TRIP REPORT
3 Houses - Houston TX
Problem Home Inspection, Testing and Possible Solutions

DATE
June 26, 2001

PURPOSE

• Assist service and engineering staff in determining the source or probable cause of moisture-related problems and aid in repairs.
• Discuss solutions related to the manufacturing process and propose amendments that would avoid future problems.

INTRODUCTION

• Moisture problems included soft wallboard, discoloring of wallboard and temperature imbalances within the home
• Previously damaged wallboard had been replaced once already by service personnel.  Repairs included placing a vapor barrier between the drywall and the insulation.
• Factory field personnel were on hand to observe and discuss the cause of the problem.

OBSERVATIONS

• Thermostat was set at 78F
• Master Suite gets very cold compared to rest of house.  Homeowner uses bedroom 2 and 3 as office space with various office and computer equipment.
• Window air conditioning unit installed in the end bedroom to assist in cooling.
• Approximate 2 square inch hole noted in supply duct near master bedroom riser.
• The refrigerant line penetration through the air handler cabinet not sealed.
• 3-inch spacer left in plenum.
• Rodent damage in belly (previously noted by homeowner)
• West end wall of master bathroom with possible moisture problem.

TESTING

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.

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.  Interior door closure effect was also measured when the air handler fan operated. 

Pressure Diagnostics w/ AHU (Note: the winds were calm)
Condition	Pressure differential (main wrt outside)
All fans off	0 pa
AHU on	-1.6 pa
AHU on & master suite door closed	-10.7 pa
AHU on & all interior doors closed	-13.0 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).

EFFECTS

• Return air path to AHU is hindered when bedroom doors are closed – especially the master suite door.
• Flow imbalances cause the master bedroom to be overcooled before the other bedrooms are cooled.  This overcooling causes the exterior vinyl covered walls to drop to the ambient air dewpoint temperature or below.
• Duct leakage, on the supply side, causes the entire building to operate at a negative pressure.  Any pathway from the exterior to the interior – such as electrical penetrations- provides a pathway for ambient air to reach interior surfaces.  One such area is at the light fixture mounted on the wall of the master bath.

RECOMMENDATIONS

• Keep thermostat set at 78 F or above.
• The flow imbalances (especially the excessive air in the master suite) should be corrected.
• All duct leaks should be repaired with mastic.  The supply plenum and all risers should be checked and repaired as needed.  The refrigerant line penetration through the air handler cabinet should also be sealed.  The duct leakage should not exceed 3% of floor area or CFM25 less than 40.
• The 3-inch reducer in the supply plenum should be removed.
• A separate return direct to the AHU is needed (through the wall or jump duct) from the master suite.
• Sufficient return air pathways should be installed in the rest of the bedrooms.
• All belly penetrations should be sealed with a permanent, long-lasting seal. No duct tape.
• In general, vinyl covered exterior drywall should not be used in hot and humid climates.

HOUSE 2

DESCRIPTION

• 1368 Sq Ft
• Continuous crawlspace with vented skirting
• Attic flex duct system.
• 3.5-ton A/C compressor – 3 row indoor coil

OBSERVATIONS

• Thermostat was set at 76F
• Homeowner reports that house has a very quick cool down.
• Pink spotting” noted in center and end bedrooms.  Appears to be in path of supply air register throw.  Moisture content measured with a moisture meter appear normal.
• Possible water damaged in hallway due to roof flashing leak at exhaust fan.
• Airflows were measured from each supply register – very close to design flows.

TESTING

Blower door test

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

The values of C and n can be used as inputs for the house airflow equation, Q=C* Pⁿ .  Thus, for any given pressure difference,  P, the airflow crossing the building’s envelope can be determined.

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 CFM_out would be 0.

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.  Interior door closure effect was also measured when the air handler fan operated. 

Pressure Diagnostics w/ AHU (Note: the winds were slight)
Condition	Pressure differential (main wrt outside)
All fans off	0 pa
AHU on	0 pa
AHU on & master suite door closed	0 pa
AHU on & all interior doors closed	0 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).

