The headline above does not mean that I am an expert on radon. Rather, the idea is to present some interesting new facts while also discussing strange misconceptions about radon.
I bought a house three years ago that lacked a radon report. I found it unsettling, so a clause was added to the contract to share any potential decontamination costs. But the realtor and lawyer on the other side were savvy enough that the time frame was too short for a serious radon measurement to be conducted. The house is a split-level. Concrete slab. FTX ventilation.
It turned out to be 2500Bq/m3 on the lower floor on a good day. Annoying, but I managed to conduct my own decontamination with a radon extractor that cost one-sixth of what the decontamination companies quoted. Since I wanted to keep track, I also bought an expensive radon monitor of my own.
It was around then that questions began to arise about the measurements themselves. After some measurements, I noticed that the values followed outdoor temperature curves with some delay of course.
+10C gives 40 Bq/m3
0C gives 70Bq/m3
-10C gives 100Bq/m3
-20C gives 150Bq/m3
Why is that? I also notice that the values rise with a lot of rain, but I have no statistics on it. Does anyone have a good theoretical explanation?
I bought a house three years ago that lacked a radon report. I found it unsettling, so a clause was added to the contract to share any potential decontamination costs. But the realtor and lawyer on the other side were savvy enough that the time frame was too short for a serious radon measurement to be conducted. The house is a split-level. Concrete slab. FTX ventilation.
It turned out to be 2500Bq/m3 on the lower floor on a good day. Annoying, but I managed to conduct my own decontamination with a radon extractor that cost one-sixth of what the decontamination companies quoted. Since I wanted to keep track, I also bought an expensive radon monitor of my own.
It was around then that questions began to arise about the measurements themselves. After some measurements, I noticed that the values followed outdoor temperature curves with some delay of course.
+10C gives 40 Bq/m3
0C gives 70Bq/m3
-10C gives 100Bq/m3
-20C gives 150Bq/m3
Why is that? I also notice that the values rise with a lot of rain, but I have no statistics on it. Does anyone have a good theoretical explanation?
One guess is that low outdoor temperature creates a greater negative pressure in the basement (chimney effect) and thereby larger leakage of ground air into the house through cracks and leaks in the basement walls/slab. The negative pressure of the radon fan is partially counteracted by the chimney effect.
/Ingenjören
/Ingenjören
yes, the low outdoor temperature creates greater negative pressure in the basement which draws in radon from the ground. Additionally, ventilation is reduced when it is cold outside, meaning more radon remains in the indoor air.
In principle, what the engineer writes is that the lower temperature creates a greater "chimney effect" and thus more radon-rich air is drawn into the dwelling. However, there are additional factors at play, so one cannot directly say that the relationship between outside temperature and radon gas levels in the home is linear. For example, the "system" is influenced by the ground temperature at various layers, and the relationship there is relatively complex, requiring essentially a model for each home and its foundation + surrounding ground situation. Furthermore, it must be taken into account that most instruments are designed such that what they display has a lag of about 3-4 days. This is because the instruments measure alpha particles that arise from the decay of indiffusing radon gas in an ionization chamber. (thus the equilibrium for WL arises about 3-4 days after the equilibrium for radon gas levels)