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Air Quality

Today I learned how to better control our indoor air quality by controlling the air up under the house.

I started sneezing about a month ago and It's happened to me a couple of times of the last several years. I've never had allergies that I'm aware of but it seems to be right about what I like to call 'mushroom season' because there are lots of mushrooms1 growing in the yard. We even had some new ones this year most likely from the chipped mulch from the trees that came down during Helene2.

There has been plenty of rain and the air is still warm so on about day three of sneezing I went on a mission to see if I could fix it. I also blamed it on the amount of dust and other particles in the house from the renovations - drywall sanding, paint, and so on. I went after that with the shop vac and we've been swapping out the HVAC air filters and running separate air filters as well. I decided the first thing to do was to get an air quality monitor to measure.

I added a Wyze air purifier that wouldn't need another ecosystem app3. It's good - super quiet and super responsive with measurements. We've already got two other air purifiers running but this one is fascinating to watch it spike up when a candle is lit or something is on the stove. I'm now watching the air quality changes hourly. We recently re-insulated both attics and I wanted to inspect the duct work in the crawlspace4 as well.

Crawl Space​

Let me just quickly say I'm not a fan of attics or crawl spaces - it doesn't make any sense having spaces in your home that aren't monitored. Nor does it make any sense running your ducts and having equipment in an unconditioned space. I'm a big fan of mechanical rooms or basements where you can easily access your electrical, pipes, ducts, blowers and water heaters. The stack effect5, can suck air from the crawlspace into the home with falling temperatures because of a negative buoyancy force in the differing temperatures.

We recently added a gas tankless water heater in the crawlspace and I also needed to familiarize myself with the operation for maintenance. For my own reference, it's a Navien NPE-210A6 and requires a yearly flush. I mapped out the duct work in the crawlspace in the process.

And I added the coolest little thermal imaging camera7 so that I could check the duck work for leaks. It's amazing because it can see the temps behind walls so you can see electrical, leaks, ventilation, and drafts. the two upper red lines are hot water pipes and the lower blue line is the condenser for the air conditioning.

The duct work is in good shape and well wrapped with only minor temperature fluctuations at the joints. There were also some temp changes where the vents meet the flooring. The only other thing I noticed was the high humidity, which for this area is about par. The crawlspace is partially encapsulated and I say partially because it's lined 90%, but the outside vents are still able to open and are not capped. I never open them because the old adage about opening your vents isn't really up for debate anymore8. It's best to control the air in your crawlspace completely if you're able.

The humidity in our area can be brutal and it's particularly bad in August. I bought a Moiswell MP709 and set it up. It's got a built-in pump to push the water out from under the foundation. The first time I let it roll, it was almost 75% humidity under the house and I was able to drop it down to 60% in just under an hour. Moisture tests have always come back clean, but ideally it should stay between 45-55% just like your interior. I added a remote so that I can monitor and control the conditions in the crawlspace without actually having to crawl anywhere.

Now that I've got the August humidity under control, here comes winter with the heat sucking every bit of the moisture out of the house. We fight that too with humidifiers and houseplants. I'm gonna add some new gas fireplaces10 this year and I'll be using the direct vent versions because they don't affect the air quality.

Construction​

I've added this because the more I started monitoring our indoor air quality the more I learned. Although I started with a suspected seasonal allergies from humidity, I've now added VOCs from construction. We've been doing a renovation on our upstairs which involves pulling out ceilings, plumbing, and walls. There is a lot of sanding and sawdust generated. No amount of shop vac can clear it out. We're nearing the end of it with paint.

We've been running a couple air filter downstairs and letting a cross breeze clear the air upstairs. We've also had both of our attics re-insulated in the process. We're lucky that it' on a separate HVAC system but there are still serious air quality consequences from the construction. The most recent is an interesting in that when we fire up the stove downstairs, there is a smell of lighter fluid. Yes it's odd. First time was a bit of panic with the new gas lines in. Second time I was thinking what's wrong with the stove. Turns out it an effect caused by paint thinner. Odd part is that there's not enough paint thinner fumes left over to smell and it's only been the effect of the stove. Repainting three rooms and a lot of shelving means thinner and paint get spilled onto the sub-floor which seems to absorb it pretty well based on the stains.

The solution is a commercial grade air scrubber. I'm kinda ticked that our contractors didn't use one. I've spoken with the painters and carpenters about the air and they just said they get used to it. Our general contractor just suggested changing out the air vent filters regularly. Problem is those filters don't really handle VOCs11 or even some of the finer drywall dust. Nope - not having it. I apprenticed woodworking while in college we used a really nice ventilation and dust collection system. I've now rigged up a carbon air scrubber and I'm letting it run 24/7 for now. The temps and humidity will cool down enough next week to just let it air out naturally. With fresh carpet going in too, I'm gonna have the sub-floor replaced and I'll plan on running that scrubber until the construction air is gone.



Footnotes​

  1. notes / garden / mushrooms ↩

  2. notes / house / Hurrican Helene ↩

  3. Wyze Air Purifier - Apple Home enabled via Starling or Wyze Bridge ↩

  4. Crawl space - https://en.wikipedia.org/wiki/Crawl_space ↩

  5. Stack effect - https://en.wikipedia.org/wiki/Stack_effect ↩

  6. Navien NPE-210A manual ↩

  7. Topdon TC002 Thermal Imaging Camera ↩

  8. This Old House - Should Crawl-Space Vents Be Open or Closed? ↩

  9. Moiswell MP70 Dehumidifier ↩

  10. notes / house / fireplaces ↩

  11. VOC ( volatile organic compounds ) - https://en.wikipedia.org/wiki/Volatile_organic_compound ↩