Airflow testing

The duct tester may also be used as a powered flow hood.  The flow from each supply register was measured and compared to the as designed airflows 

EFFECTS

• It appears that the duct system leakage, return air pathways and airflows to various zones is within acceptable limits.
• The air conditioning system appears to be oversized which allows for the rapid cool down of the home that homeowner commented on.  This leads to short cycling of the compressor and inadequate runtime of the system to provide dehumidification.  The higher interior humidity level causes the occupant to lower the thermostat seeking cooling comfort.
• The supply registers in the bedrooms with the “pink” spotting are blowing cooled air out the exterior vinyl covered gypsum.  This “washing” of the wall by the cool supply air will tend to lower its temperature – more than likely below the exterior dewpoint.
• The wall construction may allow for the intrusion of liquid water.  Though the design appears to be an approved technique, there is a lack of a continuous drainage system.  This may allow water to enter the wall cavity in a liquid form and be trapped.

RECOMMENDATIONS

• Keep thermostat set at 78 F or above.
• The supply registers in the bedrooms should be redirected as to prevent “washing” of the exterior walls.
• The exterior wall design should be invested.  The manufacturer of the siding product should be called in to assist in the investigation and offer their expertise.
• Proper sizing of the air conditioning system is important when it is to used in a hot humid climate.  Or a stand alone dehumidification system should be employed.
• In general, vinyl covered exterior drywall should not be used in hot and humid climates.

DESCRIPTION

• 1368 Sq Ft
• Continuous crawlspace with vented skirting Attic flex duct system.
• 3.5-ton A/C compressor – 3 row indoor coil

OBSERVATIONS

• Thermostat was set at 76F
• Homeowner reports that house has a very quick cool down.
• “Pink spotting” noted in center and end bedrooms.  Appears to be in path of supply air register throw.  Moisture content measured with a moisture meter appear normal.
• Possible water damaged in hallway due to roof flashing leak at exhaust fan.
• Airflows were measured from each supply register – very close to design flows.

TESTING

Blower door test

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

The values of C and n can be used as inputs for the house airflow equation, Q=C* Pⁿ .  Thus, for any given pressure difference,  P, the airflow crossing the building’s envelope can be determined.

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.

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.  Interior door closure effect was also measured when the air handler fan operated. 

Pressure Diagnostics w/ AHU (Note: the winds were slight)
Condition	Pressure differential (main wrt outside)
All fans off	0 pa
AHU on	0 pa
AHU on & master suite door closed	0 pa
AHU on & all interior doors closed	0 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).

Airflow testing

The duct tester may also be used as a powered flow hood.  The flow from each supply register was measured and compared to the as designed airflows 

EFFECTS

• It appears that the duct system leakage, return air pathways and airflows to various zones is within acceptable limits.
• The air conditioning system appears to be oversized which allows for the rapid cool down of the home that homeowner commented on.  This leads to short cycling of the compressor and inadequate runtime of the system to provide dehumidification.  The higher interior humidity level causes the occupant to lower the thermostat seeking cooling comfort.
• The supply registers in the bedrooms with the “pink” spotting are blowing cooled air out the exterior vinyl covered gypsum.  This “washing” of the wall by the cool supply air will tend to lower its temperature – more than likely below the exterior dewpoint.
• The wall construction may allow for the intrusion of liquid water.  Though the design appears to be an approved technique, there is a lack of a continuous drainage system.  This may allow water to enter the wall cavity in a liquid form and be trapped.

RECOMMENDATIONS

• Keep thermostat set at 78EF or above.
• The supply registers in the bedrooms should be redirected as to prevent “washing” of the exterior walls.
• The exterior wall design should be invested.  The manufacturer of the siding product should be called in to assist in the investigation and offer their expertise.
• Proper sizing of the air conditioning system is important when it is to used in a hot humid climate.  Or a stand alone dehumidification system should be employed.
• In general, vinyl covered exterior drywall should not be used in hot and humid climates.

Pictures - House 1