Transcript Source - Midwest Residential Energy Conference
Humidity
Robert Fehr Professor Emeritus Department of Biosystems and Agricultural Engineering University of Kentucky
144 btu/lb
WATER VAPOR PROPERTIES
W A T E R (liquid state) 970 btu/lb sublimation 1223 btu/lb I C E (solid state) V A P O R (gas state)
Definitions
Humidity: The amount of water vapor in the air Relative humidity: The amount of water vapor actually in the air divided by the amount of water vapor the air can hold. Saturation of air: The condition under which the amount of water vapor in the air is the maximum possible at the existing temperature and pressure. 100% Relative Humidity
Definitions
Wet bulb temperature: The lowest temperature that can be obtained by evaporating water into the air at constant pressure.
Dew point: the temperature air would have to be cooled to in order for saturation to occur.
Psychometrics Basic Concepts
Saturation Line PSYCHROMETRIC CHART Lexington, Kentucky USA
BAROMETRIC PRESSURE 28.874 inches of Mercury Staturation Line 0 5 10 15 20 25 Linric Company Psychrometric Chart, www.linric.com
30 35 40 45 50 55 60 65 DRY BULB TEMPERATURE - °F 70 75 80 85 90 95 100 105 110 115 120 40 30 20 10 80 70 60 50 140 130 120 110 100 90 210 200 190 180 170 160 150
Constant Dry Bulb Temperature PSYCHROMETRIC CHART Lexington, Kentucky USA
BAROMETRIC PRESSURE 28.874 inches of Mercury Constant Dry Bulb Temperature 0 5 10 15 20 25 Linric Company Psychrometric Chart, www.linric.com
30 35 40 45 50 55 60 65 DRY BULB TEMPERATURE - °F 70 75 80 85 90 95 100 105 110 115 120 40 30 20 10 80 70 60 50 210 200 190 180 170 120 110 100 90 160 150 140 130
Constant Relative Humidity PSYCHROMETRIC CHART Lexington, Kentucky USA
BAROMETRIC PRESSURE 28.874 inches of Mercury Constant Relative Humidity 0 5 10 15 20 25 Linric Company Psychrometric Chart, www.linric.com
30 35 40 45 50 55 60 90% 80% 70% 60% 50% 40% 30% 20% 10% RE LATIVE HUMID ITY 65 DRY BULB TEMPERATURE - °F 70 75 80 85 90 95 100 105 110 115 120 60 50 40 30 20 10 90 80 70 120 110 100 170 160 150 140 130 210 200 190 180
Constant Humidity Ratio PSYCHROMETRIC CHART Lexington, Kentucky USA
BAROMETRIC PRESSURE 28.874 inches of Mercury Constant Humidity Ratio 0 5 10 15 20 25 Linric Company Psychrometric Chart, www.linric.com
30 35 40 45 50 55 60 65 DRY BULB TEMPERATURE - °F 70 75 80 85 90 95 100 105 110 115 120 60 50 40 30 100 90 80 70 20 10 210 200 190 140 130 120 110 180 170 160 150
Constant Humidity Ratio PSYCHROMETRIC CHART Lexington, Kentucky USA
BAROMETRIC PRESSURE 28.874 inches of Mercury
Saturation Line
0 5 10 15 20 25 Linric Company Psychrometric Chart, www.linric.com
30 35 40 45 50 55 60 65 DRY BULB TEMPERATURE - °F 70 75 80 85 90 95 100 105 110 115 120 70 60 50 40 30 20 10 210 130 120 110 100 90 80 200 190 180 170 160 150 140
Constant Wet Bulb Temperature
Dew Point Dew Point
Humidity Ratio
Psychometrics of Heating
Psychometrics of Cooling
PSYCHROMETRIC CHART Lexington, Kentucky USA
BAROMETRIC PRESSURE 28.874 inches of Mercury 85
Annual Hourly Outside Air Conditions – Lexington KY
80 85 WE T B UL B T EM PE RA TURE - °F 80 75 1 5 .0
75 70 65 40 35 30 25 20 15 10 20 0 5 5 10 15 2 .5
0 5 10 15 20 25 Linric Company Psychrometric Chart, www.linric.com
25 30 30 1 3 .0
35 35 40 45 40 50 45 55 1 3 .5
50 60 65 90% 80% 60 55 70% 60% 50% 40% 1 4 .0
30% 20% 10% RE LATIVE HUMIDIT Y 45 50 55 60 DRY BULB TEMPERATURE - °F 65 70 75 70 80 1 4 .5
