If you break out in a rash and require showering and anti-histamines every time you enter the basement, that's a pretty severe problem.
Last year when this started--in the apartment I've been living in until last week--I started breaking out in a rash one day so bad I couldn't sleep. It itched and I had bumps and inflammation and redness EVERYWHERE (like 95% of my skin surface), I thought it was fleas or chiggers or hoards of invisible mosquitoes or something. The problem has declined sharply since I moved out. I may have suddenly developed a sensitivity after living in that apartment for several years.
If you're simply planning to vacuum dry mold spores, you'll probably make the problem worse as you will be getting them airborne.
Valid point. Vacuuming the dust and cobwebs out of the joists is probably a good idea in any case, though scattering dust into the air isn't a great prospect. Mold or not, dust contains things like dust mite bodies/feces, insect feces, human feces, human skin, dandruff, mold spores--even if your house doesn't have visible mold--and God knows what else.
The point of a filtered vacuum cleaner is a "Sealed HEPA" is "sealed" because 100% of the air necessarily passes through the filter, rather than bypassing a loosely fitted filter. Still has to be MERV 7 or higher (MERV 5 passes mold fragments and spores) and even then, it's like 50%-70% filtration per pass--half that crap goes into the air.
On the other hand, I could just vent all that crap to the outside
, and by now I think you can agree that's a good idea (and under a $1000 add-on).
Is this one of the "bargain" properties you've been looking at recently?
Yeah it's a lower cost property, it's in pretty good shape--the construction and remodeling jobs are surprisingly well-done. Very basic--painted firewall (cement walls on 2 sides), carpet, laminate tile--but the floors and roof are constructed properly (subfloor is even plywood) and there are no structural issues.
Anything with visible mold (dry wall, etc) needs to be torn out. I imagine that the basement would be emptied, sealed, power-washed with bleach or something and then dried.
The only live mold present (found via inspection I paid $350 for) is on a small stretch of concrete wall right at the foundation, due to water inlet in that immediate area. Anything else present is spore. Nothing is growing on wood or in drywall. Hence the dehumidification of the basement and the need for a MERV 13 filter in the furnace ASAP--to prevent mold growth and to contain the mold spores.
Correcting the downspout outside eliminates 90% of the problem; correcting the grade by itself eliminates around 75% of the problem (most water would run away); sealing the foundation (paint with sealer) corrects much of the problem, but the sealer will fail if the other measures aren't taken. With the problem corrected, I still need to remove the mold and spore.
None of the subfloor (visible from the basement) or joists show growing mold. The drywall is all new, carpet is new, the entire upstairs is safe and clean and mold-free. I'll be taking up the floor, building up the subfloor, and laying tile and hardwood flooring, so I'll get a pretty good look at that and have easy opportunity to replace anything there. Taking up the carpet in the upstairs and doing the same, with the front room being the most fun--it's half above the porch, so the joists slope down by design; I'll sister new joists so I have a fully level floor, add insulation above the porch (there's NEVER insulation in the floor), then lay brand new subfloor in that entire room, then unfinished hardwood, then polyurethane finish. Yes I planned this.
(That power unit is WAY oversized for the house--they all are--but that's the smallest I'll get because I can't get a smaller true cyclonic unit. Bagged units QUICKLY lose power because particulate lines the inside of the bag and clogs the pores, impeding vacuum flow. This is true of all vacuum cleaners--HEPA filters clog, bagged canister vacs clog, a cyclonic system keeps its power even when full. Bagged units also occasionally experience bags bursting and, without a dedicated bypass design, this will immediately destroy the unit; most decent units have a dedicated bypass, some cheap ones cool the motor with filtered vacuum air and thus when a bag bursts they're permanently destroyed.)