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Who is using low cost IAQ monitors? What are you learning?

I've deployed over 30 Foobots and they've taught me a number of things:

1. If you use positive ventilation on a closed cell spray foam job with a blower door, tVOC levels stay under normal levels
2. If you don't use enough ventilation, it took the tVOC levels in one home 4 days to normalize
3. You can use them to give feedback on whether or not damper adjustments equalize temps between floors
4. tVOC was a good proxy for success with a mold sensitive client. Their CO2 levels stayed low as well with their own monitor.
5. Watch for high RH to combat mold/mildew/etc.
6. I'm trying to deploy 3/home, one on each floor. You can watch how well contaminants move around.

Unfortunately, I haven't had many clients express interest in actually buying them. For now I'm leaving them placed for a year or so. I want to watch changes between seasons. I'm learning a ton through continuous commissioning, or continuous optimization as Linda Wigington called it. After the year, I'll be moving them to other client homes. I'm hoping to find a way to get more clients to buy them, because they are great for diagnosing problems.

Here is my album of dashboard photos: http://bit.ly/FoobotDashboard

Here is my article from last summer comparing 7 of the monitors: http://bit.ly/IAQMonitorComparisonESHP

Who else is experimenting with them? Which one? What have you learned? What do you like or dislike?


  • Brad CookBrad Cook Posts: 153
    I deal mostly with existing homes- problems created by builders. I have monitored several homes with IAQ issues (mainly high RH). I am in Zone 6 in central Vermont. The problem that I am encountering in some homes is where the client wants to keep part of the home at a 10+ degree temperature difference from the rest of the home, such as keeping a Master Bedroom suite much cooler for sleeping at night. The challenge is to not only control the RH, and thus the Dewpoint, but to do it with outside air temperatures swinging as much as 60 degrees in 24-48 hours. The warmer outside air can hold a lot more moisture, so we don't want to be bringing in a lot of warm outside air if the outside temperature is going to drop 50-60 degrees in a day. We are trying to avoid the dewpoint, particularly on the well insulated windows.
    I have been using Acurite's remote sensors and bridge to monitor temperature & RH throughout these houses and outside them. The app allows me to monitor these areas from the internet and analyze the date using charts and graphs.
    I do have sensors that I have used for monitoring CO and CO2 levels, but they are data loggers without the remote capability.
    From what I have read about the Foobots, they are useful but have their drawbacks. Monitoring for Temp. & RH to control ventilation is tough enough. I think that adding CO2, CO and VOCs to the mix makes ventilating even more complicated.
    The big issue that I see is that most occupants are not aware and savvy enough to manually control their own IAQ, and ventilation controls have a long way to go to be autonomous.
  • Nate AdamsNate Adams Posts: 569
    Brad, you bring up great points! And yes, it gets complicated fast. I've found that by adding PM and tVOCs to the mix, the learning accelerates (which often means frustration...) Then you have two proxies aside from RH as well. PM is a good proxy for filtration. tVOC sensors pick up all sorts of stuff, but if it's high in a bedroom, the odds are it's CO2 from sleeping clients. Thoughts?

    Also, which model Acurite are you using? I didn't know they had datalogging ones.
  • Nate AdamsNate Adams Posts: 569
    Also, I keep working on the hypothesis that a decent shell combined with right-sized HVAC that runs all the time for continuous filtration and fresh air injection/mixing solved most IAQ problems. 10 degree swings, though, not likely with forced air without zoning and a bunch of side effects.

    Do you have a hypothesis you work to?
  • David ButlerDavid Butler Posts: 3,889
    10 degree swings are not uncommon in homes with woodstoves since folks tend to keep the rest of the house cooler. That's usually not a problem in a leaky home since infiltration keeps the house very dry.

    When I interview new construction clients in cold climate zones, I make sure they understand how having a tight envelope means higher RH levels in winter. This will make their home more comfortable, but they can't let rooms get so cool that mildew or mold grows. Some folks become so accustomed to sleeping in a cool bedroom that they end up cracking a window at night. I don't try to tell them they can't do that, but I make sure they understand the consequences. I help them identify a closet or other corner that's likely to be the coolest point in the house and advise them to monitor the RH with one of those desktop displays with remote sensor. Of course, the presence of mold is a pretty good indicator of a problem.
  • Brad CookBrad Cook Posts: 153
    Nate, for Acurite products, start with the SmartHub, which connects sensors to the internet, then add up to 10 sensors per SmartHub. There are a variety of battery operated remote sensors available. I have been using Temp./RH sensors that are weather-proof and sensors for indoors that also have a digital display on them. You can set up an Aculink account on-line to remotely monitor several locations. I just ordered, on sale, the Pro 5-in-1, which measures Temp., RH, barometric pressure, wind speed and direction and rainfall. Check them out at Acurite.com

    David, good points- "It is all about the dewpoint". I have seen so many scenarios where even a reasonable (30-50%) RH meets the dewpoint and encourages mold growth (closets on exterior walls with lots of "stuff" in them, upstairs bedrooms closed off and heat turned down/off, etc.)
  • David ButlerDavid Butler Posts: 3,889
    edited March 2017
    Brad Cook said:

    ...I have seen so many scenarios where even a reasonable (30-50%) RH meets the dewpoint and encourages mold growth...)

