures to consider include:

Depressurize the Soil Around the Foundation
Active soil depressurization has been found to be the most effective and reliable radon reduction technique in existing homes. It is also the most common method used by contractors who specialize in radon reduction.

This method involves installing a vent pipe through the basement floor slab or connecting it to the foundation drain tiles through the sump. A fan that runs continuously is connected to the vent pipe. This reverses the air pressure difference between the house and soil, reducing concentrations of soil gas, including radon, next to the foundation.

The soil in a crawlspace can be vented in a similar manner by installing a sealed polyethylene or comparable membrane over the soil and venting the area beneath the membrane.

For homes with concrete block foundations, it is sometimes necessary to add suction to the block cores. If the block cores are open at the top of the wall, it is important to seal them. This will minimize the amount of heated or cooled air that is removed from the basement.

With any active soil depressurization system, it is wise to make sure that operation of the system does not cause backdrafting of combustion appliance (e.g., furnace, boiler, water heater, fireplace, wood stove). Backdrafting occurs when the room in which a combustion appliance is located is depressurized to the extent that combustion products spill into the home instead of venting to the outdoors. Backdraft testing may be done by a trained radon reduction or heating contractor.

The cost of an active (with fan) soil depressurization system ranges from about $1,500 to $3,000 including material and labour. There is also an operating cost for electricity for the fan and a modest increase in heating and cooling bills due to increased house ventilation.

When large radon reductions (80 per cent or more) are desired, active soil depressurization is almost always the recommended approach. If smaller reductions are sufficient, the remaining options described in this section may be reasonable alternatives.

Seal any Remaining Entry Routes for Radon
After closing major openings, a further reduction in radon levels can sometimes be achieved by sealing remaining entry routes. Minor cracks in foundation walls and floors can be sealed. Larger cracks require special techniques – consult your building material supplier or a contractor.

If accessible, the joint between the foundation wall and basement floor can be sealed (see figure 13). The gap around utility penetrations (e.g., water, sewer, electrical, natural gas, fuel oil) in walls and floors can be sealed in a similar manner. Sealing of all entry routes for soil gases such as radon is difficult and challenging. Proper preparation of surfaces to be caulked is extremely important to obtain an effective, long-lasting seal. Entry routes are often numerous – some may be concealed or inaccessible.

Because of these difficulties, when sealing of entry routes is used alone, you should expect only a low to moderate reduction in radon levels. A thorough job of sealing can result in 0 per cent to 50 per cent reduction in radon levels. Sealing will also improve the effectiveness of an active soil depressurization system.

The cost of sealing entry routes is highly variable. It can range from a few hundred dollars to $2,000 or more. Although the material cost is relatively low, it is very labour-intensive to do a comprehensive job. As the house ages and settles, the seals can deteriorate, and new cracks or entry routes can appear. As a result, there will be an ongoing cost to maintain the seals.

Increase Mechanical Ventilation of the Home
Rather than relying upon natural air movement to remove radon from a home, mechanical ventilation can be used. A system with balanced intake and exhaust air flows is essential so that the house is not depressurized, which may draw in more radon. This can be accomplished by installing a heat recovery ventilator (HRV).

Besides supplying balanced ventilation, a HRV will reduce the energy penalty associated with providing more ventilation to a home.

The suitability of an HRV for radon reduction is limited to situations where only modest reductions are needed. In most homes, an HRV might reduce radon levels by 25 per cent to 75 per cent. HRVs are best suited to homes that are relatively airtight and have other indoor air quality problems such as excessive condensation during winter.

An HRV will cost about $1,500 to $2,500 (material and labour). There is also an operating cost for electricity for the HRV’s fans as well as an increase in heating and cooling costs due to greater ventilation of the home.

Contact your REALTOR at Coldwell Banker Vantage Realty for more tips and advice on what you can do if you have concerns that you have Radon in your home.

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