Hi op. Following up on your concerns. You note any changes with the cooler weather and now running heat ?

Radon fans are not that strong. If your HVAC is that strong, I wonder if your radon fan do the job properly (I.e., your negative pressure from HVAC may overwhelm radon fan). Just a thought.

We used JK Radon to install our system. We went from 6 down to 1.4 and sometimes lower.

Anonymous wrote:OP again - thank you for this idea. I started the good weather experiment and first just turned the A/C to the temp outside so it wasn't in cooling mode - radon went from 16 to 10 with all windows closed within 6 hours. We had gotten it down to 14 with all windows/doors open all day, but it was creeping back up at night. This morning I'm turning the whole system off to continue monitoring. Wow....

Yup, causing negative pressure as mentioned.

OP again, thank you for the advice. The old system was a traditional variable system from Carrier, about 20 years old, and we just ran the fan on high. This new system was indeed running at what felt like a much lower capacity than what we had before - so our HVAC contractor set the airflow higher and it overrides some of the efficiency settings in order to provide more airflow upstairs. I wonder if that could be contributing to the radon situation. I read somewhere else that a heat pump that is upsized for the environment it is in can backfire and not work well, but I just don't understand enough about it to opine on it. We will definitely be remediating the radon along with continuing to try to assess what's happening. This was very helpful advice to think about. My sense is that the Heat pump installations are much more complicated than the older models.

So this is a new one for this HVAC contractor but as others have suggested its certainly plausible that a system could create a negative pressure environment in the basement that could increase measured radon. That being said it would have to be a perfect storm of a very tight home, poor duct design, and an oversized and/or misconfigured system.

What doesn't make sense to me is that the old system didn't cause this issue. The new Infinity VS system should be running longer but at a lower capacity and reduced airflow compared to the old system. Theoretically it should be creating less negative pressure in the basement compared to the old system; everything being equal. That fact this is happening and that they felt the need to add additional return air from the basement leads me to suspect the system is overly upsized. Reconfiguring the system's airflow settings should correct the situation. Whether the existing duct system will adequately heat and cool could be a whole other issue.

Personally when this gets sorted out I would spent the money to get a remediation system installed either way.

OP...you can bypass the garabage heat pump function (running if outside temps are >35) and run gas heat 100%. We have the trane hybrid system and we run it gas 100%. The bypass can be selected to use "emer heat" from the thermostat and this never kicks in the heat pump

Impossible. It's naturally occurring.

OP again - thank you for this idea. I started the good weather experiment and first just turned the A/C to the temp outside so it wasn't in cooling mode - radon went from 16 to 10 with all windows closed within 6 hours. We had gotten it down to 14 with all windows/doors open all day, but it was creeping back up at night. This morning I'm turning the whole system off to continue monitoring. Wow....

Make sure any holes in the concrete are sealed. We did waterproofing/sump pump and ours went higher as the slab was altered and open with the sump pump. We sealed the sump pump and did radon mitigation. It immediately went down.

Website is terrible but we used: https://radonrepair.com/about-us-radon-mitigation-service/

Anonymous wrote:

Anonymous wrote:Modern houses that are airtight tend to cause a host of more health problems, via radon radiation, mold, negative air pressures affecting both and your health, etc.

Opening windows often is a good thing. Especially if you have granite counters, certain tiles, and basements.

Current codes that local jurisdictions are not using yet require fresh air intake. Homes with proper fresh air intake are fine. Opening windows is fine as well. Current codes require passive radon mitigation so that shouldn’t be a problem for anything built in the past two decades. Basements should have a barrier between slab and soil negating these negative impacts. It is rare for radon to exist in granite countertops. Stop spreading fake news.

Learn more sport. Things exist that you apparently don't know about.

Op again thanks for the tips. Unfortunately Tim Hughes is out on medical leave. Can anyone recommend an HVAC engineer who would be able to evaluate the system? Thanks in advance

Anonymous wrote:Modern houses that are airtight tend to cause a host of more health problems, via radon radiation, mold, negative air pressures affecting both and your health, etc.

Opening windows often is a good thing. Especially if you have granite counters, certain tiles, and basements.

Current codes that local jurisdictions are not using yet require fresh air intake. Homes with proper fresh air intake are fine. Opening windows is fine as well. Current codes require passive radon mitigation so that shouldn’t be a problem for anything built in the past two decades. Basements should have a barrier between slab and soil negating these negative impacts. It is rare for radon to exist in granite countertops. Stop spreading fake news.