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ERV advice for a new ERV contractor

SanjayGarg | Posted in General Questions on

Hi,

My family and I are building a new home and we are trying to make it as safe as possible for our immuno compromised kids.  We hired an HVAC engineer to design our HVAC and have an estimate from our HVAC contractor on that.  we are also putting in aerobarrier.  and the last step is our ERV.   We want to make sure our HVAC contractor, who is new to ERV, is properly designing our system.  We are planning on using 2x Panasonic Intellibalance 100 systems).  Do you have recommendations for 1. air intake/stale air locations (currently 4 bathrooms and 1 laundry) 2. fresh air locations (currently  4 bedrooms and 2 offices) 3. types of registers to use in each location 4.  do i need to hire an ERV designer for this or is this pretty straight forward?

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Replies

  1. Jon_R | | #1

    Make sure that the outlets are measured to have the right CFM (eg, 15 CFM per person in a bedroom). And have sufficient throw/velocity to create good mixing.

  2. user-2310254 | | #2

    Sanjay,

    What is the square footage on the house? I would be surprised if your HVAC engineer could not spec this for you. Have you asked him/her?

    PS. Note that an HVAC contractor and an HVAC engineer are not necessarily the same thing. HVAC contractors often run Manual Js. But the feedback here is they often grossly oversize the system requirements.

    1. SanjayGarg | | #4

      HI Steve, the home will be 4600 square feet. With around 3400 on the first/main floor and 1200 sf on the 2nd/top floor. Our HVAC contractor suggested working with an HVAC engineer who we hired for the HVAC design. He'll also be doing Aeorbarrier for us. Our HVAC guy, who hasn't yet installed any ERV's, seems to understand not to oversize sysetems but our engineered HVAC design validates that.

      I am concerned about paying and installing an ERV system and not desiging it rigth. I really appreciate all the great input from this community already! I am really thankful this site exists!

  3. Expert Member
    AKOS TOTH | | #3

    I would have a largish stale air pickup near the kitchen area (65cfm). Cooking is typically the largest source of indoor air pollution, even something as simple as making toast will cause your PM2.5 to skyrocket. Make sure to also install a boost switch in the kitchen, it is the one I use the most.

    I would run a dedicated exhaust fan for the most used bathroom in the house, I find that this works better than the ERV for me. I almost always use the exhaust fan instead of kicking the ERV to boost as it is more effective. This would also free up some extra capacity for the stale air pickup for the kitchen.

    Install a filter box on the fresh air intake and feed each unit from that. This would give you the option of having much better filtering and replacement filters these are much cheaper the ones in the unit. A MERV13 filter would also keep the filter inside your ERV pristine. If the filter box is inside conditioned space, it needs to be insulated. If it doesn't come this way, this could be done by wrapping it in about 1" to 1.5" of rigid, just make sure there is an easy way to open it to change filters.

    The stale air pickup from your laundry room should have a filter on it. I use one of those washable filters. Dryers tend to produce a lot of lint which you don't want in your ducts or making its way to the ERV.

    1. SanjayGarg | | #11

      Thanks for this advice Akos. I met with the HVAC contractor/ERV guy this afternoon and made changes to our layout per your recommendations. We are looking to add... 1) filter boxes for each unit near the outside fresh air intakes, 2) exhaust fans in the bathrooms as a secondary assist, 3) stale air intake in the kitchen. Should we have a filter on both the kitchen and laundry? and do you recommend the fantech style exhaust and fresh air grills? MGE4 and MGS4.

      1. Expert Member
        AKOS TOTH | | #14

        Generally, you always want an intake filter on any duct. Much easier to change these and keeps the ducts and hvac equipment pristine.

        Zahnder sells on for their return diffuser, but there are plenty other off the shelf ones as well. I like the mud in ones (aria vent pro) for a clean look but you have to DIY a filter into it.

        https://smallplanetsupply.ca/filter-for-return-diffusers/

        Try to pick one size you can use in multiple places, fewer replacement filters to keep around.

        The kitchen pickup should be kitty corner from your stove. You only want it to pick small particulates and smells not vaporized oil from the stove.

