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Mold in the basement

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Basement Mold - General Information

Suffering from a wide variety of ills, basements are common sources of musty odors and occasionally, mold growth.  This occurs because basements often lack sufficient ventilation, allowing stale, moist air to accumulate.  Compounding the problem, basements are often unheated or under heated, causing the relative humidity to increase. 

Is basement mold a health problem?

Due to the poor ventilation and air flow typically found in basements, mold growth in a basement can be a greater health issue than other areas of the home.  Also, due to the stack effect, mold contaminated air from the basement will often infiltrate the upper portions of the home.  

The potential for basement mold to cause health effects depends much on the building materials used on the flooring and walls.  For example, an unfinished basement with bare concrete walls and flooring, will provide far fewer food sources for the mold.  However, a finished basement with insulation, sheet rock and carpeting provides dramatically more food sources.  Cleanup and removal of basement mold also grows increasingly complicated and expensive as the quantity of materials increases.

What are the most common mold, moisture and IAQ issues in basements?

What steps are necessary to prevent mold growth from occurring in a basement?

Moisture management and ventilation are the two key factors for creating a mold free basement. More specifically, your goal is to create a warm and dry environment.  First, we'll tackle the moisture issues.  These fall into two broad categories, airborne moisture and liquid moisture.  

Liquid moisture includes issues such as:

  • Water from entering through the cold joint
  • Flooding from periodic high water events
  • Leaky foundation walls
  • Water infiltration through cracks in the concrete slab

Airborne moisture includes:

  • Excessive relative humidity
  • Vapor emissions through the concrete slab

How are basement mold issues remedied?

The first step in addressing any mold issue is to prevent excessive moisture entry or accumulation.  This may require fairly costly efforts, such as installing french drains, interior footing drains or a sump pump.  These are required when liquid water is entering from an exterior source.  However, if the source of moisture is internal, such as from poor ventilation and occupant activity, the solution is often much simpler.  These include: Increasing the air temperature, increasing the quantity of fresh air drawn in from the exterior and properly exhausting interior sources of moisture generation.

Recent Inspection Report Involving Basement Mold

Work #: 201015

Reason for inspection:

  • Tenants in home have found  mold growth in the bedroom and requested an inspection to determine the source and the solution.

Summary of concerns:

  • Elevated relative humidity in the basement has led to condensation based mold growth inside a closet and along several places of the exterior bedroom walls.
  • No ventilation fan in the on-suite bathroom allows for excessive relative humidity to be introduced into the bedroom.
  • Evidence of a previous water intrusion event was present around the perimeter of the basement bonus room.
  • Water damage noted in the ceiling of the hot water tank closet in basement.  This appears to be a result of a previous leak from a bathtub.

Summary of recommendations:

  • Recommend remediation of visible mold growth according to standard remediation procedures.
  • Recommend removal of bottom 2 ft of sheetrock from around basement bonus room and laundry room.
  • Recommend removal of water damaged sheetrock from ceiling of hot water tank closet in basement according to standard remediation procedures.

PROPERTY DESCRIPTION:

  • Two story, mid 1970's home with daylight basement.

VENTILATION:

Adequate Ventilation Present Adequate Ventilation Not Present

Recommended ventilation of residential homes should be between 0.35 and 0.7 air changes per hour (ACH).

Desired Ventilation Rate:  .35 ACH (Air Changes per Hour)

Square Footage:            750 sq/ft    Each Floor

Average Ceiling Height:   8 ft    X

Required Ventilation:      35.00 continuous cfm per Floor

Recommendations:

  • Basement bathroom does not contain a ventilation fan. 
  • Recommend installing a Panasonic Whisper Green® ventilation fan in bathroom to assist in evacuating the relative humidity from inside the building.  Whisper Green ventilation fans operate consistently at a low volume (35 cfm) and automatically ramp up to a higher volume (80 cfm) when a motion sensor is activated. An integrated timer will maintain the higher volume for a set period of time and then return the fan to the lower operating level until activated again.
  • Ventilation fan in upstairs bathroom is present but is noisy and inefficient at removing relative humidity from inside the room.  

LOCATION: Basement Bedroom

Summary:        Abnormal Conditions Found!

