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Community and Q&A

Adding whole-house humidity in ductless system

HunaHuna | Posted in Mechanicals on

We are building in Michigan and are considering radiant heating and a ductless mini split system. We also like the Lunos heat exchange ventilation system which will deliver some humidity in the winter. We are concerned about maintaining an adequate level of humidity during the winter to protect health as well as art and antiques. Are there systems that do not require traditional ductwork that can manage humidity levels without resorting to a room by room appliance?

Your advice is greatly appreciated!


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  1. GBA Editor
    Martin Holladay | | #1

    First of all, if you install ductless minisplits, they can be used for both heating and cooling -- so you don't need an additional heating system (the "radiant" heating system). Omitting the radiant heating system will save you many thousands of dollars.

    Second, Lunos fans provide fresh outdoor air, but they do not deliver any humidity -- certainly not in winter. When the outdoor air is hot and humid, it is true that the Lunos fans (like any type of ventilation system) will tend to raise indoor humidity levels -- but that occurs at a time of year when higher indoor humidity is usually undesirable.

    The best way to raise the indoor relative humidity of your house in winter (without the use of ducts or individual humidifiers) is to seal leaks in your home's thermal envelope. The lower the rate of air leakage, the higher the indoor relative humidity will be.

  2. Jon_R | | #2

    If you build a well air sealed house, you will find that humidity equalizes well across open doors. In a closed off room with no ducts - you need an appliance.

  3. Yupster | | #3

    Air sealing is definitely key. However, if you are looking to maintain a specific humidity level, sometimes additional humidification is necessary. You might want to look at something like the Aprilaire 800.
    Or if you're looking for something fancy, the Humidifall is a pretty nifty product. Never used it myself.
    Aprilaire also has some systems that can have a small amount of ductwork attached.

  4. Expert Member
    Dana Dorsett | | #4

    More than mere leakage, ventilation rates matter too. In a tight house wintertime humidity levels can be controlled by adjusting the ventilation rate. At ASHRAE 62.2 levels the ventilation can be quite drying in winter, but you don't have to dial it back to where the air is super-stale or polluted to keep it in the comfort & health zone for humidity. During extended cold snaps it may be necessary to dial down the ventilation rate of the Lunos to the minimum to keep humidity levels at a comfortable & healthy ~30%, but most of the time it can be quite a bit higher than that.

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