S P E CI F IC V O L UM E ft ³/lb O F DRY A IR 85 90 95 100 105 110 60 50 40 30 20 10 120 110 100 90 80 70 210 200 190 180 170 160 150 140 130
PSYCHROMETRIC CHART Lexington, Kentucky USA
BAROMETRIC PRESSURE 28.874 inches of Mercury 85
Annual Hourly Outside Air Conditions – Lexington KY
80 85 WE T B UL B T EM PE RA TURE - °F 80 75 1 5 .0
75 70 65 40 35 30 25 20 15 10 20 0 5 5 10 15 2 .5
0 5 10 15 20 25 Linric Company Psychrometric Chart, www.linric.com
25 30 30 1 3 .0
35 35 40 45 40 50 45 55 1 3 .5
50 60 65 90% 80% 60 55 70% 60% 50% 40% 1 4 .0
30% 20% 10% RE LATIVE HUMIDIT Y 45 50 55 60 DRY BULB TEMPERATURE - °F 65 70 75 70 80 1 4 .5
S P E CI F IC V O L UM E ft ³/lb O F DRY A IR 85 90 95 100 105 110 60 50 40 30 20 10 120 110 100 90 80 70 210 200 190 180 170 160 150 140 130
PSYCHROMETRIC CHART Lexington, Kentucky USA
BAROMETRIC PRESSURE 28.874 inches of Mercury 85
Annual Hourly Outside Air Conditions – Lexington KY
80 85 WE T B UL B T EM PE RA TURE - °F 80 75 1 5 .0
75 70 65 40 35 30 25 20 15 10 20 0 5 5 10 15 2 .5
0 5 10 15 20 25 Linric Company Psychrometric Chart, www.linric.com
25 30 30 1 3 .0
35 35 40 45 40 50 45 55 1 3 .5
50 60 65 90% 80% 60 55 70% 60% 50% 40% 1 4 .0
30% 20% 10% RE LATIVE HUMIDIT Y 45 50 55 60 DRY BULB TEMPERATURE - °F 65 70 75 70 80 1 4 .5
S P E CI F IC V O L UM E ft ³/lb O F DRY A IR 85 90 95 100 105 110 60 50 40 30 20 10 120 110 100 90 80 70 210 200 190 180 170 160 150 140 130
PSYCHROMETRIC CHART Lexington, Kentucky USA
BAROMETRIC PRESSURE 28.874 inches of Mercury 85
Annual Hourly Outside Air Conditions – Lexington KY
80 85 WE T B UL B T EM PE RA TURE - °F 80 75 1 5 .0
75 70 65 40 35 30 25 20 15 10 20 0 5 5 10 15 2 .5
0 5 10 15 20 25 Linric Company Psychrometric Chart, www.linric.com
25 30 30 1 3 .0
35 35 40 45 40 50 45 55 1 3 .5
50 60 65 90% 80% 60 55 70% 60% 50% 40% 1 4 .0
30% 20% 10% RE LATIVE HUMIDIT Y 45 50 55 60 DRY BULB TEMPERATURE - °F 65 70 75 70 80 1 4 .5
S P E CI F IC V O L UM E ft ³/lb O F DRY A IR 85 90 95 100 105 110 60 50 40 30 20 10 120 110 100 90 80 70 210 200 190 180 170 160 150 140 130
PSYCHROMETRIC CHART Lexington, Kentucky USA
BAROMETRIC PRESSURE 28.874 inches of Mercury 85
Annual Hourly Outside Air Conditions – Lexington KY
80 85 WE T B UL B T EM PE RA TURE - °F 80 75 1 5 .0
75 70 65 40 35 30 25 20 15 10 20 0 5 5 10 15 2 .5
0 5 10 15 20 25 Linric Company Psychrometric Chart, www.linric.com
25 30 30 1 3 .0
35 35 40 45 40 50 45 55 1 3 .5
50 60 65 90% 80% 60 55 70% 60% 50% 40% 1 4 .0
30% 20% 10% RE LATIVE HUMIDIT Y 45 50 55 60 DRY BULB TEMPERATURE - °F 65 70 75 70 80 1 4 .5
S P E CI F IC V O L UM E ft ³/lb O F DRY A IR 85 90 95 100 105 110 60 50 40 30 20 10 120 110 100 90 80 70 210 200 190 180 170 160 150 140 130
PSYCHROMETRIC CHART Lexington, Kentucky USA
BAROMETRIC PRESSURE 28.874 inches of Mercury 85
Annual Hourly Outside Air Conditions – Lexington KY
80 85 WE T B UL B T EM PE RA TURE - °F 80 75 1 5 .0
75 70 65 40 35 30 25 20 15 10 20 0 5 5 10 15 2 .5
0 5 10 15 20 25 Linric Company Psychrometric Chart, www.linric.com
25 30 30 1 3 .0
35 35 40 45 40 50 45 55 1 3 .5
50 60 65 90% 80% 60 55 70% 60% 50% 40% 1 4 .0
30% 20% 10% RE LATIVE HUMIDIT Y 45 50 55 60 DRY BULB TEMPERATURE - °F 65 70 75 70 80 1 4 .5
S P E CI F IC V O L UM E ft ³/lb O F DRY A IR 85 90 95 100 105 110 60 50 40 30 20 10 120 110 100 90 80 70 210 200 190 180 170 160 150 140 130
App for Air Properties
Moisture Balance
Outside Air Entering @ Outside Conditions Moisture Added People, Animals, Plants, Foundation Moisture Stored Fabric, Carpet, Wood Moisture Removed Dehumidifier Inside Air Leaving @ Inside Conditions
