ERV integrated with H-AC or independent


I am wondering what most people are doing - tieing ERV/HRVs into the H/AC ducting or using dedicated ducting. It seems to me that with such small air flows, one can never properly balance where the fresh air goes - to bedrooms and where the exhaust comes from - kitchen and bath, when the ERV/HRV is tied into the ducting network of an H/AC unit. But... if using an indpendent ducting network, what (multistory) house has enough space to run two ducting systems unless one uses Zehnders with their 2" ducting distribtuion system.  In looking at the installation instructions, it seems that most manufactuers assume the ERV/HRV will be tied into the H/AC ducting network either on the supply or return side. Here in CA, we have very strict requirements for H/AC ducting not to leak more than 5%, yet if an ERV/HRV is spliced into the network, it introduces many more opportunities for leakage. Furthermore, if the ERV/HRV is a "Return-Return" tied system, the H/AC fan must operate, which has been shown to kill the energy efficiency of the system as those motors are huge compared to the built in ones for the ERV/HRVs. So, it seems wierd to me that ERV/HRVs are ever tied into the H/AC ducting for distribution, but yet that seems like the only realistic (reasonable) option.  

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  • Sean says there are 100 ways - He is short over 8000 ways.   Keep your eye on what you want.   What is the goal? top 6 of  good air health,comfort,safety / Chemical Pollutants/ Carbon Dioxide/ Temperature / RH% Relative Humidity / Carbon Monoxide / dust - Particle - allergens. /  You could have a spot with high RMF / or iron  or something else

    Then benchmark what level is needed for you?  I use EPA, OSHA,, Leed, ASHRAE, WHO, IAQA

    how are you going to test your building?  how?  When?  Why? what level?   +- 10% 50%

    Then I have tested over 5000 buildings,  so I match the building to the need.  Same SF building can need 950 CFM outside air to 100 CFM outside air.   Keep learning - Test in Test out

    Keep in mind most ERV's are put in by the HVAC trade.  So will be tied in with air handler will be done.   If you are using cool beam, super tight building,  very high eer cooling system then a dedicated dehumidifier ERV/HRV system may be used.


  • There are a 100 ways to skin a cat... I personally like keeping them seprate & as simple as possible - supplies in bedrooms, with 1 return pulled from area far away like say a basement, living room, 2nd floor hallway (damper between upstairs & downstairs so you can choose location)

    You may also look into VHAC - that is where the ventilation supplies the conditioned air to the bedrooms only & they use a mini split to condition other rooms & where exhaust is pulled (Washington State thing as memory serves me)

    As for tied directly into unit - you pop the cover off & seal the connection between the units - in most cases / bulk I have seen they pull air from elsewhere (exhaust) & only the intake is what goes back into the return. You are still getting air moving through the system even with the HVAC fan off though many do run the fan at set intervals

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