Indiana ERV vs. Dehumidifier with Modulating Air?

Discussion in 'General Discussions' started by Outtreking, Apr 17, 2018.

  1. Outtreking

    Outtreking New Member

    Hello, everyone. This is my first time to post to this forum. I have visited and read many of your posts over the last few months and found this to be a very valuable forum to help me in deciding to go with geothermal for my new construction home in Central Indiana.

    I have decided to go with a Water Furnace Series 5. My biggest question is concerning fresh air in the house. We will have approximately 2200 sq.ft. on the first floor and 2200 sq.ft. basement with spray foam insulation in the exterior walls and deck of the attic. I have been quoted a whole house humidifier and a balanced ERV system. As I asked more questions, the contractor told me with the spray foam and our environment we are going to be pretty likely to have moisture in the house that will need to be removed. I asked if I should do a dehumidifier instead of the humidifier and the contractor said yes and add a modulating air unit with it instead of do the ERV. He mentioned the ERV systems can get plugged up and usually end up being unplugged due to homeowner frustrations. Another contractor told me if I don't do the ERV then I will get odors lingering from cooking and stale air.

    Can anyone offer any advice as to which kind of system I should look into running or is this something I can leave out for now and determine at a later point what is truly needed with my particular situation?

    I really appreciate all of your help and advice in advance.
  2. ChrisJ

    ChrisJ Active Member Forum Leader

    I have learned a lot on this subject having built my own house with spray foam in the walls & attic floor. I don't have time to write it down right now, after work tonight.

    How many Baths? You can do what's called exhaust only ventilation using bath fans and a passive fresh air vent somewhere in the house. That's the inexpensive way to do it.
  3. Outtreking

    Outtreking New Member


    Thanks for your reply. I look forward to you insight on the subject.

    We will have a full bath on the east and west side of the house (2 total) and a small half bath near the middle on the first floor. Also there will be a full bath in the walk out basement.

    Thanks again for your help.

  4. ChrisJ

    ChrisJ Active Member Forum Leader

    Someday I want add this ERV- Panasonic FV-10VEC1, it's a cold climate ERV, It has adjustable CFM for both exhaust and fresh air and minutes per hour of run time adjustments. With the CFM adjust you could positively pressurize the house a little bit. ERV would have to be connected to the existing ductwork and run the furnace blower whenever it's on.

    What I didn't plan on was the amount of humidity in the house when it was first completed. I had to run a portable dehumidifier during shoulder seasons(Fall and spring) and during the winter first couple years. I still run it when I see the humidity getting up to 50-55%. Lowest I see is high 30's%.

    Back to the exhaust only method. There are timer switches that can turn on the bath fans to run set times per hour.
  5. Outtreking

    Outtreking New Member


    I really appreciate your insight. I like your idea for the bath fan switches. Do you currently use these?

    If you are wanting to add the ERV, does this mean the exhaust only method isn't working how you would like it to? Should I go the route of the ERV rather than the Dehumidifier and modulating air? To be honest, I am not really even sure what the modulating air means or how it is applied in this situation. This method was suggested to me by a potential hvac installer as opposed to the ERV due to his personal experience. Do you think I would be fine with the portable dehumidifier if necessary or is a whole house option going to suit me better?

    Thanks again!
  6. ChrisJ

    ChrisJ Active Member Forum Leader

    I do not use them (yet). I do use my bath fans manually along with running my heat pumps blower on fan only. On a cold, dry day it lowers the indoor humidity a few % points. So the exhaust only does work, would be a lot more hands off if I got the fan switches. Some of this building science/indoor air quality stuff depends somewhat on how tight the house is built.

    After my house was spray foamed (open cell in 2 x 6 framing) the building inspector insisted I need a vapor barrier and when the foam was shaved off even with the studs I no longer had a vapor barrier. So the insulation people cocooned the whole inside with poly sheeting(plastic). I have not done a blower door test to see just how tight the house is (infiltration rate). Exhaust only works because fresh air is drawn in through little cracks and gaps in the house envelope. Putting a passive vent (hole in the wall) assures that the fresh air comes in where you want it to not from all the little gaps.

    They make whole house dehumidifiers that bring in fresh air but they use a lot of electricity compared to an ERV or HRV. So no I would not do the modulating fan thing(don't know exactly what he meant either). ERV's & HRV's will work fine and not get clogged up if they are maintained properly, checking and cleaning(replacing) filters semi-annually or on whatever schedule the manufacturer suggests.

    If I were doing the house over again: I would do the Series 7 variable speed Waterfurnace. Especially if you are doing zoning.

    I would do the ERV with it own ductwork, if you can afford it. Otherwise do the bath fans with timer switches & passive inlet.

    I would do ridged insulation on the outside of the house with cellulose in the framing cavities.

    Raised heel trusses for the roof so you could have deep cellulose in attic all the way over to the top plates of walls.

    Good luck with your new home build, ChrisJ
  7. Outtreking

    Outtreking New Member


    Thank you for all of your time in giving me your input.

    Good luck with your future modifications.


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