    Maybe just semantics, but mold won't grow when RH is 50%. Mold doesn't respond to dewpoint, it responds to the RH. If dew point gets too high relative to a surface temperature, then the localized RH can exceed the mold growth threshold, usually considered to be 70% RH although some types of spores can establish as low as 65%**

    For example, if typical ambient is 69F @ 50%, that equates to 50F dew point. Since vapor diffusion depends on dew point, the dew point will equalize and thus be relatively constant throughout the house (although local dew point will temporarily spike when there's a high moisture event such as a shower). Since RH is relative to temperature, RH can vary dramatically in warm and cool spots. If the dew point is 50F, the localized RH will be high enough (70%) to grow mold on a 60F surface. So it's the cool spots we have to watch out for.

    Note that low ambient RH is irrelevant if a surface material contains moisture (although if ambient RH remains low, the surface will eventually dry below the threshold).

    I know you already know this stuff, but a lot of folks are confused when it comes to RH vs dew point. Hell, I've taught psychrometrics and I still get confused sometimes!

    ** Here's an EXCELLENT presentation by Lew Harriman from the 2014 Dry Climate Forum (24MB). He dives deep into the consequences of high RH and explains how surface moisture impacts mold growth. In my opinion, this presentation is the gold standard for practitioners who want to learn about mold in buildings (24MB).
  • Brad CookBrad Cook Posts: 153
    Yes, David, I am aware of those facts. Mold will grow when a surface is at or below the dewpoint, resulting in a wet surface. Mold will grow can grow when the temperature is not too cold and RH is >65-70%. I am talking about the 1970 condos with electric heat and wood stoves, where there is R-19 in the ceiling and a pot of water on the wood stove (because wood heat is dry, right!). That is mold on the ceiling from condensation. I am talking about 1970 condos with damp crawl spaces and many of the units are second homes for this ski area. Stuff is packed into the floor of the closets, the door closed and heat turned down to about 50 degF. That air sees the dewpoint on the exterior walls (R-11) of the closet when it is very cold out because the "stuff" is helping to keep any inside heat from the wall. Condensation ensues followed by mold growth. The two story house where the kids have grown and left the nest. The parents are older and keep the heat at around 72 degF in the winter. They turn off the heat in upstairs bedrooms and close the doors, but the warmer air still leaks into those rooms and moisture condenses on the poorly insulated walls and ceiling, resulting in mold growth. Then there is the 10 year old house that is quite tight (2.6 ACH50) but no regular ventilation ("but I run the bath fan all day!". Compounded by the fact that they keep the Master Bedroom abut 10-12 degF cooler than the rest of the house, and they wonder why they have to keep wiping water off of the windows when it is fairly cold out.
    Oh and then there are the basements that were flooded in the summer and they are only using fans to push that moisture out (and bringing in warm humid air to condense on the cooler basement walls. Yes, you need to heat up the basement in the summer to dry it out.
  • Nate AdamsNate Adams Posts: 569
    Brad, those examples have serious meat on their bones! How do you coach those clients, particularly the 50 degree and closed off bedroom examples? Do you have access to metrics in any of those homes to see if your suggestions take root?

    I'd say I have about 75% luck in changing behavior. My goal is to change the house enough that clients stop doing dumb things like that. Granted I can't imagine succeeding with the ski lodge homes...
  • Nate AdamsNate Adams Posts: 569
    I should add to my last comment that I like to use metrics to slowly bring clients up to speed on Building Science and IAQ. I'm just an ok teacher, but the slower I go and the more I let clients come to conclusions after educating them on basics, the better the results are. Well educated clients often add a lot to the upgrade process, they make suggestions that make upgrades work better. It's a great feeling when you get partners and you aren't dragging people along kicking and screaming. =)

  • I just saw this article that does an informal survey of research on CO2 levels and the impact on cognitive ability. It mentions a couple of monitors not mentioned in Nate's in-depth comparison linked in the original post. In particular, the one by AZ Instruments caught my attention. It has its own display and logs 4-minute temp/RH/CO2 data that can be downloaded to a PC app (optional).