Are indoor air monitors worthwhile?
build2580
| Posted in Green Products and Materials on
I have recently gotten notices of the release of Blueair and Awair. I am sure there are others on the market as well. Are indoor air monitors worthwhile? Accurate? Useless? I know that inside a tight house air quality can be more of an issue than an old leaky house, but is monitoring the best way to address the potential problem or some other approach?
Thanks
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Replies
Monitoring rarely solves anything. And what will you do if you find 50 picoCurrys/liter of (insert random chemical)? (Yes, that's a made-up unit.)
Without looking up the specific monitors you reference, in general I'd be leary of "air quality" monitors or air purification systems. There's no logic or science behind many. To give you the proper attitude towards claims made by various companies hawking their wares, read Lstiburek's BSI-017: Blame in on Star Treck: Solving IAQ Problems. (If you don't like to read much, just read the boxed summary of Lessons Learned on page 1.)
Or look for Martin Holladay's responses to people asking about "toxic" houses.
Or look up a response by Daniel Ernst from July 17, 2010, on the topic of air purification systems.
What would I be interested in monitoring? Temperature, relative humidity, and CO.
And, CO2 seems to me to be a reasonable proxy for ventilation rates. Some recent articles suggest that commonly found levels of CO2 make you stupid (er, perhaps). So, I purchased a CO2 logger recently (that also measures temperature and relative humidity) and have started running some tests at home. First place I put the CO2 monitor was in our bedroom. Levels went up and down, kinda as suspected, depending on how much time we spent in there, but I found two interesting things immediately. One was that the CO2 level went up rapidly when we closed the door to the master suite at night. The volume of our master suite is ridiculously large (total SWAG, 7000 ft3), but the CO2 level doubled from less than 500 ppm to over 1000 in only five hours, with no addition dogs, kids, etc in the room. According to said studies, 1000 ppm is enough to make you measurably slower mentally. A rise that rapid got my attention.
Secondly, I found that the high level dropped immediately when our forced air furnace kicked on and started circulating air. This is good, except that during much of the year, including this very extended shoulder season, our furnace doesn't run much, if at all, especially at night when the thermostat is set back. Short term - I don't close the bedroom door at night anymore.
Sorry for the wandering response. Must be the air in here.
Great post by Andrew. Long-term monitoring probably shouldn't be necessary--you should be able measure RH% and perhaps CO2 for a short period or two, determine how much ventilation is needed, implement said ventilation using a reliable strategy, and then put the equipment away. I own a handful of nice IAQ meters and only needed to use them in my own house for a short time before understanding the ventilation requirements.
If you can find a way to use RH% or CO2 to control your ventilation equipment, that would be a nice upgrade. I might move to that at some point, instead of using a timer. I think a lot of houses could benefit from a system that does not require the occupants to pay attention.
If the problem is that you lay awake worrying that you might have bad IAQ, then monitoring may be a complete solution. If the problem is actually bad IAQ, then monitoring could be a very useful step in solving the problem. Identifying which aspect of IAQ is a problem, and quantifying it, dictates what the remaining steps are. Sometimes you can solve it by eliminating the source of the contaminant. Some contaminants can be effectively filtered. If the source of the contaminants is too many people breathing in your house, then increased ventilation is probably the best solution (depending on how much you like those people).
I'm one of those who asked about "toxic" houses and it sounds like monitoring is no solution. It may make you aware of the patterns in the house, but it's not really helping to solve anything.
After asking that question, I kind of went crazy - I got a CO2 monitor, CO meter, and 8 of those Accurite temp/humidity gauges. However, this was also after I discovered my water heater has been backdrafting for a while (only when the bathroom fan is on which would mean every single morning).
And what have I learned? Just the patterns. Nothing actionable. My CO2 numbers are regularly 1100ppm+ in the house and for some reason spike to 1600-1700ppm overnight. One day I accidentally left my bathroom fan running for 24 hours (a 60cfm fan) after going to a friend's house and came home to a 400ppm reading. While comforting that my house can reach outside levels, that number quickly replenished itself to 900ppm within a couple hours (2 people).
Another pattern...my wife can be home for several hours & the CO2 floats around 7-800ppm. Once I get home, it's like it shoots up - does this mean I'm just a big 'ol walking CO2 balloon? I have no idea.
So my analysis is that even with monitoring, unless it's something you can act on, all you're really doing is making yourself go crazy with the specific numbers. I will say that with the CO2 and CO monitors that I got, the biggest actionable output came when seeing how much the numbers rise when the (gas) stove is on. CO pumps out in the hundreds of ppm when it first turns on and reduced to double digits after warmup, but CO2 easily reached 2500ppm. And this is with the window open but no fan running.
Even still, is this really helping to prevent a sick/toxic home? Who knows. My home was measured to be 0.2 nAch.
Response to J Pritzen -
If you know that you are backdrafting your water heater, I would suggest that is probably actionable. The high-ish CO2 numbers indicate that you could probably use some sort of improved ventilation. I suspect, based on my experience, that the overnight spikes are due to lack of air distribution/movement. When you get up and have activity within the house, and when the forced air (?) system comes on, the high localized CO2 readings are reduced as the air is diluted throughout the house.
Gas stoves/ranges are a somewhat different matter, which may be okay if you have adequate kitchen exhaust system and if you use it whenever the stove is on...although many kitchen exhaust fans are stronger than bath vents, so you may be backdrafting your water heater again. I'd suggest reading Martin Holladay's article here on GBA entitled Makeup Air for Range Hoods.
