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HVR vs. EVR vs. whole house humidification

metar28 Member Posts: 10
Hello. We are building a new house in the Hudson Valley region of New York. It is a 3370 square foot bi-level design. We will use hot water baseboard heat (5 zones) using a mod con gas boiler. We will also have central air using a 5-ton SEER 16 unit. The house envelope will be tight. (We are doing upgraded insulation.)

My heating guy advised me to install a HVR system to improve air quality and said I should talk to the AC guy about incorporating one. The AC guy said I will need a stand alone unit since it's not a good idea to leave the AC system open in the winter because of heat loss.

Someone else told me to save my money on a HVR and instead get a whole house humidification system that regulates humidity by either adding or removing as necessary. Well, that sounds good because I always get a dry nose and very dry, chapped hands in the winter and anything to help that would be appreciated. But, once again, isn't a whole house humidification system something you tie into the central AC ducting?

I suppose if I were using forced air heat then all this would be easy because the HVR and humidification control would be run through the same ducting.

What about installing a stand alone EVR? Would that solve my air quality (staleness) issues and humidity problems?

Trying to figure out the most economical and effective solution. Thanks!


  • Ironman
    Ironman Member Posts: 6,705
    edited August 2011
    Not Sure...

    What your A/C guy means by "leaving the system open", but HRV's , ERV's and humidifies normally connect to a ducted system. There are stand alone options, but unless your duct work is in an un-conditioned area, I would connect them to the duct system.

    I don't know of a unit that both humidifies and de-humidifies. Your A/C will take care of de-humidification and a humidifier will add moisture in the heating season.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    I had one that humidified and dehumidified.

    I had an A-C unit that both humidified and dehumidified for a large minicomputer. Computer  was in 4 or 5 boxes each the size of a refrigerator. And two disk drives each the size of a top-loading washing machine.

    It was a big box that took in chilled water and returned the slightly warmed up water to the building system. Inside the box was a proportional thermostat that controlled a proportional water valve that was in series with the chiller coil. Also in there was a bunch of resistance heaters across the 220 volt power line for reheat. And a tub with three calrod heaters in it and a water supply with a valve like in a toilet tank. And some clever thermostats and a hygrostat or two. And a big blower.

    As the room warmed up, the water valve opened, the hotter the room got the more the valve opened. If the room got cold, the valve bypassed the cold water, and as the room got colder, more water was bypassed. That way, we could easily control the room temperature to +|- 1F.

    If the humidity got too low, the cal-rod heaters in the water tub were turned on to boil the water. There was an overflow tube in the tub that allowed water to flow out of the tub. The fill valve was set so that the water level just did not overflow. When the water was boiling, a trickle of water overflowed. This reduced the calcium deposit build-up. That did the humidification. If the humidity got too high, the controls turned up the reheat to maximum and this indirectly raised the chilling a lot. The excess humidity condensed on the chilling coil and ran down a drain. This was all in a box about the size of two refrigerators. It took in air from the top and blew the conditioned air straight down into the raised floor. Vents in the floor directed the conditioned air where is was most needed.

    This unit was custom built by the company who provided the raised floor. They did not know much about electricity or controls, so we had to do a little re-wiring, but I imagine a competent company could have provided one that worked properly from the get-go.
  • metar28
    metar28 Member Posts: 10
    What about the Aprilaire?

    My sister in TN has an Aprilaire. She said the system adds or takes out moisture to keep the house at a specific relative humidity. What about something like that? 
  • BillW
    BillW Member Posts: 198
    ER/HR ventilators

    Heat recovery ventilators tend to reduce interior humidity levels, because they recover sensible heat. They need a drain to drain the condensate from the de-frosting process.  Energy Recovery ventilators tend to balance indoor/outdoor humidity levels because they recover both sensible and latent heat.  They do not require a drain.  If your house is tight, and you have a ducted AC system, you can duct the ER/HR unit right into it, and utilize the AC fan to move the air around.  Put the intake above the snow line, and away from dryer exhaust, car ports, boiler exhausts, garbage cans and pet areas. A steam humidifier (self contained) can provide humidification and a small reheat coil, connected to your hydronic system with a zone valve that opens when the system is activated, will take the chill off any air circulated in the ducts.  You can tie it all together with one thermostat, several manufacturers have them.  Generally, ER/HR ventilators run at low speed all the time.  They can be programmed to run at higher speeds at certain times, on manually sped up for parties and gatherings when more people are present, and food preparation and smoking might be occurring.  They are not kitchen exhaust fans, and don't replace them, but they do dilute and exhaust odors.  You may need more than one unit to get the desired number of air changes per hour, your AC contractor can tell you this.  I hope this is useful.
  • Ironman
    Ironman Member Posts: 6,705

    Aprilaire makes several models of humidifiers. I'm not aware of them making a unit that does both. As JDB has pointed out, there are commercial systems that do this, but I've never seen anything in residential.

    Removing moisture from the air (de-humidification), requires chilling the air below the dew point. This normally means that some form of refrigeration system is necessary. And again, this is the job of the A/C system. If it's done right, you don't need anything else to de-humidify.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • BillW
    BillW Member Posts: 198

    Energy Recovery Ventilators use either a dessicant wheel or a hygroscopic paper core to transfer humidity.  The dessicant on the wheel catches water vapor, and transfers it to the side of the lowest water vapor level as it turns thru the air stream.  Hygroscopic paper does the same thing, but those cores are stationary.

    They balance humidity, moving it from the airstream with the higher concentration to the lower; they do this passively without mechanical cooling.
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