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HRV or ERV With or without dehumidification for SIPs house in Colorado situated at 7500′?

Jim Lane | Posted in Green Building Techniques on

The house will be very tight and will require an air exchange system to limit retained moisture and prevent condensation in the SIP panels on the roof at cold temperature. The house is 2600 SQFT and is a story and a half. All internal SIP seams will be sealed with the tape that the SIP manufacturer supplied and all window and door frames will be seal with foam. The HRV or ERV will be connected to the baths, mudroom and kitchen for off-take and input into the bedrooms and living room. There will be no AC system installed. The heating system will be hot water baseboard radiators. It has been estimated that the heat loss will be 35KBTU at -15F.

The locality has very low humidity most of the time and can get quite cold (-20F) to warm (90F). There have been issues around mold formation in the roof panels due to condensation from warm moist air moving from the house through the roof panel.

So, which should be used HRV or ERV with or without dehumidification?

Thanks

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Jim,
    In the dry climate of the high-altitude Rockies, there should be no need for a dehumidifier.

  2. Brendan Albano | | #2

    Is this a situation where the vapor diffusion ridge vent discussed in this BSC article would be relevant? https://buildingscience.com/documents/insights/bsi-088-venting-vapor

    They were a solution proposed to address ridge rot on SIP homes in Alaska.

  3. Reid Baldwin | | #3

    You have stated your problem as excessively high indoor humidity when the outdoor humidity is low. In that situation, vapor recovery in the ventilation system will work against your goals, so an HRV would be preferable to an ERV.

  4. Expert Member
    Dana Dorsett | | #4

    An HRV operating under dehumidistat control would limit the wintertime risk just fine, and in summertime there is no risk.

    An ERV's core is more susceptible to ice damage than HRVs, and provides no significant benefit over an HRV in a cool dry climate.

    So if the question is ERV vs. HRV, it'll be HRV, no question!

    Active dehumidification would only be necessary if you're running ventilates EXTREMELY low, or have significant humidity sources such as a large tropical fish collection or an indoor cannabis cultivation hobby or something. Most homes in CO would literally never need active dehumidification- the outdoor dew points are low year-round, and the average latent cooling loads in summer are negative. Ventilation alone takes care of it.

    When the concern is about exfiltration leakage at SIP seams there can be an argument for exhaust-only ventilation, depressurizing the house so that any air passing through leak points is dry outdoor air, but HRV under dehumidistat control in winter works just as well or better.

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