Good luck,
Thanks all for your input. I am getting to the final stages of building a house that I have attempted to make super well sealed and insulated. I have tried to keep nasty offgassing building materials out but some engineered timber did get used in a weaker moment. There is no central HVAC system but one pair of lunos HRVs that I was assured would be sufficient and I would have no need for either bath or range ventilation. It is a tiny house (650sq ft). I spent ages in trying to figure out the best/correct ventilation system, but I don't feel overly confident that I have succeeded. My idea behind monitoring air quality is to do something about it if it is a problem (more ventilation, get rid of gas stove, etc) whether CO2 or anything else I should be concerned about, particularly as I am still trying to avoid using an electric cook top as I sooooo prefer cooking on gas.
I have read the articles suggested above and appreciate the input. It seems like finding a decent CO2 meter and trying to keep as much nasty offgassing material out of the house as I can is a reasonable solution. An ideal solution would be a ventilation system that was controlled by CO2 levels. Does anything like that exist? Probably too late for me now, but I am curious.
An induction cooktop works better than gas. Faster, uses less energy, more control, much easier to keep clean. Try a cheap induction burner ($50 from Amazon) before you install gas. If you like it, get an induction cooktop. We love to cook (always cooked with gas) and are thrilled with our induction cooktop.
The kitchen lunos is on the wall behind the stove (but not just above it) and the second unit is in the bathroom, thus they were suppose to do the job. Like I said, I was skeptical but threw up my hands when I started trying to figure out supply air, heat loss, and such if I added more extraction. I am OK on the codes.
I think you're going to want at least ~100 CFM of exhaust right at the cooktop. What are your Lunos units rated to move? Regardless of fuel, cooking creates a lot of humidity and airborne particulates, and you want them removed effectively. I'm skeptical of anything but a range hood that's directly over the cooking surface.
A Lange wrote: "I would have no need for either bath or range ventilation"
From a certain perspective i can understand why your consultant assured you that the Lunos would be sufficient, but a central ventilation system has very different aims from bath and kitchen exhaust fans. Bath fans are for dissipating odors and excess humidity. Kitchen exhaust is to remove contaminants generated by cooking. Trying to do these functions from a location in the house removed from their source is both ineffective and may help spread the things you are trying to remove into the rest of the dwelling.
It's also probably worth running your plan by your building inspector as most building codes require both designated kitchen and bath fans.
Your doctor would not prescribe without determining your condition. And we don't want to waste a single dollar on a needless pursuit or "solution". The value of monitoring is to determine exactly what we are trying to fix, and then to measure that fix to see if it worked. Otherwise, you go back to the dark ages, waste money throwing dollars at the problem and "guessing".
As to CO, there was a pioneer building scientist that said something like, "If there is a pile of crap in the middle of the floor, don't ventilate. Get rid of the pile of crap". There are many benefits to induction. Induction is far more responsive than gas, it's more efficient because most of the heat does not go around the cooking utensil and up, you can't burn yourself with it and it does not supply your home with large amounts of Carbon Monoxide.
Having a kitchen hood that captures well is critical. Most people cook on the hottest burner, which is often on the front. Unfortunately, most hoods cannot capture much of the CO, steam and odors from this front, corner location. Having a hood that is grossly overpowered often removes ambient air without extracting the problem air if it escapes. This is why we usually install a next-size-up hood that is wider, extends out further and runs quietly so that people are not offended by the noise and they will actually use it (at a lower, quieter fan speed).
And the Lunos that was mentioned is a pair that switches back and forth, alternating as intake fans, and exhaust fans. So if placed in a bathroom or kitchen for spot ventilation, they will take turns removing offensive conditions and spreading them throughout your home.
Our homes are very dynamic and full of self-inflicted wounds to comfort, health and efficiency often made worse by a rush to further guessing. In short, monitors help by letting us understand what is happening; and then they help by letting us know the results of our efforts to insure we make things better instead of worse.
Be safe.
Thanks Don, Your point is sort of where I started from, wanting to measure what, if any, problem I had and then try to fix it instead of guess what I might need and making an expensive mess of it. Assuming I am willing to start living in the house as is and then adjust to actual needs for indoor air quality, is the general consensus that measuring CO2 is sufficient or should I be measuring something else?
As for induction cooktops, I tried the idea of buying a single burner to test it out and it was horrible! I think I may have gotten a bad one, but it was ubber-hot even on low setting (boiled water) and didn't work with many of my steel pots. Considering it takes me almost a year to go through a 45kg LPG gas bottle for both water heating and cooking, it is hard to argue for induction based on energy use, although I do agree that having an unvented open flame is not ideal.
@ A Lange
I would be interested in the layout for your tiny house, i live in a similar sized house which was haphazardly designed and i would be very interested in seeing how it could be done better.
This thread got me thinking about controlling my Honeywell HRV with a CO2 meter, or perhaps a combined CO2 and VOC meter. Conceivably I could kick the HRV into high speed upon a call for additional air exchange, ostensibly saving energy other times. Unclear whether there would be enough savings to justify the meter purchase, I suspect not. However it would be nice to have some IAQ data as part of such a lash-up.
Anyone try one of these Tongdy units? http://www.co2meters.com/Documentation/Datasheets/DS-TON-0003.pdf Does both CO2 and VOC, which is of interest considering I have a gas stove and masonry heater. I have never heard of this company though.
How about the Honeywell units? http://www.honeywellanalytics.com/en/products/IAQPoint2 Seem to do either CO2 or VOC, but not both at the same time. Honeywell of course is a known player; the duct mount unit would work nicely in the sheet metal "return" manifold that feeds "stale" air to my HRV.
Alan B, Happy to share, but maybe best done off of this forum. Do you have an email I should use? Or is there a method already in place here to be able to communicate directly that I am not aware of?
Andrew B, Looking forward to hearing what people recommend for monitors.
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