Our slightly radioactive cottage
Last updated
Last updated
Radon is a radioactive gas that comes from the ground. You can’t see or smell it. It can build up indoors, and long-term exposure increases the risk of lung cancer — in Ireland, it’s the second leading cause of lung cancer after smoking. Ireland’s reference level for homes is 200 Bq/m³, measured over time. The EPA recommends a three-month test with detectors in the living room and main bedroom. I started measuring because I wanted to know what happened between those longer tests, as in general you only get the results at the end.
The first few days were all over the place. The living-room monitor could drop below 100 Bq/m³ and later climb several hundred. One timestamped export recorded 1,041 Bq/m³ on March 1st. I’d later remember the worst peaks as being in the 700s; the export is the better record, so that’s what the chart shows.
We work from home, so the living room is more than somewhere we sit for an hour in the evening. I later put a second monitor in the bedroom and saw early peaks there too, around 300–400 Bq/m³.
Opening the windows made a visible difference. On February 28th, the living-room reading was 689 Bq/m³ at 10:14. I opened the windows for roughly twenty minutes, starting around 10:20am. By 11:54, the monitor read 222.
That was reassuring. We usually do a ventilation flush every morning for 10–15 minutes anyway (just to get that fresh air in), but it’s not great to rely only on that, as on freezing cold and windy days opening doors and windows for 20 minutes is not that enticing. A cracked window almost always helped; but at other times the number rose anyway.
I tried to find the source. I discovered that our pellet boiler had a disconnected air-intake hose and reconnected it. Readings later changed, but with the weather, heating and ventilation changing too, it’s difficult to attribute lower numbers to this change.
The monitor also records atmospheric pressure. Two March mornings made a tempting story. On March 25th, pressure rose while radon generally fell. On March 29th, pressure fell while radon generally rose, before the radon reading dropped again near the end.
Across those short runs, the correlation between the levels was −0.64 on 25 March and −0.71 on 29 March. That sounds persuasive until I compare each ten-minute change with the next: those correlations were −0.03 and +0.05. The broad curves moved together in opposite directions, but one pressure change didn’t reliably predict the next radon change. I hadn’t logged every door opening, window setting, or heating cycle either. Pressure might matter; this data cannot tell me how much.
This is where the problem stops being an interesting graph. Finding a contractor who can assess this house and carry out the right work has been harder than I expected. The EPA keeps a list of registered radon remediation contractors, but having a list is only the start of getting a site visit, a proposal, and a follow-up test.
It also seems far less understood than it should be. In an EPA survey published in June 2026, awareness of radon had fallen from 82% in 2020 to 71% in 2025. More than half of respondents didn’t know about its link to lung cancer. I didn’t know enough about it myself until we got someone to do a survey of our well water and he mentioned that radon might be a problem here — thanks for the heads-up, Bruno!
There are possible fixes, including ventilation and a radon sump, but the right choice depends on the building and the measured level. The EPA says positive input ventilation is usually suitable only for relatively airtight homes below 700 Bq/m³; it says an active sump typically reduces levels by about 90%, though results vary.
I now have exports spanning 22 July to 20 October for both rooms. There’s a shared recording gap of nearly eight days in August, which I’ve left blank on the chart — summer levels were so low I didn’t bother to sync it. The chart shows daily averages for the full period.
On days with at least 100 readings, the median daily average in the living room was 66 Bq/m³ in July and 244 Bq/m³ in October. In the bedroom, it went from 83 Bq/m³ to 172 Bq/m³. August and September sit between them, though the rooms don’t move in perfect step. The bedroom’s monthly figure was higher than the living room’s in August and September; the living room was higher in October — around the time we started to put on the fire.
This supports what I suspected: the readings were generally lower in summer and grew as autumn arrived. I’ve also noticed that on really windy and dry days levels are generally lower. I’m guessing maybe wind coming through the air bricks under the floorboard gets the radon out.
I didn’t keep a complete log of windows, heating, wind, or any work we’ve done on the house — I’m not a maniac.
Now I’m looking for someone who can install an active radon sump, and if I can’t get anyone to do it, I might just do it myself.