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Sheathing data logger

Yupster | Posted in General Questions on

I’m working on a house with brick veneer that was built in the ~1970’s without weepholes or base flashing and the 1″ vent cavity is almost entirely filled with mortar. I’d like to add a data logger in my walls to track the moisture content of the sheathing, for personal interest. It’s two layers, 1/4″ OSB sheathing over 1/2″ fiberboard. I was wondering if anyone could point me towards some reasonably priced sensors & data loggers that would work for this. Something that wouldn’t require a lot of user interaction to produce useful data as well. I know that if I have to put it into a spreadsheet and graph it I’ll never get around to looking at the data.

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Replies

  1. Expert Member
    Michael Maines | | #1

    Yupster, the two most common brands for this are Omnisense and Onset. We used Onset's Hobo loggers in the last house I designed, to monitor temperature and RH in the walls, and to save money we went with bluetooth transmission--when I drive up to the house, my phone collects the data, and I can use their free software to see what's happening. On a current house the same builder (Emerald Builders of Bowdoinham, Maine) and I are talking about either doing the same, or switching to Omnisense, which is what Building Science Corp uses for their experiments. An advantage of Omnisense is that it can record wood moisture content in addition to temperature and RH. Both products have a range of loggers and ways to transmit and review data. All of it has a steep but short learning curve. Onset has good customer service (I'm sure Omnisense does too) so just call or email them for more info.

    https://www.omnisense.com/
    http://www.onsetcomp.com/

  2. Yupster | | #2

    Thanks, that's some great info. The Hobo logger is more in my price range but doesn't log wood moisture content. I think I would need that to get anything useful out of the information. Guess I'd better start a data logger savings fund!

  3. Yupster | | #3

    I guess you could estimate the WMC from the temperature & relative humidity from one of those HOBO loggers if you had long periods of stable values. Is that what you do with your results? Or is your data for something else?

  4. Expert Member
    Michael Maines | | #4

    Yupster, that is/was my plan, figuring that we know the temperatures and RHs at which moisture will accumulate, and we can track it over time. I say "is/was" because I am having some trouble with the loggers at the moment, and in the meantime I've talked with Kohta Euno and Chris Corson about it (they gave an influential talk at the NESEA conference a few years ago, summarized here https://www.greenbuildingadvisor.com/blogs/dept/musings/monitoring-moisture-levels-double-stud-walls.) They say that wood moisture content (WMC) is the more important measurement--they aren't as concerned if moisture COULD accumulate; they want to know if it IS accumulating. A somewhat fine distinction, in my view, but perhaps an important one if hovering close to the tipping point.

    Coincidentally, I was working with Chris Corson when he was putting that presentation together, together in a very small office, but I was involved in other aspects of the business and never thought about the importance of the WMC.

  5. Yupster | | #5

    Hm, that is a good point. Thanks for the heads-up. This is exactly the advice I was hoping to get.

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