Observations:

  • Moderate to heavy amounts of visible mold growth were found inside bedroom closet. 
  • No increased moisture content noted in building materials inside closet or along wall upper or lower sections of wall.  This indicates that the mold growth is likely due to elevated relative humidity levels inside the home and not a failure of the building envelope or plumbing system(s).
  • No suspicious temperature differentials found with thermal imaging.
  • No obvious signs of water damage noted.
  • Main water supply line comes into home inside bottom of closet.  Supply line was not insulated and condensation was noted on the pipe at the time of inspection.
  • Some minor visible mold growth was noted along window frames and on the window sill.  A blind was present in the window and was closed at the time of inspection.  This traps moisture laden air against the window which results in condensation.  Condensation is the source of the moisture that lead to the mold growth.
  • No elevated moisture levels found in carpeting or along base of walls. 
  • RH:58 % Temp: 63°F CO2: 575 ppm CO: 0 ppm

Recommendations:

  • Recommend removing the sheetrock of exterior walls in closet. 
  • Recommend insulating exposed supply line pipe to minimize condensation.
  • Recommend insulating exterior walls to prevent condensation.
  • Recommend building a box over supply line running along top of closet and install spray foam insulation over top to prevent condensation.
  • Recommend cleaning remaining areas of visible mold growth in bedroom with an EPA registered biocide and encapsulate with a latex based antimicrobial sealer. 

LOCATION: On-Suite Bathroom

Summary:        Abnormal Conditions Found!

  • No ventilation fan present in bathroom. 
  • No increased moisture content noted in building materials.
  • No suspicious temperature differentials found with thermal imaging.
  • No obvious signs of water damage noted.
  • Minor amounts of visible mold growth noted on walls and ceiling due to elevated relative humidity levels and no ventilation.
  • RH:56 % Temp: 65°F CO2: 597 ppm CO: 0 ppm

Recommendations:

  • Recommend installing a Panasonic Whisper Green® ventilation fan in bathroom to assist in evacuating the relative humidity from inside the building.  Whisper Green ventilation fans operate consistently at a low volume (35 cfm) and automatically ramp up to a higher volume (80 cfm) when a motion sensor is activated. An integrated timer will maintain the higher volume for a set period of time and then return the fan to the lower operating level until activated again.

LOCATION: Hot Water Tank Closet

Summary:        Abnormal Conditions Found!

  • Significant water staining present on unfinished sheetrock ceiling.
  • No increased moisture content noted in building materials.
  • Silicone had been applied around exposed ABS drain pipes.
  • Ceiling sheetrock is significant water damaged and should be removed.
  • No significant mold growth observed.

Recommendations:

  • Recommend removal of ceiling sheetrock from closet. 
  • Remove any remaining three-dimensional mold growth from all exposed areas via HEPA vacuum, wire brush and/or hand sanding.
  • Treat all exposed areas with an antimicrobial biocide and encapsulant.

LOCATION: Basement Bonus Room

Summary:        Abnormal Conditions Found!

Observations:

  • Lower edge of sheetrock was examined and was found to have evidence of exposure to moisture at some point. 
  • No increased moisture content noted in any areas of sheetrock sampled.
  • No suspicious temperature differentials found with thermal imaging.
  • Sections were present where sheetrock edges were found to be crumbling due to exposure to moisture.
  • Some mold growth was noted on the back side of the crumbled pieces of sheetrock. 
  • No visible mold growth was found to be on the surface of any walls, under carpets or carpet pads. 
  • Moisture appears to have originated from the laundry room and spread out into the bonus room. 
  • It is unlikely that the existing mold and water damage is contributing to any indoor air quality concerns at this time.  If however, any sheetrock is removed, it could potentially expose the room to elevated levels of mold spores.
  • RH:53 % Temp: 63°F CO2: 563 ppm CO: 0 ppm

Recommendations:

  • It is recommended that the bottom two feet of sheetrock be removed from around the perimeter of the bonus room and the laundry room to ensure all water damage and mold growth has been effectively removed.  If evidence of mold growth extends beyond 2 feet up the walls, client should remove and additional two feet at that time. 
  • All removal work should be conducted according to standard remediation procedures such as full containment, negative pressure, HEPA air filtration and the use of appropriate personal protective equipment.

LOCATION: Upstairs Dining Room

Summary:        Abnormal Conditions Found!

  • Minor rust staining on back side of carpets and on the tips of the carpet tack nails.
  • No increased moisture content noted in building materials.
  • Minor crumbling noted on lower edge of sheetrock.
  • No water damage noted on subfloor.
  • No significant mold growth observed.
  • Carpet tack strips in entry closet appear clean and free of staining.
  • Opposite side of wall (Kitchen eating area) did not show any signs of staining or water damage.
  • It is the inspectors opinion that a small, isolated moisture event occurred at some point previously.  There does not appear to be any evidence of significant remaining damage at this point. 

Recommendations:

  • None
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