Radon

[Carnak]

Yes, pressure increases as the square of the airflow but your conclusion is reversed. You get more airflow at low pressures than you would expect if the relationship was linear.

BTW, that's a thread from 2007 (!) that evenflow dug up, with X and Carnak fighting. Smells like a troll. If he wants to repost in a new thread I'll be happy to "pontificate"

Lol, even sounds like it is aimed at me.

There was another user registered around the same time period, one was called 'informedhomeowner' or something to that effect, that seemed to fixate on me.

2 posts in 5 years sounds like someone just remembered a password for an alter ego

[pmeunier]

We must have a fundamental misunderstanding of the airflow vs. pressure relationship. If you have a hole in the wall (or say, a 10-foot duct 4 inches diameter) and outdoor pressure is just the same as indoor pressure, you would expect no airflow would you not? If you had negative 0.1 inch w.c. indoors, you would expect some airflow I am sure.

Of course (ignoring any side winds or stack effects). However I don't know how many Pascals there are in 0.1" w.c.; I assumed that the poster was going to connect the duct to the furnace return and get somewhere between 0.1-0.2 w.c., and I don't understand why you think that the airflow would be negligible under those conditions. Whether it's enough or not for his house and # of occupants, and what is the resulting pressure in the house and if that's enough for radon mitigation are another matter.

Not sure of the point of view where you get more airflow with less pressure difference to drive it. I'm sure you have a correct thought, just not understanding what yours is.

Understanding these laws of physics is fundamental to how (and whether) certain products work. The thread may be old, but the laws of physics thankfully have not changed <g>.

Best wishes -- Pstu

Pstu, indeed you get more airflow with more pressure. The question is how much. This depends, amongst other things, on whether the flow is laminar or turbulent. For turbulent airflow, the pressure needed to get a certain airflow increases as the square of the desired airflow. So, as you increase pressure, the airflow does not increase in proportion -- you get less airflow than if the relationship was linear. It follows that if you decrease pressure, the airflow does not decrease in proportion either. You get more airflow than if the relationship was linear. It may be more obvious graphically. Draw a parabola y=square(x), where x is the airflow and y is the pressure. Pick a point on the curve representing a given airflow and pressure, then draw a straight line y=x from that point to coordinates 0,0. If you lower the air pressure while following the parabola the airflow is greater than if you follow the straight line. Hence my statement, you get more airflow at low air pressures than you would expect if the relationship was linear. For the sake of this argument I'm ignoring the non-turbulent airflow region.
I guess my point is, don't underestimate how much airflow 0.1" w.c. can generate...

Regards

[Carnak]

1" WC=249 pascals

[pmeunier]

1" WC=249 pascals

Thanks Carnak. The misunderstanding is from my ignorance then, if pstu mentioned just a few pascals then that was not the situation I was thinking about. Let's drop it since the poster is not clarifying the question.

[Drippy]

There is an EPA booklet titled,"Consumer's Guide to Radon Reduction", How to reduce radon levels in your home. Air and Radiation 6604J, August 1992 402-K92-003.

What I gather from that is for an existing house is to seal all cracks, seal the sump and install a low cfm exhaust fan from that. After that, an air exchanger can be installed to dilute the contaminant level. You could also pressurize the lower level to keep the contaminant at bay by bringing in more air than exhausting. We have done that part successfully with ERVs many times.

The radon test should be done a couple times to get a good average reading. It will vary by season and humidity content of the ground.

[evenflow]

Whatever a troll is maybe so, do they make those troll 6' 220 lbs. I dont know. Anyway If I offended some one with my post sorry. I am just checking out stuff for my education but I do see some redundancy in this thread and just put my 2 cents in. You wanna bust my balls go ahead it's all good. Oh I don't think I have replied to many posts. Have a good Labor Day.