TITLE
Problem Home Inspection - Southern Florida

TRIP DATE
November 6, 2002

INTRODUCTION

This home was built in February of 2002 and occupied in April. In June, homeowner noted soft spots in kitchen floor. The home was inspected in August. At that time, they found mold and moisture in the floor of the kitchen/dining area. No replacements were made. Homeowner reports that the belly was cut extensively.

Homeowner now reports moldy smell in Bath 2, warped kitchen/dining area, and a shift in the levelness of the bathtub in the master bathroom.

DESCRIPTION

The home is a 26' x 44' doublewide building with 3-bedrooms and 2 baths enclosing about 1,100 square feet of living space. No shading or landscaping was present.

The crawlspace skirting appears to be standard vinyl skirting. The ground around the skirting is damp though homeowners report that there hasn't been any rain for several days.

Homeowner reports the following operating conditions:

• 3 full time adult occupants
• 2 indoor dogs
• Thermostat is kept at 72° during the day and 74° at night (found at 70°)
• Bedroom doors are kept closed during the day.
• BR 2 and BR3 are closed at night. MBR is sometimes closed at night.
• Seldom run exhaust fans when not in room.

The ventilation air requirement is met with the use of an exhaust fan located in the utility room. Heating and cooling is accomplished with a central forced air system with the ducts located in the attic connected to a packed heating and cooling unit.

OBSERVATIONS (SEE PHOTOS)

• A visual inspection of the property and equipment revealed:
• Supply registers were not dirty and no condensation or water stains were present.
• The coil in the packaged unit was relatively clean.
• No mold or moisture was present at the marriage line ceiling joint.
• Sections of the kitchen floor were warped.
• Black mold growth was evident over the entire surface of the sub floor in the kitchen,
• The belly board was torn extensively near the supply and return duct entry points.
• A tear approximately 2' by 5' was present at the marriage line near the kitchen.
• No ground cover was present in the crawl space.
• Belly under hall bath had accumulated several gallons of water.
• Mold growth on exposed sub floor around dryer vent exit hole in floor of utility room (see moisture measurement table).

Temperature and relative humidity measurements suggest a significantly damp crawl space (see table) while a Delmhorst moisture meter showed high moisture levels in all floors manifesting mold. Significant moisture levels were also found in the utility room exterior wall and the shower portion of the hall bathroom plumbing wall.

Air Conditions
Location	Temperature	Relative Humidity
Outside	93°F	52%
Crawlspace	83°F	72%
Inside	75°F	46%

TESTING

Description

FSEC's testing protocol establishes the integrity of the building envelope and the duct system.  These tests assist in the determination of air-transported moisture that can cause severe damage to building components, increase energy consumption and decrease occupant comfort.  Three tests using a blower door and a duct blaster are performed. The first test employs the blower door and establishes a leakage rate for the house at a specific pressure (air changes per hour at 50 pascals (Pa) or ACH50). (250 Pa is equal to 1inwc or 6800 pa is equal to 1psi).  The next two tests use the duct blaster and yield the leakage rate of the duct system in a similar manner (cubic feet per minute of air leakage at 25 pascals (Pa) or CFM25). One test measures the total leakage from the duct system to the interior and exterior of the building (CFM25_total) and the second test measures leakage to the exterior of the building only (CFM25_out). For a duct system to be considered to be "essentially leak free", the CFM25_out must be a number that is less than 3% of the conditioned floor area (Percent Leakage = CFM25_out / conditioned area. X 100 >= 3%) or the CFMtotal must be less than 5% of the rated air handler flow.

The testing protocol continues with a series of pressure differential tests across the building envelope and various zones within the building as defined by interior doors.  The pressure differences are created by either normal operation of the building's HVAC equipment or the operation of the blower door test equipment.  Ideally, the pressure differentials created across the building envelope and bedroom doors should be close to neutral (below 2 Pa).

Blower door test and results

A blower door test was done to determine the airtightness of the building envelope.  A series of building pressures and associated airflows were recorded.  This provides the necessary inputs to determine the CFM50 and ACH50 of the house.

For reference, most new homes of today have an airtightness of approximately 0.75 to 1 CFM50 per square foot of floor area.  In this case, the house has an air tightness of about 0.80 CFM50/sqft.

Duct test

A duct system airtightness test was also completed.  A duct tester was attached to the air handler unit.  The supply registers were temporarily sealed off and the system was then depressurized to 25 pascals.  The total and outside leakage flow components were measured.  An airtight duct system would have zero leakage or both the CFM25_total and CFM25_out would be 0.  An "essentially leak free" duct would have a CFM25_out  >= 33* (CFM25_out / conditioned area. X 100 >= 3%).