  4. user-2310254 | | #5

    Sanjay,

    That's a lot of house. If you have the budget, a Zehnder HRV or ERV would be on my short list. Zehnder also could design the system for you. I've also read good things about the second generation Panasonic IntelliBalance system, and you could contract with someone like Energy Vanguard on the design.

    The formula for calculating code minimum ventilation rates isn't that complicated. (See https://www.greenbuildingadvisor.com/article/how-much-fresh-air-does-your-home-need, for example.)

  5. STEPHEN SHEEHY | | #6

    Second the Zehnder recommendation. We emailed the drawings and Zehnder designed the system. From a big pile of tubes and various items, after installation, hardly anything didn't get used. My electrician installed it and was impressed at how well everything went together. And Zehnder commissioned it.
    For what you'll be spending on such a large house, the extra cost for a premium product may be money well spent.

    1. SanjayGarg | | #7

      Hi Steve, our HVAC guy is charging around $6K for two Panasonic Intellibalance 100 systems. Is the Zehnder around the same or would it be more?

      1. Deleted | | #9

        Deleted

      2. STEPHEN SHEEHY | | #10

        Probably more for two systems, but I'd check with Zehnder. You might not need two.
        My system takes a MERV 13 filter, which is plus.

  6. user-2310254 | | #8

    My guess is the Zehnder will be quite a bit more expensive. Stephen may be able to provide more info.

    1. SanjayGarg | | #12

      Thank you. I emailed the plans to Zehnder Monday and hope to get something back before the end of the week.

  7. drewintoledo | | #13

    Zehnder price is sky high making it unreachable to someone like me, therefore I will build with Broans erv140te.

    I spoke with Broan Technical support and they recommend against placing the return lines in the kitchen and bathroom due to the amount of pollutants (grease, steam, etc) that the ERV isn’t designed to handle. I did mention that I take Very hot, steamy But showers maybe that’s not the case in your situation.

    It wouldn’t hurt to call the manufacturer and bounce some of you questions off of them. If you do, please report back to this thread and let us know what you’re told.

    1. Expert Member
      AKOS TOTH | | #15

      There is absolutely nothing wrong with putting a return in a bathroom. ERVs are designed to exchange moisture, about the only thing it will do is humidify the return air a bit more. There will also be a fair bit of dilution as the pickup in the bathroom is usually no the only return. Even with steamy showers, the air that makes it to the ERV will be just a bit more humid than typical house air.

      Kitchen return is also not an issue as long as it is far from the stove.

      Zehnder, in their install manual, specifically call out returns in both kitchens and bathrooms.

      Not sure where Broan tech gets their ideas from, but their unit is a re-badged VanEE. VanEE's install manual also shows pickups in the bathroom and kitchen (provided not directly connected to the range hood).

      P.S. Zahnder unit itself is not that expensive. What drives the cost of those is the piping and other accessories. Just as a box, price is comparable to most high efficiency offerings.

  8. user-2310254 | | #16

    On my HVAC engineer's recommendation, I put a Panasonic FV-04 in the master bath of my previous home. It was a disaster. The ERV might have been able to handle the moisture, but the FV-04's circuit board could not. I replaced the soldered in fuse a couple of times before deciding to move the unit to a dryer location.

    Now, moisture may not be an issue with more sophisticated HRVs/ERVs. (The FV-04 is a budget unit.)

  9. TMinor | | #17

    Personally, I'd stray from ducted mechanicals. They are a breeding ground for all kinds of immune compromising mold/bacteria/viruses, etc. Even with amazing filters in said system, the ducts will become dirty and simply push around the filth (especially if not sealed fully during construction as most dust and filth settle there during the construction time period.)
    Each room should have its own dedicated heating/cooling...sounds pricey but perhaps think about ceiling fan for use during hot months (use in conjunction with proper window placement/awning/glazing), and perhaps options like radiant floor or baseboard for heating.

    Even with the "best" hvac system, filters, and seasonal cleaning, ducts will always breed filth.

    Just my 2cents. Good luck!✌

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