Attic mold is a common problem in the Pacific Northwest and beyond. Addressing any attic mold is the best way to ensure it doesn’t spread or affect the health of your family.

What Causes Attic Mold?

Attic mold is almost always the result of high humidity in the attic space. This high humidity causes condensation on the cold portions of the roofing materials (plywood or OSB) and results in mold growth on these surfaces. Attics should be designed with proper ventilation in mind. This would usually include low vents (soffit vents, bird blocks, etc.) and high vents (roof vents, ridge cap vents, etc.). Current code in Washington state requires one square foot of ventilation per 300 square feet of attic footprint. This is a general rule, but a qualified inspector should evaluate the type, location, and airflow through the individual vents to determine exactly what has caused the deficiency that led to the attic mold growth. A neutral unbiased attic mold inspection will give you the information you need to find out exactly what the next step should be.


Where Does the Humidity Come From?

The humidity that builds up in your attic may come from several places:

  • Moisture generated by occupancy (cooking, cleaning, bathing, and even breathing)
  • Bathroom or kitchen exhaust fans that aren’t fully ducted to the exterior
  • Gaps and penetrations between the living space and the attic space
  • Roof leaks


What Does an Attic Mold Inspection Include?

Before attic mold remediation is even considered, the source of the moisture should be identified and documented and a plan to resolve the underlying conditions should be made. Only a qualified professional with experience in building science and building diagnostics can do this.

A thorough attic mold inspection should include:

  • Climbing into all accessible areas of the attic
  • Moisture testing of a representative area of sheathing and framing
  • Inspection and documentation of ventilation type, location, and size
  • Assessment of the extent of damage
  • Assessment of exhaust fan ducting
  • Assessment of HVAC ducting in the attic
  • Inspection of insulation
  • Inspection of the seal between the living space and the attic
  • Evaluation of the humidity levels and ventilation in the living space

Evaluation of all of these factors should be documented in your report. The inspector will likely provide a floorplan and several digital photos along with the general narrative.


Is Attic Mold a Health Concern?

Typically, air from the living space rises up and into the attic, and in most cases mold spores from the attic do not pass back down into the living space. Attic mold is sometimes a health concern, but only your inspector can evaluate this, and it may require an air quality sample before the attic hatch is opened. Even if the mold is not causing a health concern, you should address it, as it may decrease the lifespan of your roof and decrease your home’s value.


How Is Attic Mold Cleaned Up?

Attic mold can be cleaned in a wide variety of ways. A neutral inspection will provide you with a list of options and the pros and cons of each. Your inspector can hep you decide what the most practical solution is for your mold issues, but here are a few of the common methods that may be referenced in your attic mold inspection:

  • No mold treatment is recommended:
    • The mold will not continue to grow, but active spores and visible mold will remain. The remaining mold spores are unlikely to impact the indoor air quality, but this is likely to have a negative impact on the home’s resale value.
  • Treat mold growth with simple antimicrobial spray:

    • All mold growth and spores will be killed and deactivated. Significant residual staining will remain, and this may cause concerns when selling the home.
  • Treat mold growth with antimicrobial spray and pigmented encapsulant:
    • This process will kill all mold growth and leave a white pigmented seal on all sheathing and associated framing. The mold growth will be completely resolved and the attic will look clean, but evidence of treatment will be obvious (please discuss warranty and documentation in regards to this service with your contractor).
  • Remove all mold growth via sanding, grinding, or dry-ice blasting:
    • This process will require complete removal and replacement of all insulation. The final product should be naturally colored wood sheathing with no residual staining (please ensure that your contractor will guarantee no residual staining).

If you suspect that your attic has mold growth, contact us today for an attic mold inspection.


Comments are closed.