Winter Moisture Balance
Outside Air Entering @ Outside Conditions 32F 85% = 78 lbw/day 0.80 ACHn Moisture Added People, Animals, Plants, Foundation Moisture Stored Fabric, Carpet, Wood Moisture Removed Dehumidifier 134 lbw/day drying potential Inside Air Leaving @ Inside Conditions 70f 60% = 212 lbw/day
Winter Moisture Balance
Outside Air Entering @ Outside Conditions 53F 85% = 174 lbw/day 0.80 ACHn Moisture Added People, Animals, Plants, Foundation Moisture Stored Fabric, Carpet, Wood Moisture Removed Dehumidifier 38 lbw/day drying potential Inside Air Leaving @ Inside Conditions 70f 60% = 212 lbw/day
Winter Moisture Balance
Outside Air Entering @ Outside Conditions 53F 85% = 85 lbw/day 0.40 ACHn Moisture Added People, Animals, Plants, Foundation Moisture Stored Fabric, Carpet, Wood Moisture Removed Dehumidifier 21 lbw/day drying potential Inside Air Leaving @ Inside Conditions 70F 60% = 106 lbw/day
Summer Moisture Balance
Outside Air Entering @ Outside Conditions 85F 50% = 283 lbw/day 0,80 ACHn Moisture Added People, Animals, Plants, Foundation Moisture Stored Fabric, Carpet, Wood Moisture Removed Dehumidifier 27 lbw/day added Inside Air Leaving @ Inside Conditions 76F 60% = 256 lbw/day
Sources of Moisture
• • • • • People – Respiration – Transpiration Pets Plants Showers and Bathing Dishwashing, and Cooking – 0.1 lb of water per ft3 of NG
Sources of Moisture
• Foundations – Difficult to quantify
Effect of Humidity on Moisture Production
Sources of Moisture - People
Design Residential Moisture Generation Rates (TenWolde and Walker 2001) Number of Number of Moisture Generation Rate Bedrooms Occupants lb/h lb/day gallon/day
1 2 0.7
16.8
2.01
2 3 3 4 4 5 Additional +1 1.1
1.3
1.4
per bedroom 26.4 ` 31.2
33.6
+0.1 2.4
3.17
3.74
4.03
0.29
Sources of Moisture - Plants
• • • Potted flowers: 0.011–0.022 lb/h Potted plants: 0.015–0.033 lb/h Medium-size rubber plant: 0.022–0.044 lb/h
Sources of Moisture - Pets
• It is a function of the weight of the animal.
A medium-size dog weighing 22 lb contributes about 0.015 lb/h, 0.36 lb/day, 0.043 gallons/day
Sources of Moisture – Showers and Baths
• • 5.7 lb/h for showers – 5 minute shower = 0.475 lbs – 15 minute shower = 1.425 lbs 1.5 lb/h for baths – 5 minute bath = 0.125 lbs – 15 minute bath = 0.375 lbs
Suggested Dehumidifier Size
Pints per day of Dehumidifier Capacity Source: Association of Home Appliance Manufacturers
Humidity Level vs Ventilation Rate
The Effect of Indoor Humidity on Water Vapor Release in Homes Anton TenWolde Crystal L. Pilon ASHREA 2007
0.8 ACHn
Older House
0.4 ACHn
0.35 ACHn
New House
0.20 ACHn
Recommended Humidity Levels
Soruce: American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE).
Surface Condensation
• • Occurs when surface is cooler than the dew point of the surrounding air Temperature of interior surfaces is dependent on: – Air temperatures on both inside and outside – Heat transmittance of assembly
Surface Condensation
• Raising the R value of a assembly – Increases the inside surface temperature – Reduces the condensation hazard
Concealed Condensation
• In cold temperatures, production of vapor inside an occupied building normally raised the vapor pressure – Difference for interior pressure to exterior pressure cause vapor diffusion into exterior walls and ceilings – Vapor has no where to escape • As the temperature drops, condensation begins.
