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Comment by gregwebs | Hacker News Reader

It is becoming a big topic because more people are becoming sensitive to mold exposure and more time is being spent indoors. Think of how the prevalence of allergies has increased dramatically in our society. Something similar may be happening with mold except at orders of magnitude lower prevalence. Actually there are theories that similar pathways are involved with allergies and mold- that mold triggers immune reactions just like allergies.

When I learned about mold sensitivity I got concerned and started doing mold tests and looking out for mold exposure but eventually realized that nobody in my family is mold sensitive. The "not a big deal" attitude is right for most people, but we should be sensitive to those that are highly mold sensitive.

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Exposure to mold is also likely to be correlated with socioeconomic status, especially in more humid parts of the country. Think what kind of people are most likely to live in rundown houses (or even basements!) barely above the water table, without a functioning HVAC unit.

Mold is the kind of problem that is at most a nuisance for people who have the means to do something about it, but seemingly unsolvable for people who actually need a solution.

This! One of the best solutions to prevent mold is to improve energy efficiency. There are an increasing number of grant programs and Housing improvement initiatives available, but still those improvements are out of reach for a lot of people. We live in the Southeast US which is incredibly humid and so many houses have issues.

My sensitivity appeared to change after living in a moldy apartment. I originally scoffed that mold was an overhyped problem, but it caused problems for me that persist years later. I am now very sensitive to damp/moldy air and have to take an allergy pill everyday for indoor allergies.

Yes, time spent indoors, and the West's obsession with anti-septic environments. I bought a little cabin on a lake in NJ after moving from NY. I didn't bother sealing every crack and nook with sealant given my energy bill was reasonable, and I liked the fresh air exchange over time. Friends moved up there and built air-tight houses with all the modern materials with foams, glues, carpet backing, tiling and other products that need a significant time to off gas, trap particulate and moisture, and as we now know, mold can thrive on almost anything with moisture. Anecdotal, but it seemed they were at the doctor's office 2 to 3x per year vs. my kids only going for checkups. People are now hypersensitive to so many things, and I believe a lot is due to this approach to what it means have a healthy home and household. I have raised 4 children, and aside from some mildly annoying hayfever for a very short period for 2 of them, they are mostly non-allergic and I am grateful, have no medicinal allergies. I also think we have grown a bit hypochondriacal and have actually fed into this phenomenon. There are even studies claiming 50% more likelihood to contract MS if you are exposed to the solvents or chemicals in paint thinners and household cleaning solutions. Even "organic" products in large amounts do not bode well for most people's health, so housing construction that claims to be "organic" with low VOC elements used sometimes doesn't even address the need for sufficient air exchange with fresh air over environmental ratings on windows, appliances, etc. Somewhere in the middle there is a happy medium from my natural materials, drafty cabin, and an air-tight, "organic" material house. We had mold in the attic and it was black and after reading about it back in the late 90s early 2000s I went up and cleaned the rafters with Clorox (yes, chlorine, I know. My nuclear solution!). and opened the once-closed off ceiling to the attic. I put in skylights and opened up the A-frame for more air and light. Nobody in my family at the time, including my newborns seems to have suffered from having lived with this black mold, but evidently, there are many and I am not sure how prevalent dangerous black mold is from your generic black mold, but as I have said earlier, anything in too large a quantity can be deleterious to your health. Too much grain dust in the air would irritate you too and in high enough concentrations probably kill you over time!

Houses are a lot tighter than they were in the past which makes it harder for them to "dry out" unless you have some kind of air circulation system. My house certainly doesn't and it wouldn't be easy to retrofit.

I don't know about that. Most new houses have air conditions for the hot humid days and a heater for the cold days. Most fully below grade basements have dehumidifiers in wet climates. I've never had issues with moisture except in cases of some system failure, like a sump pump.

Apartments in our block have air-tight windows and doors. But also there are passive ventilation input in every room, which allow flow of some fresh air through closed windows. Central ventilation is constantly taking air from the apartment so we have no issues with excess moisture. Some people even put a humidifier during cold months to get moisture level up to 50%.

In cold weather, I think 35-40% RH is a good target, but where lower is okay and higher is not. There’s too much chance INO for that warm, humid air to migrate to the cold outer wall and drive condensation.

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