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HRV's integrated into furnace ductwork efficiency

  • 7 Jun 2024 12:51 PM
    Quote
    Message # 13367390
    Chelsah Thomas

    Hi everyone, 

    I have a question and you're the best resource I know!

    HRV's that are integrated into the ductwork of the furnace (passive) technically should have a lower efficiency for the system set up rather than a dedicated HRV with low volume ductowrk. However, when I compare the two approaches, the energy consumption remains unchanged. The only item I'm changing is that one model uses low volume ductowrk, and the other uses forced air heating ductwork as the distribution/circulation type.

    I have went through technical procedures and the Hot2000 modelling documents but don't have an answer. 

    Example: Builder is installing an HRV (Lifebreath RNC205) integrated into the gas furnace ductwork. The HRV has a -25 degree celcius rating of course. How should we model this approach to account for the lowered efficiency of this set up? 

    Thanks!
  • 10 Jun 2024 5:50 PM
    Quote
    Reply # 13368458 on 13367390
    Graham Knights

    The efficiency isn't dependent on the interior configuration of the ductwork, it would still be drawing in fresh unconditioned air, and exhausting stale inside air to the exterior; only the location of the interior ducts would have changed.  Static pressure could potentially be lower due to less ductwork, so technically efficiency might marginally improve - at least for the energy consumption of the fans.  Regardless, the HRV would operate the same regardless of the interior duct configuration.

    Depending on your location, the method of installing the HRV with both the supply and exhuast attached to the furnace ductwork is not compliant under the BC Building Code, but may be compliant in other areas (TECA does not recommend this configuration).  Section 9.32.3.4 covers ventilation systems, but installation method is not really a concern for EA's :)
  • 11 Jun 2024 6:35 AM
    Quote
    Reply # 13368652 on 13367390
    Anonymous
    Chelsah Thomas wrote:

    Hi everyone, 

    I have a question and you're the best resource I know!

    HRV's that are integrated into the ductwork of the furnace (passive) technically should have a lower efficiency for the system set up rather than a dedicated HRV with low volume ductowrk. However, when I compare the two approaches, the energy consumption remains unchanged. The only item I'm changing is that one model uses low volume ductowrk, and the other uses forced air heating ductwork as the distribution/circulation type.

    I have went through technical procedures and the Hot2000 modelling documents but don't have an answer. 

    Example: Builder is installing an HRV (Lifebreath RNC205) integrated into the gas furnace ductwork. The HRV has a -25 degree celcius rating of course. How should we model this approach to account for the lowered efficiency of this set up? 

    Thanks!


    Wouldn't the lower system efficiency come from the fact that the furnace fan has to run continuously?    
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