I had the radon checked in the basement 1 yr ago. It measured 6 pc/L. I
paid to have a sub slab depressurization system put in. It maintains 2.5
inches of water vacuum. I also installed an electronic continuous radon
monitor. In the summer when the swamp cooler runs the radon level drops
to almost zero. In the winter the furnace runs and the levels go up to
16 pc/L. The sub slab system is useless as the soil is bentonite clay,
it has zero porosity. The contractor guaranteed results but it is like
I want to pressurize the basement to stop the radon. I'm thinking of
forcing air from the first floor into a semi sealed basement through a
floor register via a duct fan. Here's my questions:
1. Can I use a radon fan to pressurize the basement?
2. If so, will it operate ok upside down?
3. Will excessive over pressurization cause problems with the furnace
and hot water heater (both natural gas) in the basement?
4. How many inches of overpressurization is ok for the basement? I have
a filter manometer to measure this with.
5. Is there a better way to do this?
6. What fan would be best?
I want the system to run quietly for years w/o maintenance.
I seriously doubt you will ever "presssurize" a basement.
Besides the porous building construction, there are those
pesky gas appliances. Assuming the furnace and heater are
natural draft, any excess air you manage to force into the
basement will simply bypass up the draft diverter to the
The swamp cooler obviously pressurized the basement. The resistance of
the heater flues will cause a pressure in the basement. I'm worried
about too much air flow causing havoc with the pilots.
I would guess that the furnace is
sucking air (radon) from the cracks in the
floor, etc when the gas is actually
burning, i.e combustion. Maybe you could
add a fresh air vent to the furnace area
to "allow" it to suck in outside air and
not cause negative pressure in the
basement. Just a guess. But, I would lean
on the contractor as hard a possible.
Mr. Tool wrote:
The fresh air intake would definitely help. However, it is a 40+ yr old
cast iron boiler that does not have an air intake port. It sucks air up
through the whole bottom of the furnace so I would be letting lots of
cold air into the basement. Thanks,
The EPA publication:
"House/room pressurization uses a fan to blow air into the basement or
living area from either upstairs or outdoors. It attempts to create
enough pressure at the lowest level indoors (in a basement for example)
to prevent radon from entering into the house. The effectiveness of this
technique is limited by house construction, climate, other appliances in
the house, and occupant lifestyle. In order to maintain enough pressure
to keep radon out, the doors and windows at the lowest level must not be
left opened, except for normal entry and exit. This approach generally
results in more outdoor air being introduced into the home, which can
cause moisture intrusion and energy penalties. Consequently, this
technique should only be considered after the other, more-common
techniques have not sufficiently reduced radon."
Radon fans are designed to work for years w/o worry. I want to know if
using one to pump air from the first floor into the basement is the best
solution. My concerns are that the radon fan is made to suck under load
and I want it to blow under very little load. This changes the torque
loading on the motor and I'd like to know if that is worth doing. A
radon fan also fits nicely into pvc tubing. To get away from putting a
loop in the line I'd line to mount the fan upside down from its normal
operating position. Does anyone know of similarly housed fans for this
purpose? There is very little information on this on the internet.
The swamp cooler pressurizes the basement to about 0.75 inches of water
and I believe that is stopping the radon from entering. The clay soil
and the contractor I believe has ruled out sub surface slab suction. I
don't want anymore tubes stuck into my finished basement. I have seen
the pressurization work with the swamp cooler. I simply want to approach
an optimum solution with regard to cost, noise and space used up.
I appreciate all the help and suggestions and hope that kwr isn't
embarrassed by learning something useful from this discussion. Thanks to
Act and think in peace and love,
you will certainlt bother basement chimney devices with your plan.
this also requires climate info, see:
or search radon at:
Mr. Tool wrote:
this website says their fans are 100% speed controllable.
perhaps if your monitoring system has an output; you could vary the
speed of the fan to match automatically. but if it's just a seasonal
radon variation, perhaps add a variable speed control if permitted in
your building's code requirements. mfg link at:
and radon at:
Mr. Tool wrote:
If the boiler is 40+ years old, I'd look into whether new ones are
available that will pull combustion air from outside. All the new
high efficiancy gas fired forced air ones that I've seen do this.
Would think it probable that you could get this in a boiler as well.
That would directly solve the problem of the furnace drawing basement
air and with a new furnace, likely save you some energy cost as well.
I would think one risk with pressurizing is you might wind up blowing
radon concentration from the basement into the living space.
Thank you! Great information from you and everyone!
I will bring in outside air for my furnace. It is in a large closet with
vents. I'll close off the vents and make sure good outside air flow goes
to the furnace. The furnace air will be isolated from the basement air.
I'll pressurize the basement with the adjustable fan and monitor the levels.
Thanks everyone for all the great help!
Now I've got to chop through the brick facing to get outside air. Ugh!
make sure there are no major leaks in the RETURN ducts in the basement
which would lower the pressure in the basement when the furnace runs...
also I have added a fresh air intake duct ( a small dryer type duct)
to feed fresh outside air to my return ducts. This pull in fresh
outside air when the furnace runs and tends to pressurize the entire
house a little...
this air will eventually feed the combustion also
you are on the right track in my opinion, try to raise the pressure a
bit in the house especially the basment...also seal all cracks at the
upper levels of the house where the warm air leaks out...
I too think he is on theright track.
provide a easy source of combustion air for vented appliances.
seal all floor and other cracks to minmize radon infiltration INCLUDING
the top of the sill plate where it meets the foundation wall.
If all else fails a friend added a small comuter muffin fan and a small
air intake on opposing sides of the basement to ventilate what radon
does seep in
some around here report GREAT reductions by tying a interior french
drain into the radon system so the exhaust fan pulls from all around
the basement. A great option if you have water troubles
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