Crawlspace Mold, Ventilation and Insulation

Crawlspace Mold, Ventilation and Insulation is the last of my Crawlspace Inspection posts and I'll take care of the items 9 & 10 from my Top 10 list. They are somewhat correlated, at least partially.


Crawlspace mold / Crawlspace Ventilation / Crawlspace Insulation

Let’s wrap it up – Crawlspace Mold, Ventilation and Insulation is the last of my Crawlspace Inspection posts and I’ll take care of the items 9 & 10 from my Top 10 list. They are somewhat correlated, at least partially.

Top TEN Crawlspace Problems:
1. Cracked foundation / possible structural problems
2. Leaking foundation
3. Drainage problems / flooding crawlspace
4. Plumbing components issues – leaking water supply lines, drain pipes, crawlspace water heater installation problems
5. Heating system issues
6. Electrical components issues
7. Floor framing and structure support issues
8. Structural pest infestation – those are Termites, Powder Post Beetle, and Carpenter Ants
9. Mold problems
10. Crawlspace ventilation and insulation

Crawlspace Mold Problems

Crawlspace mold on floor framing 2Crawlspace mold on floor structure caused by leaking plumbingCrawlspace mold on the floor framing 2Crawlspace mold on floor joists caused by leakage from exteriorCrawlspace mold, as many other problems described in previous sections of the crawlspace inspection tutorial, is strictly related to moisture presence. Because mold grows on pretty much anything and often takes different shapes and colors, you can expect to find crawlspace mold on pretty much every possible surface.

So look everywhere for crawlspace mold and pay special attention to areas along the foundation and under the bathrooms, kitchens, utility rooms containing water heaters, furnaces, and / or washers – any place that water leakage / moisture penetration might occur.

Crawlspace mold on main beam supporting columnIf you have a chronic moisture problem, maybe related to poor drainage around the house or a high water table (level of groundwater), the crawlspace mold might appear on the floor, walls, supporting columns and entire framing. If you notice discoloration or unusual residue / substance on any of the surfaces, have it tested by a professional. Unfortunately this is the only way to find out what it is and if it is confirmed to be crawlspace mold, determine if it is toxic.

Crawlspace mold and Crawlspace ventilation

Crawlspace mold - one of the ways to prevent mold from growing in your crawlspace is to provide correct ventilationProper ventilation of the crawlspace is crucial for a healthy house and to prevent crawlspace mold growth… well … not necessarily, or should I say – the science decided that not any more. As it often happens with some beliefs, new scientific developments change them to the complete opposite. However, the installation of 1 square foot of venting per 150 square feet of under-floor / crawlspace area is still a code requirement.

For our crawlspace mold / crawlspace ventilation inspection purpose:

Crawlspace mold / crawlspace ventilation - vents leaking water (exterior view), installed below the ground levelCrawlspace mold / crawlspace ventilation - vents leaking water to interior, installed below the ground levelIf you have any fuel burning appliances installed in the crawlspace area, you’ll need so called make-up air / combustion air, which is necessary for a proper / clean burning process. Unless those appliances have a sealed combustion chamber and use exterior air for combustion (most high efficiency furnaces do, but not all of them), you might need an air vent installed in the crawlspace area. If you’re not sure, have a licensed HVAC contractor check it for you

  • If you have a dry crawlspace, you are lucky! Your vents are most likely adequate (or you might not even have them at all) and there’s most likely no crawlspace mold presence (unless caused by plumbing leaks) – I personally wouldn’t touch it
  • Check areas around the foundation vents to ensure, that there’s no leakage – vents usually leak because they’re below the ground level on exterior, and you might need a small window well
  • For wet crawlspaces (leaking foundation, high water table, malfunctioning or missing drainage system) – once again: try to eliminate the source of moisture before it causes crawlspace mold growth, and read Venting or not – the Crawlspace dilemma (link below).

The crawlspace ventilation topic is quite large and there are a few scenarios and various options to consider. Therefore I’ll do my best to wrap it up and explain current scientific point of view in Crawlspace Venting or not…

Crawlspace mold / Crawlspace insulation

The crawlspace insulation improperly installed with exposed paper facing which is flammable and should be facing the warm part of the house (floor) or be covered with gypsum board other code approved materialsWarning message on the crawlspace insulation vapor retarder paper - highly flammable, and should never be left exposedCrawlspace mold / crawlspace insulation - loose, hanging batt insulation on the crawlspace ceilingDepending on the type of crawlspace you have under the house – above the ground, partially above the ground, below the ground level – you might have insulation installed or not.

If it’s there, and if it is a blanket type with a paper facing (also called “batt” insulation) installed on the crawlspace ceiling / your floor framing, remember that the paper (moisture barrier) has to be facing the warm side of the house. It is highly flammable, and leaving it exposed creates a fire hazard.

Another problem to watch for in humid / wet crawlspaces is possibility of crawlspace mold growing on insulation sheets, sometimes between the floor an insulation layer.

It is easier to install blankets between the floor joists by securing paper flaps along the edges, but without fire-rated material on top of such installation … you know, accidents happen. You might also have: the spray-on type of insulation on the foundation walls, Styrofoam sheets, aluminum foil faced blankets (this one conducts electricity, so be careful if it is in contact with electrical components in your crawlspace), or some other materials – secure them if they fall off / separate from the surface they were attached to.

That covers basics of crawlspace mold, crawlspace ventilation and crawlspace insulation.

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