I posted a video on ERV's and one of our subscribers started asking lots of questions about the design. I was able to answer most of them, however he wanted validation on several products that his HVAC provider was recommending. I gave him some general answers, however I did not have experience with the products that he was going to us and wanted to know if you all had any feedback on these:



Here is the video with the original thread: https://youtu.be/kwb05lL6hZI

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  • I am a poor salesman, although I have tried many times, but something I learned in college really stuck with me. "Create a need and then fill that need". I see it with toothpaste ads today. "Acid is eating away at your tooth enamel. You need to use our toothpaste to protect your teeth!" Germs are everywhere in your house! You need our product to keep your home germ-free!"

    I am seeing more of that with UV systems for furnaces. UV systems do not make the house dust-free, and they do not kill all viruses. Why are people trying to make their environment sterile? That will only prevent the body from developing natural defenses against various bacteria. If you have mold in the house, then fix whatever is allowing the mold to grow, rather than trying to kill the mold as it keeps on growing.

    Your YouTube video is about a Panasonic ERV. The salesman was not speaking the whole truth, because it seems that he doesn't know all of the facts. From all that I have read and all of the sales reps at trade shows that I have queried over the past several years, ERVs are generally not preferred over HRVs in colder climates (you don't indicate where you are located, which is always an important fact to note). There are 2 types of ERVs, the kind with the enthalpic wheel and the kind with the enthalpic core. The kind with the wheel is definitely not recommended in colder climates. The kind with the core will work in colder climates, but not necessarily more efficiently (usually less efficient). Some of the basic facts are that water vapor wants to go from high concentration to low concentration (the same with heat aways going from hotter to colder). That higher and lower concentration of water vapor is not just about relative humidity, but also about temperature and pressure. Both HRVs and ERVs have issues with condensation and freezing, when the warm moist outgoing air meets the cold incoming air. The HRV has a drain for condensation and when it is below freezing it will go into a defrost mode periodically. The ERV does not have a drain, but it will have ice buildup inside the core and it also goes into defrost mode periodically when below freezing. The colder it is outside, the more the ERV needs to defrost, compared to the HRV.

    Finally, using an ERV (or HRV) to ventilate a bathroom is a bad idea. The ERV or HRV has a hard enough job dealing with average moisture levels in a cold climate, and adding moisture from a shower will make it worse. Note that the instructions for the smaller Panasonic FV-04VE1 ERV specifically states "Never install the unit in a high humidity space, such as a bathroom, kitchen or laundry room".

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