Openings and joints
in a foundation that may allow radon to enter can be patched
or caulked. For sealing cracks in poured concrete walls, we
recommend polyurethane foam injection. Polyurethane remains
flexible for years, as the house settles and concrete continuously
moves. Caulking the surface only is inadequate - the gap fills
up with radon gas which then easily by-passes the caulk through
concrete. Surface caulking will soon detach as moisture degrades
the concrete surface and it cannot withstand hydrostatic pressure.
Open sumps can be fitted with an airtight cover Floor drains
can have special traps installed that allow water to drain,
but prevent radon from entering the basement. Exposed soil
in crawlspaces can be covered by a barrier with sealed edges
and joints.
One problem that still remains is the porosity of the concrete
itself. Products like Radonseal, Radonloc and
Vseal address this by penetrating the microscopic pores
in concrete and then solidifying to create a seal.
The pores constitute 12 to 18% of the concrete by volume.
Their diameter is much smaller than a human hair but much
larger than radon atoms or water molecules. They let in
radon gas, water vapor, liquid water, and other gases.
2. Reducing the 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. To reduce negative pressure in your
home, open a nearby window to provide outdoor air when using
a fireplace or wood stove. When not in use, make sure the
chimney damper is shut. Where possible, also open a nearby
window when you operate an exhaust fan vented to the outdoors
such as the kitchen fan, bathroom fan, clothes dryer or
central vacuum system.
3. Pressurize the House/Building
According to the California Energy Commission "The
preferred method of ventilation is to push air into the
house.. the supply fan approach. This approach is preferred
because it directly controls the source of ventilation air,
and because it will not depressurize the house which could
cause backdrafting of fireplaces and/or combustion appliances.”
DOAS (Dedicated Outdoor Air Systems) are intimidating, often
requiring considerable expertise in installation and setup,
and periodic maintenance. Because simple changes require
an engineer or maintenance person, system complexity has
traditionally prevented the use in residential buildings
and locked local heating and air conditioning contractors
out of this market.
To operate a DOAS year round you need to know outdoor absolute
humidity, i.e.., how much water vapor is in the outdoor
air. Other factors, temperature, humidity may be considered.
The system then needs to know what the occupant accepts
for his or her comfort, then how to process the outdoor
air. There now are inexpensive and easily installed systems
available.
In Conway, Arkansas, Smartvent,
Inc., makes a supply fan ventilator called HI-IQ because
it is an intelligent ventilation system.
Another ventilation approach would be an HRV (Heat Recovery
Ventilator) which exchanges some heat between incoming and
outgoing air. There are drawbacks to the HRV, it can only
operate in the winter, requires maintenance, and since incoming/outgoing
air flows must be evenly balanced and it has no effect on
carbon monoxide backdrafting. But it will reduce radon levels
and may be more economical in the long run due to energy
savings compared to a DOAS.
4. Depressurizing the soil around the foundation
Active soil depressurization has been found to be the most
effective and reliable radon reduction technique in existing
homes. 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 which 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.
With this method, the main drawbacks are installation cost
and an ongoing energy penalty to run the fan and replace lost
heat. Depending on the base under the slab, more than one
sump pit may be required to vent the radon.
5. Activated Charcoal Air Filters
Some companies claim that their activated charcoal air
filters remove Radon. How effective the filters are would
need to be verified.
A comprehensive guide entitled “ Radon: A Guide for Canadian
Home Owners” can be download from this site or CMHC or
Health Canada.
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