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Humidifier and HRV in the high desert and other HVAC add-on items

BenHM | Posted in Mechanicals on

We’re building a 4200 ft home in the high desert (Bend, Oregon) and are debating several HVAC proposal add ons. The furnace plan is for a conventional ducted system with a Trane modulating furnace and variable speed AC. We unfortunately couldn’t get over the split system interior look. The proposal had several add on items which seem controversial.

1. An Aprilaire Humidifier. It’s indeed quite dry (and dusty) here year round so more humid air would be welcome but several options I’ve hread here and elsewhere seem to question adding a humidifier due to problems the moisture itself presents. Perhaps those problems are dated or just due to the wrong equipment. The contractor bid a steam humidifier but I see there are several choices even from Aprilaire.

2. A 100CFM HRV from Lifebreath was the second option. Although these are $1100 or so to purchase the installed price is $2700 and being a ducted system, I’m less certain I need an HRV. We’re zone 5 here so it gets cold compared to the coast but not insanely so. Should I install this anyway ?

3. One HVAC contractor told me modulating furnaces don’t do well in the high dry climate. He didn’t say why. Is there any truth there ?

4. An electrostatic air filter (Trane Clean Effects). Again what looks like a $500 item that’s a $1300 add on. I’m most suspicious of this one. I’ve read stories of high maintenance and low real-use efficacy once there’s a slight film of dust.

Thanks for any advice.

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  1. BenHM | | #1

    Thanks Steve, Am I looking for a business like "Mechanical Engineering" ? How would I find a good one ? (Bend, OR). The contractor seemed pretty knowledgable. I know they did load calcs but I'm not qualified to evaluate their work which.

  2. user-2310254 | | #2

    The person does not have to be local. You are looking for an HVAC engineer or RESNET rater. There is some good detail in this article. It also identifies a few companies you could consider using.

    You also might want to search GBA using the phrase "hvac engineer."

  3. user-2310254 | | #3


    You should consider hiring a third-party HVAC engineer to complete an aggressive Manual J. The engineer can also spec your system and help you to avoid unnecessary add-ons. I would be wary of adding a humidifier since it is easy for these devices to cause more problems than they solve.

    The ventilation system is probably too small for your home if it is 4,200 square feet of conditioned space. If your house is reasonably tight, you really want a properly sizing and good design to ensure good air quality and comfortable humidity levels. (See

  4. charlie_sullivan | | #4

    A lot of these questions are influenced by how tight the air-sealing of your building envelope is. Have you had conversations with your builder about that? What approaches they are using, whether they are targetting a certain level of air tightness, etc. Generally, if you have an air-tight house, you will need mechanical ventilation, and an HRV is the best way to do that. And you won't need humidification--assuming you have people living in the house who bathe, breath, and/or cook, you'll generate about enough humidity. If it's not quite enough in the winter, you can switch to and ERV instead of an HRV and retain more of that moisture.

    I tend to think that high quality conventional filters are a better plan than electrostatic filters, but I don't have experience or detailed knowledge to back that up.

  5. GBA Editor
    Martin Holladay | | #5

    You've received good advice here. I'll sum up:

    1. Installing a humidifier is always a mistake. The main reason that some homes have dry indoor air is that they are leaky. If you create a thermal envelope with a low level of air leakage, verified by a blower-door test, there's no reason to think that your indoor air will be dry.

    2. Ideally, you will build a tight home. Tight homes need a mechanical ventilation system that is capable of ventilating your home at the rate specified by ASHRAE 62.2. Here's the formula: 7.5 cfm per occupant plus 3 cfm for every 100 square feet of occupiable floor area. If your house has 4 occupants, you'll need equipment capable of ventilating at a rate of 30 + (42 * 3) = 156 cfm.

    For more information, see Designing a Good Ventilation System.

    3. I can't think of any reason why a modulating furnace wouldn't perform well in your climate.

    4. Like you, I'd be suspicious of the need for an electrostatic air filter. In most cases, "keep it simple" is a good principle.

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