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I have an existing HVAC system on a 2 story, 2500sq ft house + finished basement in Pennsylvania. We have radon in the basement, which fluctuates between 1 and 3.5. It's controlled by a mitigation system, but we'd like to reduce it further. An ERV was suggested, which would also provide the benefit of passing more fresh air through the house.

An HVAC tech came by and said that we could hook the ERV ventilation into the existing HVAC system, and the ERV would drive fresh air through the house. However, he later realized that the 150 max CFM wouldn't be sufficient to drive air through our HVAC system. He suggested one of the follow solutions:

  1. Hook ERV into basement HVAC and leave HVAC fan running all the time. The HVAC would then drive the fresh air that the ERV pumps in and out of the system.
  2. Keep the ERV as its own isolated system in the basement. This would circulate the basement air, which is the air w/ most radon. However, we'd lose the benefit of fresh air in our whole house.

Can someone confirm that home ERVs do need to hook into existing HVAC systems to drive air flow through a house? And secondly, any recommendations on how you'd proceed in my situation?

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  • Recommendations are a no no. – JACK Jan 15 at 14:47
  • Recommendations for the ERV itself or recommendations on how to proceed with my issues? – Adam Hughes Jan 15 at 14:50
  • For the ERV itelf. – JACK Jan 15 at 15:38
  • k fixed it thanks – Adam Hughes Jan 15 at 16:01
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As far as an ERV and if it is needed depends on how tight your house is. How much do you need? This again depends on your home. A newer home built in the last 20 years with a central heating system they can replace the make up air intake save a little of the outgoing heat pull the excess humidity out and improve over all air quality.

To really do this they need to be on more than the furnace or ac usually runs and on all the time is the normal recommendation. Without the radon concerns I recommend when occupied, with radon concerns 100% run. A 150 scfm is a lot that is more than many bathroom fans running all the time this will increase your energy cost for both heat and cooling (the erv is not even close to 100% efficient)

this is one area I tell people don’t be over sold. Yes they recover energy but what size make up air do you have on your house now?

It’s easy to measure the duct size vs the wind speed. A simple handheld anemometer can provide the existing flow.

If you don’t have make up air now do you even need 150?

If you don’t have makeup air now and many homes do not going hog wild will increase your utility bills and a smaller system will probably improve the air quality. The air handler is moving the air through the house not the erv.

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  • Thanks - so what if I just had the erv and hvac system fans run in a synchronized manner, say for 20 minutes every 2 hours. Do you think that would be ample time to refresh the air? – Adam Hughes Jan 15 at 15:39
  • I would want the erv running when the system is running the air is not fully conditioned it will be colder in the winter or warmer in the summer so mixing it with conditioned air is the best way to distribute the fresh air. If your hvac guy doesn’t understand this, you might want to look around to someone that is more versed with HRV or ERV systems my last home I had the make up air on all the time and an electrostatic filter, my daughter would come stay with us during field burning because her daughter has severe asthma and the air quality in that house prevented problems a bit larger 2 story – Ed Beal Jan 15 at 15:52
  • Yes cycling the system will help but if not running the fan more than 20 minutes an hour the ERV is really an expensive idea and won’t change things much. – Ed Beal Jan 15 at 15:55

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