Presentation is loading. Please wait.

Presentation is loading. Please wait.

3/11/2004 Objectives Analyze potential for mold and condensation in different climates and different building types Describe moisture transport in buildings.

Published byCaroline Woods Modified over 9 years ago

Similar presentations

Presentation on theme: "3/11/2004 Objectives Analyze potential for mold and condensation in different climates and different building types Describe moisture transport in buildings."— Presentation transcript:

1 3/11/2004 Objectives Analyze potential for mold and condensation in different climates and different building types Describe moisture transport in buildings Mechanisms Driving forces ARE 381E

2 Cooling climate Summer – AC cools surfaces
3/11/2004 Cooling climate Summer – AC cools surfaces RH near surfaces increases Outdoor air is “poison” from a moisture control perspective Does not let surfaces dry out ARE 381E

3 How do you limit potential for condensation?
3/11/2004 How do you limit potential for condensation? Duct and diffuser design As low as possible ventilation rates Treat (dehumidify) incoming air Maintain building at positive pressure Vapor diffusion retarder ARE 381E

4 Heating or Mixed Climate
3/11/2004 Heating or Mixed Climate What influences RH near surfaces of exterior walls? Insulation level Thermal bridging Temperature difference (inside temperature) Indoor moisture levels More likely to get mold at summer or winter design conditions in Austin? ARE 381E

5 Mold in Austin ASHRAE design weather conditions:
3/11/2004 Mold in Austin ASHRAE design weather conditions: Winter -1.3 °C DB Inside 21 °C, 50 % RH Summer 35.8 °C DB, 23.4 °C WB Inside 26 °C, 50 % RH Winter inside air dew point: 10.2 °C Winter DB corresponding to 70% RH: 16 °C Summer outside air dew point: 18.1 °C Summer DB corresponding to 70% RH: 20.3 °C What temperature is air blowing out of a register? ARE 381E

6 3/11/2004 ARE 381E

7 Other Causes of Mold Plumbing leak, condensation, envelope leak
3/11/2004 Other Causes of Mold Plumbing leak, condensation, envelope leak Building materials get wet Don’t dry out because of Insufficient air flow Air that is too humid Oversized air conditioners Mold growth hard to arrest ARE 381E

8 Exterior Closet Example
3/11/2004 Exterior Closet Example Heating climate (dry outside air) Closet in exterior corner of bedroom Mold growth What can you do to control mold? In what order would you implement suggestions? ARE 381E

9 Stopping Condensation
3/11/2004 Stopping Condensation Raise surface temperature Reduce heat flow to exterior Increase heat flow to surface Reduce interior moisture (vapor pressure) Source control Dilution Dehumidification ARE 381E

10 Causes of moisture problems
3/11/2004 Causes of moisture problems Exterior corners Low air circulation Wind-washing Higher heat loss (wood instead of insulation) Greater surface area to volume ratio Exterior wall/roof/floor intersections Higher heat loss ARE 381E

11 More causes of moisture problems
3/11/2004 More causes of moisture problems Impermeable wall covering in cooling climates Thermal bridges Insulated walls in heating/mixed climates ARE 381E

12 3/11/2004 Condensing Surfaces ARE 381E

13 Moisture Movement Thus far we have studied moisture problems
3/11/2004 Moisture Movement Thus far we have studied moisture problems How does moisture move through buildings? MCH does this anecdotally and qualitatively We will explore this quantitatively Everything can be explained with the 2nd Law of Thermodynamics ARE 381E

14 3/11/2004 Moisture Transport Quantitatively and qualitatively describe transport by Liquid flow Capillary suction Air movement Vapor diffusion ARE 381E

15 Liquid Flow Requirements Driving forces? Liquid water Driving force
3/11/2004 Liquid Flow Requirements Liquid water Driving force Hole Driving forces? ARE 381E

16 How do you stop liquid flow?
3/11/2004 How do you stop liquid flow? Minimize moisture source or minimize driving force Site selection Drainage Overhangs/architectural detailing Irrigation Minimize holes Waterproofing ARE 381E

17 Site Selection Grading Building should be at high point
3/11/2004 Site Selection Grading Building should be at high point Ground should slope downwards away from building Sounds simple, not always possible Water flows downhill, account for it ARE 381E

18 Drainage Gutters and downspouts Impermeable caps
3/11/2004 Drainage Gutters and downspouts Direct away from building Impermeable caps Free-draining backfill material Also building materials Drain away moisture that enters building Flashing ARE 381E

19 Driving Force Minimization
3/11/2004 Driving Force Minimization Leaky siding, air gap, tight sheathing Drainage/flashing at bottom of air gap No straight-through holes Kerfs to address surface tension Minimizing wind exposure WDR (momentum) Pressure difference ARE 381E

