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ERV Post Follow Up

Earlier this spring we posted an article on Pre-certified Passive Components: ERV or energy recovery ventilators. The “fresh air machine” of passive homes, including those built by EkoBuilt, ERVs are a vital component and worthy of close inspection. The unit we recommend is the Jablotron Futura Passive ERV and it’s pre-certified by the IPHA.

We fielded a couple of great questions following that post and want to answer them here:

If the ERV is frost-protected down to -20, what happens in areas where the temperature can go down to -30 or -35?

Anytime there are frost conditions, the machines will enter a re-circulation mode to “warm up” the core as required. There will still be incoming fresh air, just less depending on the machine’s efficiency level in extreme cold.

Have you looked at the Panasonic Intellibalance ERV for cold climates? Model FV-10VEC2.

We actually hadn’t installed one of these units before, but at the time this question came in on Facebook we found ourselves on a job where this is what the owner wanted to install, mainly because of cost. They are good units because they are frost protected in the same way that the passive units that we recommend are, however, they consume almost double the electricity and aren’t as efficient. Below we include a side by side comparison at a glance.

Why does the Futura documentation call it an HRV?

Although the documentation (shown below) actually lists the unit as an HRV, it does in fact function as an ERV. As noted in the Futura technical specifications on its website, the unit’s heat exchanger “enthalpy counter-current exchanger with humidity recovery control” means it operates as an ERV.

Jablotron Futura Passive ERV

Power consumption: 0.44 watts/cfm = 44 watts @ 100 cfm

Efficiency rating: 90% at -10°C

Panasonic Intellibalance ERV

Power consumption: 81 watts @ 100 cfm

Efficiency rating: 75% at 0°C

We love the dialogue with home owners, please keep the questions coming!

7 thoughts on “ERV Post Follow Up

  1. Michael Slavitch

    “Anytime there are frost conditions, the machines will enter a re-circulation mode to “warm up” the core as required. There will still be incoming fresh air, just less depending on the machine’s efficiency level in extreme cold.”

    Hello, that’s a non-answer to the question. Reading the documentation from the vendor tells me that the system largely shuts down at -20C.

    “Drying is activated when the outdoor temperature is lower than -20 °C (-4 °F) for more than 16 minutes. Drying stops when the outdoor temperature is higher than -18 °C (-0.4 °F). Low outdoor temperature and Caution is displayed on the control panel. After drying is finished, ventilation and filter check are blocked, boost ventilation is limited to 2 minutes, and the unit continues to run in circulation mode.”

    This is confusing.

    • Thanks for your comment, Michael.

      We appreciate the comment. The information in the design guide does sound confusing to the average person but you have to keep in mind the design guide is meant for engineers and architects who would easily be able to make sense of the documentation.

      The main point to understand is that the Jablotron Futura Passive certified system is able to:

      -operate at extremely low temperatures,
      -defrost itself when moisture freezes at extremely low temperatures
      -continue to bring in fresh air at freezing cold temperatures

      The machine does have to put itself in recirculation mode at extremely low temperatures in order to defrost itself as required and if temperatures remain below -20°C a combination of fresh air cycles and recirculation cycles happen.

      The above is similar for any code approved ERV/HRV on the market, the difference being that conventional systems need to start the recirculation cycles at 0°C where the passive certified units don’t need to incorporate recirculation unless temperatures are extremely low such as -20°C. In most cold climates temperature is usually above -20°C during the day during winter, therefore no recirculation is required when fresh air is in demand.

      I hope you understand now the good behind the system. Any system has limitations but the limitations of a passive certified fresh air system are minimal.

  2. Crystal Leonard

    I have a question about ERV vs heat pump. Are these the same or different? Do you need both in a passive house? We will be building in an area with very cold, low humidity.

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