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Community and Q&A


James Magner | Posted in Mechanicals on

I am planning on installing 2 minisplit heat-pump units to heat and cool a home we are building. It is a new home just south of Boston, MA, about 2,800 sq. ft., tightly constructed, R-35 walls, R-55 ceiling.

The Manual J and D calculations have been done, indicating I would need approximately 33,000 BTU to heat and under a 2-ton system to cool. I am planning on meeting with a minisplit heat-pump rep to discuss the best options for the home.

However, the engineer that performed the calculations for my home also recommended an ERV coupled with the minisplits for the most comfortable and efficient system. I am not clear on the differences between the HRV and ERV and am not sure which is best in my situation.

What I thought I understood from the engineer was that the ERV would assist in not only providing fresh air to the living spaces but also to move the conditioned air around the house. Is that accurate? I also feel that some of what I read about ERVs is that they are more for warmer climates, while HRVs are for cooler climates.

Any direction or feedback on this would be appreciated.

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  1. User avatar GBA Editor
    Martin Holladay | | #1

    Either one will work.

    A well designed mechanical ventilation system will deliver fresh air to the rooms where it is most needed (usually the living room and bedrooms) and will remove stale air from rooms that usually generate odors (generally the bathrooms and laundry room, and sometimes the kitchen). Either an ERV or an HRV with dedicated ductwork will perform these functions well.

    To learn more about the differences between the two types of ventilation appliances, see HRV or ERV?

  2. James Magner | | #2

    Thank you for the reference Martin, I apologize for the superfluous post. I got most of what I was looking for and a whole lot more reading through all those entries. One thing I am still wondering is if you draw the air from the baths and sometimes the kitchen with the recovery ventilators, in the baths specifically do you still need to install traditional ventilation fans? Also, in a cold climate should one consider getting an hrv or erv with a heating element?

  3. User avatar GBA Editor
    Martin Holladay | | #3

    Although you will occasionally hear some builders advocate for a supplementary bath exhaust fan, I don't believe you need one -- and neither do HRV and ERV manufacturers. Most HRVs and ERVs include an override switch in the bathroom that pushes the exhaust fan into a temporary higher speed.

    Different manufacturers have different control strategies to address very cold temperatures. Some HRVs shut down in very cold weather, while others recirculate a fraction of indoor air to prevent the core from freezing. Still others may include an electric resistance heating element (which of course increases your energy costs). Consult the manufacturers to discuss cold weather features and operation.

    Most homeowners don't notice reduced ventilation levels in very cold temperatures.

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