20 3/11/2004 ARE 381E

21 Waterproofing Idea is to eliminate holes Membranes/barriers
3/11/2004 Waterproofing Idea is to eliminate holes Membranes/barriers Downside? Control joints Organized concrete failure Treat failed cracks Disadvantages? ARE 381E

22 Capillary Suction Paper towel example
3/11/2004 Capillary Suction Paper towel example What makes a good capillary medium? Small pores (but not sealed) Small contact angle (hydrophilic) What is the driving force? Surface tension Units on surface tension? Is surface tension a function of temperature? Is it only a liquid phenomena? Ref: Carey (1992) Liquid-Vapor Phase-Change Phenomena ARE 381E

23 Capillary Action (quantitative)
3/11/2004 Capillary Action (quantitative) Liquid water Water moves from big capillary pores to small capillary pores Water vapor (at equilibrium) s = ρRTln Temperature does influence vapor motion through capillary pores What direction is vapor flow? Capillary vapor transport is from high T to low T ARE 381E

24 How do we stop capillary action?
3/11/2004 How do we stop capillary action? Get rid of the moisture source Make the pores bigger Capillary break Seal the pores Give the water someplace else to go ARE 381E

25 Stopping Capillary Suction Below Grade
3/11/2004 Stopping Capillary Suction Below Grade Bituminous liquid (tar-like material) to seal pores on exterior of foundation Does not span big cracks Gravel around foundation (with below grade drain) Install capillary breaks Air gaps, insulation gaps ARE 381E

26 Stopping Capillary Suction Above Grade
3/11/2004 Stopping Capillary Suction Above Grade Paint Caulk small air gaps Disadvantages? Make large air gaps (vented) between siding and wall and between shingles and roof decking Use building paper or bricks or other material to absorb moisture ARE 381E

27 Air Movement Simplest form of vapor transport Driving force?
3/11/2004 Air Movement Simplest form of vapor transport Driving force? Air moves from high pressure to low pressure Pressure increases with temperature (IGL) Flow is from high temperature to low temperature ARE 381E

28 Source Control Exhaust ventilation Dilution Dehumidification
3/11/2004 Source Control Exhaust ventilation Bathrooms, kitchens, dryers, unvented combustion, wood storage, construction materials Condensate drainage Vapor-diffusion barrier Dilution Dehumidification ARE 381E

29 How to Stop Air Movement
3/11/2004 How to Stop Air Movement Air retarders Air sealing Caulk and foam Dense-pack cellulose insulation DO NOT FORGET ABOUT VENTILATION ARE 381E

30 3/11/2004 Vapor Diffusion Movement of water vapor from high concentration to low concentration Mechanism is random molecular motion Some materials are impermeable to vapor diffusion Other materials retard vapor transmission ARE 381E

31 Governing Equation For Diffusion
3/11/2004 Governing Equation For Diffusion w water vapor flux [M/t/A, kg/s/m2] µ permeability [perms∙in, perm = grain/(hr∙ft2∙in Hg)] Permeance [ng/(s·m2·Pa)] p is water vapor pressure x is distance along flow path Water diffuses from high vapor pressure to low vapor pressure Permeability is a function of temperature in materials Very ugly non-linear relationship ARE 381E

32 Permeability and Resistance
3/11/2004 Permeability and Resistance ASHRAE ch. 25 Table 9 What has greater average permeability? Brick Concrete Aluminum foil Air Polyethylene Latex enamel paint Latex primer/sealer paint ARE 381E

33 More questions Does permeability or permeance matter?
3/11/2004 More questions Does permeability or permeance matter? How do you measure permeability/permeance? Wet-cup/dry-cup tests What is a vapor-barrier/ vapor-retarder? How do tears, voids, gaps affect vapor-retarder performance? Is this the same as for air barriers? ARE 381E

34 Protecting against Vapor Diffusion
3/11/2004 Protecting against Vapor Diffusion Above grade Use a vapor retarder Interior in heating climates Caveat about cladding moisture Exterior in cooling climates But, what happens in the “other” season? And, what happens when moisture does get into the building assemblies? “Smart” retarders Impermeable to vapor, but “permeable” to liquid Low permeability at low RH, high permeability at high RH ARE 381E

35 Protecting against Vapor Diffusion
3/11/2004 Protecting against Vapor Diffusion Below grade Damp proofing Vapor diffusion retarders on different surfaces Insulation on exterior of foundation ARE 381E

36 Objectives Quantitatively and qualitatively describe transport by
3/11/2004 Objectives Quantitatively and qualitatively describe transport by Liquid flow Capillary suction Air movement Vapor diffusion References: MCH ch. 2, ASHRAE ch. 23 & ch. 24 ARE 381E

Download ppt "3/11/2004 Objectives Analyze potential for mold and condensation in different climates and different building types Describe moisture transport in buildings."