Duct System Airtightness (Aug 12)

CFM25total  = 141

*CFM25out   = 71 (NOT essentially leak free)

Pressure diagnostic testing

Pressure differential measurements were completed to determine a magnitude and direction of flow across the envelope when the air handler fan operates. The effect of interior door closure on the main body of the home was also measured when the air handler fan operated.

Pressure Diagnostics w ith AHU (Note: the winds were moderate)
Condition	Pressure (main wrt out)
All fans off	+1.5 pa
AHU on	0 pa
AHU on & all interior doors closed	-3 pa

The pressure difference was also measured across each closed door when the air handler fan was operating (all supply registers were open and exhaust was off).

Conclusions

The problems with mold under the vinyl flooring throughout the house are primarily due to moisture intrusion from the exterior ambient environment, which enters (or tries to enter) the house by two distinct methods:

•         Diffusion through materials and/or

•         Air transport (driven by inadequate return air pathways) through various penetrations in the floor and wall interfaces.  These include dryer exhaust, electrical and plumbing penetrations and other cracks and connections.

Where does the moisture come from?

The ground is a source of moisture under all homes. A continuous vapor barrier ground cover prevents ground moisture from rising into the crawl space. Crawl space ventilation allows moist air to exit the crawl space to the outside. When neither is present, the warm moist air (see table of measurements) is trapped in the crawl space and enters the house by diffusion.

Bulk water, such as rain, can contribute to the moisture level in the crawl space. And in this home, a plumbing compromise in the hall bath introduced water into the belly (which held several gallons of water) creating a direct path for diffusion into the house.

Diffusion:

A vapor barrier or retarder, such as vinyl wall or floor coverings, can interrupt the diffusion process or water movement through a material.  If an interior vapor barrier (kitchen linoleum or vinyl wall covering) is at a temperature below the dewpoint temperature of the outside or crawlspace air and that air comes into contact with that surface, then condensation will most likely occur. The temperature of interior vapor barriers such as vinyl flooring and wall coverings can become even colder when cold air condition supply air is brought into contact with them. This may be the cause of the very wet east wall in the master bedroom where the diffuser was aimed primarily toward that wall, making it even colder than the surrounding air and accelerating condensation. The crawl space air is the suspected source of moisture involved in the diffusion process in the floors.

Air Transport:

The homeowners report operating the home with the interior doors closed a significant portion of time. A negative pressure of -3 pascals wrt outside was measured with interior doors closed indicating insufficient return air pathways from bedrooms, specifically the Master Bedroom which registered an unusually high +8.5 pascals wrt house. This consequential negative pressure in the main body of the house can induce infiltration of warm moist outside air.

RECOMMENDATIONS

NOTE: All plumbing repairs should be completed prior to implementing recommendations. All wet materials should be removed during plumbing repair.

HVAC:

• Sufficient return air pathways should be installed in all bedrooms.
• Inspect crawlspace ducts for condensation at the collars. Ensure collars are properly insulated.
• Encourage homeowners to set thermostats at 78 degrees or higher when in a cooling mode.

Crawlspace:

• If standing water is present or evident, identified the source and take steps to prevent future occurrence. Remove all standing water.
• The ventilation of the crawlspace should be increased to at least one square foot per fifty square feet of floor area. Lattice or brickwork is best with nearly 50% open area.
• A ground cover, such as 6-mil visqueen or plastic sheathing should be laid on the exposed soil.  This should cover at least 90% of the exposed area and should be installed and protected so as to preclude the possibility of water accumulating during heavy rainstorms. Joints should be lapped.
• Prevent roof run-off from entering crawlspace during heavy downpours. Rain Gutters will be very helpful as long as the run-off is directed well away from the home.

Floor assembly:

• All damaged, molded, and wet floor material should be replaced. Plywood decking is preferred. Any wet floor insulation should also be replaced.
• The floor cavity should be thoroughly dry and free of mold prior to replacement of floor assembly materials.
• The belly wrap should be 100% sealed with a material that will last the life of the building.  This will help prevent air-transported moisture from entering the floor assembly.

Address questions or comments to:
Dave Chasar - 321-638-1453, dchasar@fsec.ucf.edu
Or
Janet McIlvaine 321-638-1434, janet@fsec.ucf.edu

PICTURES

Skirting allowed limited ventilation of crawlspace. No ground cover present.	Vinyl flooring (kitchen) folded back to reveal extensive mold on subflooring and floor back.
Accumulated water draining from belly board under hall bath and kitchen due to plumbing leak. Crawl conditions: 83°F DB,    72% RH,    74°F DP	Plumbing supply leak at hall bath was primary source of moisture problems.

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