HRV/ERVs and Energy Star

HRV with cover removed

I was asked recently about HRV/ERVs and Energy Star.

  1. Energy Star V3 does not require the use of HRVs or ERVs, but it does require that the ventilation system must be designed and installed to meet ASHRAE 62.2-2010.
  2.  There is no Energy Star program for HRVs or ERVs in the U.S.
  3. There is an Energy Star program for HRVs and ERVs in Canada that was developed specifically for Canada.  This program has operated for approximately 2 years using tier 1 specifications.  Tier 2 specifications went into effect in July of this year.  Note that these are Canadian Tier designations.
  4. US EPA did not replicate the Canadian Energy Star program because it was not clear that the Canadian specifications were in the best interests of U.S. homeowners.  The main issue being that there is no energy savings value for the -25°C (-13°F) requirement.  It is a too infrequent and geographically isolated condition in the continental U.S.
  5. Canadian specifications do not take into account the AC season which is an imperative consideration in Iowa and virtually all the U.S.

I would recommend the following requirements for HRV/ERVs in the U.S.:

  1. Products must be HVI certified;

    Attic HRV installation

    Attic installations can make servicing difficult.

  2. Product must be installed in an obvious location where it will be easily serviceable;
  3. Select and compare units at the airflow specified for the project.  (For any product the higher the airflow the lower the efficiency, the lower the airflow the higher the efficiency.);
  4. The net supply airflows (in cfm) used during testing at these two different temperatures must be within 10% of each other, and specified in product literature and labeling;
  5. If the home is located in a cooling dominated climate, it is advisable to evaluate the Total Recovery Efficiency (TRE) of the product as well as the Sensible Recovery Efficiency (SRE), looking for TREs in excess of 40%.

Supply Temperature

Min. Fan Efficacy at supply tempCFM/Watt (L/s/W)

SRE

°C

°F

SRE < 75%

SRE ≥ 75%

Heating

0

32

1.2 (0.57)

0.8 (0.38)

65%

The following are definitions from Section III of  HVI-Certified  Heat Recovery Ventilators and Energy Recovery Ventilators (HRV/ERV)

Sensible Recovery Efficiency (SRE):  The net sensible energy recovered by the supply airstream as adjusted by electric consumption, case heat loss or heat gain, air leakage, airflow mass imbalance between the two airstreams and the energy used for defrost (when running the Very Low Temperature Test), as a percent of the potential sensible energy that could be recovered plus the exhaust fan energy.  This value is used to predict and compare Heating Season Performance of the HRV/ERV unit.

 

Total Recovery Efficiency (TRE): The net total energy (sensible plus latent, also called enthalpy) recovered by the supply airstream adjusted by electric consumption, case heat loss or heat gain, air leakage and airflow mass imbalance between the two airstreams,  as a percent of the potential total energy that could be recovered plus the exhaust fan energy. This value is used to predict and compare Cooling Season Performance for the HRV/ERV unit.

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