When is Condensation an Issue
• • Cooler climates in occupied, heated buildings Humid, warm climates in air-conditioned buildings
Why is Condensation an Issue
Water is the DEATH of a building …after a FIRE
Window Temperature Profile
70 60 50 40 30 20 10 0
14% 44% 66%
Single Pane Double Pane Double Pane, low-E, Argon
70 60 50 40 30 20 10 0
Uninsulated Wall Temperature Profile
30% Brick OSB Wall Cavity Air Space Gypsum Board
70 60 50 40 30 20 10 0
Insulated Wall Temperature Profile
9% Brick OSB Cavity Insulation Air Space Gypsum Board
Vapor Retarders & Barriers
• • • Impedes the passage of water vapor into a building assembly before it can condense into a liquid Prevents water vapor from penetrating into concealed space of exterior construction Used on roofs, wall, and concrete slabs
Moisture Migration Into Walls
Source: Building Science Corporation
Rain Event Creates Vapor Pressures
Exterior Conditions
Temperature 80 °F Relative Humidity 75% Vapor Pressure 2.49 kPa Solar radiation strikes wall
Conditions within Cavity
Temperature 100 °F Relative Humidity 100% Vapor Pressure 6.45 kPa
Interior Conditions
Temperature 75 °F Relative Humidity 60% Vapor Pressure 1.82 kPa Brick veneer is saturated with rainwater 1-inch air space Felt paper Vapor is driven both inward and outward by a high vapor pressure differential between the brick and the interior and the brick and the exterior Fiberboard sheathing Fiberglass insulation Polyethylene Interior gypsum board Source: Building Science Corporation
Measuring Air Moisture Content
• • • • • •
Chilled mirror dew point hygrometers Capacitive humidity sensors Resistive humidity sensors Thermal conductivity humidity sensors Physical change sensors Psychrometers
–
(Wet and Dry Bulb Thermometers)
Human Hair Hygrometer
Swing Psychrometer
Sling Psychrometer Scale
Difference Between Dry Bulb and Wet Bulb Temperatures
T db
- T
wb
(
o
F)
Wet Bulb Depression Table
Relative Humidity - RH (%) Dry Bulb Temperature - T
db
(
o
F) 60 64 68 72 76 80 84 1 2 3 4 5 6 7 8 9 10 94 90 84 78 73 68 63 58 54 49 95 90 85 80 75 70 66 61 57 52 95 90 85 81 76 72 67 63 59 55 95 91 86 82 78 73 69 65 61 57 96 91 87 83 79 75 71 67 63 59 96 92 88 84 80 76 72 68 65 61 96 92 88 84 80 77 73 70 66 63 88 96 92 89 85 81 78 74 71 68 64
Temperature and RH Logger
Using a Room Dehumidifier
Large Room Dehumidifier
Using a Room Dehumidifier
Inside Duct Large Room Dehumidifier
Dehumidification
• Primary – Air Conditioner – Size • Runtime – SHR (Sensible Heat Ratio) • Varies with Web Bulb Temperature (RH) – Two Speed • Typically 1 ton less at low speed
Air Sealing and Runtime
0.80 ACHn 0.40 ACHn
Psychometrics of Cooling
Whole House Dehumidifier
Homeywell TrueDRY™
Dehumidifier Performance
• • • Capacity: 21 pints/day (60 ºF [15.6 ºC], 60 %RH) = 21.9 lbw/day 42 pints/day (70 ºF [21.1 ºC], 60 %RH) = 43.8 lbw/day 65 pints/day (80 ºF [26.7 ºC], 60 %RH) = 67.8 lbw/day • Energy Performance: 4.7 pints per kilowatt hour (KWH) – 4.903 pounds per KWH
Dehumidifier Components
Source: Homeywell TrueDRY™
Whole House Dehumidifier Installation Options
Source: Homeywell TrueDRY™
Desiccant Dehumidifier
Source: Novelaire ComfortPlus™ 300 Combined Desiccant and DX Cooling
Desiccant Dehumidifier
Source: Novelaire ComfortPlus™ 300
Evaporator Condenser
Economizers for Humidity Control
Ventilation for Moisture Control
PSYCHROMETRIC CHART Lexington, Kentucky USA
BAROMETRIC PRESSURE 28.874 inches of Mercury 85
Annual Hourly Outside Air Conditions – Lexington KY
80 85 WE T B UL B T EM PE RA TURE - °F 80 75 1 5 .0
75 70 65 40 35 30 25 20 15 10 20 0 5 5 10 15 2 .5
0 5 10 15 20 25 Linric Company Psychrometric Chart, www.linric.com
25 30 30 1 3 .0
35 35 40 45 40 50 45 55 1 3 .5
50 60 65 90% 80% 60 55 70% 60% 50% 40% 1 4 .0
30% 20% 10% RE LATIVE HUMIDIT Y 45 50 55 60 DRY BULB TEMPERATURE - °F 65 70 75 70 80 1 4 .5
S P E CI F IC V O L UM E ft ³/lb O F DRY A IR 85 90 95 100 105 110 60 50 40 30 20 10 120 110 100 90 80 70 210 200 190 180 170 160 150 140 130