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Fresh Air at low Humidity with no ERV - radon issue

Posted by kyzer (My Page) on
Thu, Sep 30, 10 at 15:08

My home was built in 2007 and has a 1500sqft unfinished walkout basement. We found radon and recently installed an ASD system to lower the levels from beneath the slab. I would like to add ventilation, but am concerned about the added humidity and ERV would add.

I have a 2ton HVAC installed and running and the current humidity hovers around 52%. The basement has always been dry and does not smell. Radon levels are in low 3s.

I just want fresh air at low humidity so I was thinking something like this Honeywell DR90vpiaq Dehumidifier with FRESH AIR INTAKE would be a good option to tie into the current HVAC return? The literature says it ventilates and has MERV 11 filters etc.

I also thought about adding a point source dehumidifier and
a simple air exchanger like this from fantech AEV1000.

Anyone else already solve the issue of fresh air at low humudity?

Follow-Up Postings:

RE: Fresh Air at low Humidity with no ERV - radon issue

I noticed I may not have been clear. I am only interested in basement ventilation. The 2ton HVAC is the basement system. Upstairs levels for radon, humidity, etc were lower. I have a 3.5 ton HVAC for upstairs supporting around 2000sqft.


RE: Fresh Air at low Humidity with no ERV - radon issue

The installers of the radon abatement system should have sealed the entire basement floor to wall joints, any piping that penetrates the concrete, and a sump pump cavity. That should have been part of the complete ASD package.

Is there a drain in the basement floor? There should be one for the condensate from the 2 ton AC unit. The dehumidifier will need that drain as those units often produce more condensate than the AC unit.

The second unit you mentioned would further mitigate the radon. But a reading, taken correctly, in the 3's after the ASD has been installed is a bit high.

Within the prescribed limits, but a good ASD system that is properly installed should lower the readings to less than 3.

RE: Fresh Air at low Humidity with no ERV - radon issue

Thanks handymac.

So do you think the Honeywell unit will also ventilate well enough to further mitigate with the added benefit of dehumidification. Understanding that exhaust will also be required, my HVAC contractor is saying he can bring in up to 200CFM on the fresh air intake of the Honeywell unit without overlaoding my HVAC. In looking at AEV/ERV sizing info most units are less than that amount of CFM for 1500 sqft and 8 ft ceilings. I don't know how many Air Changes per minute/hour 200CFM would be, but am I missing anything with this logic?

Seems this Honeywell unit will be bringing in fresh air same as ERV when it is running. I don't think I need to ventilate constantly given I have the ASD handling the bulk of things.

I agree the ASD should have gotten things lower. 3.0 was the lowest EPA reading in the basement so far. My wall studs are in place so he sealed the floor perimeter as best he could with foam insulation style caulking. There are two suction points and a big fan. After install, I had the system checked out by another mitigator and he said it was pretty much done by the book and was scratching his head also. I will probably go back over things with polyurethane caulk before the sheet rock goes up. Both mitigators said finishing the poured basement walls and adding flooring should also further mitigate things.

I don't have a sump. I plan to pump out the condensate in the same manner as my current HVAC does up into the ceiling and out the wall to a gutter drain.

I welcome comments..

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