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Creating positive pressure to combat allergies

HU-828618346
9 months ago

Background

I am extremely sensitive to ragweed pollens and I suffer during summer and fall every year. [1]

I already have 10 air purifiers spread out around my 2400sq ft house, and while my symptoms are much better indoors vs outdoors, I still experience symptoms indoors. [2]


Hypothesis

An article I read [3] suggests that air purifiers may help in reducing PM2.5 around 75% vs the outdoors but to achieve 100%, a positive air pressure is necessary indoors. The 75% reduction tracks with my experience.

Though my home is new (2015 built) and well insulated, I think outside air is entering my house for a variety of reasons:

  • This is normal - I think studies say between 30% and 150% of the air in the building gets replaced with outside air over an hour
  • Pressure differential between inside the home and outside due to heat (it goes up to 110F in the summer) or wind brings in air
  • I have 6 exhaust fans in my house (kitchen, laundry, 4 bathrooms). Each bathroom’s exhaust fan pushes out 80CFM. If all exhausts are running, I might be exhausting 500 CFM out of my house, which needs to get replaced somehow.

Question

I believe that my issues with allergies indoors can be solved by creating a slight “Positive Pressure” inside my home to prevent polluted air from entering through my building envelope. I have no background with HVAC systems however and need help to figure out what system I need.

  • What systems could you recommend to help create positive pressure in my house? I’m imagining something like somehow pumping in air into my house (after filtering the outside air with a HEPA filter, of course). This is similar to what was done in the article or how Tesla’s Bioweapon Defense Mode works in their cars[4]
  • How can this positive pressure intake adapt as I turn on/off some of the exhaust fans in the house? If I pump in too much air, it might increase my heating/cooling bill, but if I pump in too little, it might not be enough to compensate for the exhaust
  • Is it possible to modify my exhaust fans to compensate for the air loss by also bringing in air via something like an ERV?


Additional details

[1] I’m positive this is seasonal allergies and not mold or any other issues. I live in the Sacramento Valley region which is known for really bad ragweed allergies. The severity of my symptoms correlate with local ragweed pollen counts and with symptoms of friends. I also feel much worse outdoors than indoors. I also feel worse without air purifiers indoors. Whenever I leave the region, my symptoms go away completely. I have gone to multiple allergists, tried a variety of allergy medications/sprays, allergy shots, etc, and while things gave some relief, I still don’t feel normal. I think my best bet is improving indoor air quality.

[2] One reason I know that my air purifiers are not perfect is that during wild fire season, I still smell a significant amount of smoke inside (both via smell and higher air particulate counts). The air purifier helps a lot, but the effect is maybe a 75% reduction like that AirGradient article above stated.

[3] https://www.airgradient.com/blog/air-purifier-vs-positive-pressure-fresh-air-system-an-unfair-battle/

[4] https://www.notateslaapp.com/tesla-reference/1273/tesla-bioweapon-defense-mode-what-it-is-and-how-it-works

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