ERV vs. HRV

Post date: Mar 2, 2015 2:37:39 AM

What are those acronyms? You thought I was allergic to acronyms! Well, yes, I am allergic.

• HRV = Heat Recovery Ventilator a fan-based system that continuously exchanges indoor and outdoor air, while preserving most of the heat.
• ERV = Energy Recovery Ventilator is similar, but uses a rotating membrane to keep most of the humidity on the side it originated. That is, if it is humid outside (read Florida in summer), that humidity is kept outside. If it is humid inside and dry outside (read Taos in winter), that humidity is kept inside.

Why an energy recovery ventilator and not a heat recovery ventilator? As I understand it, the ERV is primarily useful in high humidity areas. See Broan web site. Taos is not a high humidity climate.

Green Building Advisor is less clear (in many more words) but I read it to say that in a small, tight house in a cold dry climate, an energy efficient ERV is the right choice.

In addition, dpoint technologies (manufacturer of the membranes that extract moisture) says, “Recent studies have concluded that ERVs should be used in cold dry climate zones because of improved comfort, no drain required for condensation and less energy for defrost.” In dry climates, the ERV might actually preserve indoor humidity in winter, making the house more comfortable.

Operating cost is the critical factor here, since the fan runs continuously. The specified model for my house, Aldes E150-TRG, draws 156 Watts, per spec, or 1310 kWh/year or about $130/year for power, plus maintenance. It appears that the specified model is maintained from the front, while some have slide-out filters that require access room.

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