1 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012 eere.energy.gov

Moisture AssessmentWEATHERIZATION ENERGY AUDITOR SINGLE FAMILY

WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012

2 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012 eere.energy.gov

By attending this session, participants will be able to:• Analyze the symptoms of moisture problems in houses.

• Identify moisture sources.

• Explain moisture terms and concepts.

• Demonstrate how to measure relative humidity.

• Demonstrate how to use a psychrometric chart.

• Apply moisture control strategies.

• Use moisture assessment tools.

Learning ObjectivesMOISTURE ASSESSMENT

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Symptoms #1

Excessive window condensation

Photo courtesy of PA WTC

MOISTURE ASSESSMENT

4 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012 eere.energy.gov

Symptoms #2

Frost on underside of roof sheathing

MOISTURE ASSESSMENT

Photo courtesy of PA WTC

5 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012 eere.energy.gov

Symptoms #3

Mold on interior surfaces

Photo source: PA WTC Photo

MOISTURE ASSESSMENT

Photo courtesy of PA WTC

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Symptoms #4

Peeling Exterior Paint

MOISTURE ASSESSMENT

Photo courtesy of PA WTC

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Standing Water in Basements

MOISTURE ASSESSMENT

Photo courtesy of PA WTC

Symptom #5

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• Foundations

• Unvented space heaters

• Unvented dryers

• Disconnected ventilation fans

• Drying wood indoors

• Excessive mechanical or passive humidification

Moisture Sources

These water stains are a result of fan venting into the attic.

MOISTURE ASSESSMENT

Photo courtesy of PA WTC

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Sources of Water VaporMOISTURE ASSESSMENT

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• Condensation: water vapor transformed to liquid water

• Evaporation: liquid water transformed to water vapor

• Absolute humidity (vapor pressure): the ratio of water vapor to a given volume of air

• Relative humidity (RH): the ratio of the amount of moisture in the air compared to amount of moisture that the air can hold

• Dew point: the temperature at which condensation occurs

Important Terms and ConceptsMOISTURE ASSESSMENT

11 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012 eere.energy.gov

Measuring Relative Humidity

Sling Psychrometers• Two thermometers side by side• One is wrapped in wet wick (wet

bulb), the other is dry (dry bulb)• Spinning it around speeds

temperature stabilization• Plot wet bulb and dry bulb

temperature on psychrometric chart to determine dew point and RH

Photos courtesy of Bacharach

MOISTURE ASSESSMENT

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Dry bulb = 80°Wet bulb = 66°Dew point = 60°RH = 50%

Grains of w

ater per pound of dry air

MOISTURE ASSESSMENT

Psychrometric Chart #1

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156

Psychrometric Chart #2

78

Grains of w

ater per pound of dry air

MOISTURE ASSESSMENT

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Grains of w

ater per pound of dry air

MOISTURE ASSESSMENT

Psychrometric Chart #3

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Grains of w

ater per pound of dry air

MOISTURE ASSESSMENT

Psychrometric Chart #4

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Grains of w

ater per pound of dry air

MOISTURE ASSESSMENT

Psychrometric Chart #5

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• Warm, wet air contacting cold surfaces creates condensation instantly.

• Cold winter air typically contains very little moisture and therefore has a low RH. When that air is heated, the RH drops even lower.

• RH below 15% can lead to respiratory problems, failure of furniture glue and other problems.

RH: Things to RememberMOISTURE ASSESSMENT

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Attic Case Study

Floored Attic and First Condensing Surface

MOISTURE ASSESSMENT

Photo courtesy of PA WTC

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Possible Causes• Moderate to high interior moisture source

• Attic surface temps are below the dew point of the indoor air

• Air leaks to attic

Control Strategies• Source control

• Air seal the attic

Attic Case – Causes & SolutionsMOISTURE ASSESSMENT

20 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012 eere.energy.gov

Basement Case Study

Mold on cool interior corner

Symptom

• Condensation evident on basement walls

Reason

• Light to moderate interior moisture source

• Basement walls are below the dew point of the indoor air

MOISTURE ASSESSMENT

Photo courtesy of PA WTC

21 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012 eere.energy.gov

Control moisture sources.

Remove susceptible materials.

Educate occupants to:

• Mechanically dehumidify.

• Increase air flow in basement (fans).

• Close basement openings during hot humid periods.

Basement Case Study Solutions MOISTURE ASSESSMENT

22 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012 eere.energy.gov

Symptoms• Wet wood• Condensation on

foundation surfacesPossible Reasons• High ground moisture

source• Warm humid air entering

vents from outside• Crawl space surfaces

are below the dew point of the outside air

Crawl Space Case Study

Water droplets of condensation on AC ducts.

MOISTURE ASSESSMENT

Photo courtesy of PA WTC

23 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012 eere.energy.gov

• Install a ground vapor retarder.

• Control moisture sources and remove susceptible materials.

• Consider converting to a conditioned crawl space.

Crawl Space Case Study Solutions

Conditioned crawlspace with air sealed and insulated walls.

MOISTURE ASSESSMENT

Photo courtesy of INCAP

24 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012 eere.energy.gov

Clear understanding of moisture management principles.• Senses - Visual inspection

o Evidence of condensationo Evidence of mold

• Communication Skillso Know what questions to asko Documentation is vital

• Wood Moisture Metero To make quantitative assessments on wood moisture content

• Psychrometero To determine real time RH levels

• Digital Camera

Tools of the TradeMOISTURE ASSESSMENT

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PhotoSource: PA WTC

MOISTURE ASSESSMENT

Moisture Meters

Photos courtesy of PA WTC

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• The first step in doing a moisture assessment is to look for visible signs of moisture and moisture sources in the house.

• Plotting the wet bulb and dry bulb temperatures on a psychrometric chart gives dew point and relative humidity.

• Understanding the effects of temperature and vapor pressure on RH can help identify solutions.

• Source control, air sealing, ventilation, and thermal improvements are important moisture mitigation strategies.

• Photos and diagnostic equipment help document existing conditions.

SummaryMOISTURE ASSESSMENT