Similar presentations

Mold Hazards And Prevention. © Business & Legal Reports, Inc. 0809 Session Objectives Understand the potential health hazards of exposure to mold Detect.

Mold Hazards And Prevention. © Business & Legal Reports, Inc Session Objectives Understand the potential health hazards of exposure to mold Detect.
ENERGY STAR Home Sealing Improve home comfort and reduce energy bills.

ENERGY STAR Home Sealing Improve home comfort and reduce energy bills.
ENERGY STAR Qualified Homes

ENERGY STAR Qualified Homes
The Building Skin: SPAIGR

The Building Skin: SPAIGR
Moisture Control. Indications of Excessive Moisture Condensation,frost or ice on the inside surface of windows Damp spots on ceilings or inner surfaces.

Moisture Control. Indications of Excessive Moisture Condensation,frost or ice on the inside surface of windows Damp spots on ceilings or inner surfaces.
GY205 Weather and Climate Lecture 3.

GY205 Weather and Climate Lecture 3.
1 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – July 2012eere.energy.gov Building Science Basics WEATHERIZATION INSTALLER/TECHNICAN FUNDAMENTALS.

1 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – July 2012eere.energy.gov Building Science Basics WEATHERIZATION INSTALLER/TECHNICAN FUNDAMENTALS.
Building Envelope. Energy Conservation House design and orientation Lifestyle changes Energy efficiency.

Building Envelope. Energy Conservation House design and orientation Lifestyle changes Energy efficiency.
“Sustainable Building Systems and Construction For Designers” Chapter 7: Walls.

“Sustainable Building Systems and Construction For Designers” Chapter 7: Walls.
Building Enclosure Moisture Management Institute (BEMMI)

Building Enclosure Moisture Management Institute (BEMMI)
Walls Ron Gatepain constructionsite.

Walls Ron Gatepain constructionsite.
Heating and Air Conditioning I

Heating and Air Conditioning I
The House as a System 1. Systems in a Home Electrical Plumbing Comfort Control (HVAC) Structural Moisture Control Air Infiltration Thermal Insulation.

The House as a System 1. Systems in a Home Electrical Plumbing Comfort Control (HVAC) Structural Moisture Control Air Infiltration Thermal Insulation.
WALTER SCARBOROUGH CSI CCS CCCA SCIP AIA 214.491.7385 D+D Specifiers Series Sponsored by Air Barriers.

WALTER SCARBOROUGH CSI CCS CCCA SCIP AIA D+D Specifiers Series Sponsored by Air Barriers.
1 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – August 2010eere.energy.gov Energy Movement WEATHERIZATION ENERGY AUDITOR SINGLE FAMILY.

1 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – August 2010eere.energy.gov Energy Movement WEATHERIZATION ENERGY AUDITOR SINGLE FAMILY.
Lesson 3 How does radon enter a home?. Slide 3-1 Predicted average indoor radon levels (U.S.) This map cannot be used to determine the radon level of.

Lesson 3 How does radon enter a home?. Slide 3-1 Predicted average indoor radon levels (U.S.) This map cannot be used to determine the radon level of.
Station 4 ?? Temperatures and Moisture Moisture Meters Pin Contact Data Loggers Spot Temperature Meter Thermal Imager Cautions and Safety.

Station 4 ?? Temperatures and Moisture Moisture Meters Pin Contact Data Loggers Spot Temperature Meter Thermal Imager Cautions and Safety.
1 Steps to Healthier Homes n Start with People n House as a System n Keep It: Dry Clean Pest-Free Ventilated SafeContaminant-Free Maintained n Making it.

1 Steps to Healthier Homes n Start with People n House as a System n Keep It: Dry Clean Pest-Free Ventilated SafeContaminant-Free Maintained n Making it.
Assumptions about Indoor Environments Mark Lawton P.Eng Patrick Roppel M.A.Sc.

Assumptions about Indoor Environments Mark Lawton P.Eng Patrick Roppel M.A.Sc.
1 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – July 2012eere.energy.gov Moisture Barriers WEATHERIZATION INSTALLER/TECHNICIAN FUNDAMENTALS.

1 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – July 2012eere.energy.gov Moisture Barriers WEATHERIZATION INSTALLER/TECHNICIAN FUNDAMENTALS.

Similar presentations

Ads by Google