We recently had a radon mitigation system installed in our basement.
The contractor also installed a passive make-up air vent (a pipe
connected to the outside to let fresh air in) in the basement to
prevent backdrafting of furnace.
We have a forced air heating system. The furnace is in the basement and
the basement IS heated. But the thermostat is on the first floor.
Should I be concerned about water pipes (in the basement) getting
freezed by the cold make-up air in the winter? We live in New England.
It can get pretty cold in the winter.
If yes, how should I handle it? I don't want to close the make-up vent
because I did notice some backdrafting when it's closed.
You don't want to close off the make-up air. Not if you like living.
BTW you sound like a good candidate for a CO detector if you don't have one.
I highly recommend one.
I am not sure of what is going on in your systems. My guess is you may
do well to enclose the furnace in its own room and feed the make up air
directly to it, or replace it with a new high efficiency unit that will have
a sealed system and you can connect the make-up air intake directly to it.
An old house should not need make up air, a new extremely tight house
maybe yes. A blower door test is needed to find out air exchanges per
hour. Does it back draft when dryer and exuast fans are on. This could
be a chimney issue, wind or cold flue, or blockage as in debris or dead
bird, I would look into it more.
i don't know what would happen if you turned the radon fan off for
there sure is lots to read at
and test kits at
Thanks guys for your reply.
I don't want to turn off the Radon mitigation system for the winter
because the Radon level was quite high without it.
I don't want to close the make-up air vent for safety reason as Joseph
said. As I mentioned, I did notice backdrafting of furnance when the
make-up air was shut off.
I want to know if anybody has experienced or heard of pipes in a HEATED
basement got frozen because of make-up air. If yes, any relatively
simple way to fix the problem.
I got some useful suggestions. More are appreciated.
We put a second backup thermostat in our basement for just this reason.
We wired it up so that if the basement drops below 40 or so the furnace
turns on (regardless of how hot it might get upstairs). Not really
ideal, but a few times on really cold nights it has tripped. If I hear
the furnace turn on, and can go adjust the heat vents to put more heat
into the basement. Really I'd like to have some sort of buzzer or
indicator light that alerts me to the fact that the basement is getting
I didn't have handy a thermostat that went that low, actually, so I
just installed a mercury-switch type one at an angle, and subtract 20
from the scale. Tricky to get the angle right, but seems to work.
In decending order of cost-effectiveness:
Heat tape on the pipes.
Direct external air supply for the air-using appliances
that AREN'T radon mitigation.
A heat-exchanger for the radon system, if it's supply
and exhaust are both ducted.
I have seen pipes freeze in a heated first floor. It really depends on
a number of factors and it could happen in a basement under the right or
Assuming the make-up air outlet is not near the pipes, you should be
safe, but get something cold enough and it will freeze. I suggest you keep
a thermometer down there and check it from time to time when it is really
cold out. Move it around to find the cold spots and how cold it is around
the pipes. You can even buy cheap digital models that will hold the lowest
and highest temperature until reset. You should get a good idea about the
conditions you will need to worry about. You also can get a warning device
that will alert you if it gets close to freezing.
Here's what I did for the same thing. My boiler was in it's own little
room, when the makeup air was installed with the new boiler I had them
create a duct for it to follow the basement wall to about 6" from the
floor. This way the heat the boiler gives off does not go out the vent
during the off cycle. Once the cold air from outside equalizes the
bottom foot or so of the boiler room it stops coming in until needed
for the combustion process.
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