Water/Vapor Barrier

Moisture enters through a building by...

- Bulk moisture: water enters through holes/cracks/gap (have rainscreen & cavity) - Capillary action: moves liquid through porous material (must use sealant) - Air leakage: carries water vapor through holes & cracks - Vapor diffusion: moisture moves from high to low

Vapor barrier vs vapor retarder

- Class I or II of vapor retarder is considered a vapor barrier *Use barrier in cold climates * Use retarder in all other climates

Types of waterproofing materials

- Sheet membrane (built-up layers that may be loosely applied) - Fluid-applied systems (Cont./seamless membrane) - Cementitious systems (portland cement, sand & waterproof agent) - Bentonite systems (expands in presence of moisture)

Blindside waterproofing

- When an adjacent building buts up against a new building - Put in place against existing building before concrete wall is formed

vapor retarder

- material of low permeance installed in construction to prevent moisture from entering a point where it can condense into a liquid. METAL FOIL, PLASTIC, TREATED PAPER, FLUID-APPLIED MEMBRANES Warm side

Methods of dampproofing

-admixture in concrete -bituminous coatings -cementitious coatings -membranes -plastics

Perm rating for aluminum foil

0

Class I Vapor Retarder & examples

0.1 or less perm (backside of interior gyp board in cold climates) - Polyethylene rubber sheet - Glass - Sheet metal

Class II vapor retarder rating & examples

0.1-1.0 perm rating (backside of interior gyp board) - Asphalt coated paper (30lb) - Polystyrene - Plywood

Class III vapor retarder rating & examples

10 or more (only on interior side of frame wall) - Gyp board - Fiberglass insulation - Cellulose insulation - Concrete block - Brick - House wrap - Board lumber

Vapor-impermeable barriers

Acts as both an air barrier and a vapor barrier *Air leakage carries water vapor through holes & cracks

Vapor retarder classes

Class 1: Impermeable (0.1-1.0 perm) least moisture to pass through) Class 2: Semi-impermeable (0.1-1.0 perm) Class 3: Permeable (1.0-10 perm) most moisture to pass

Polyethylene sheet is what level of class vapor retarder

Class I (0.1 perm or less) MOST EFFECTIVE VAPOR RETARDER

Residential building codes require what level of class vapor barrier

Class I or II

Damp proofing

Typically refers to coatings used on slabs and foundations below grade - NOT BELOW WATER TABLE (hydrostatic)

Perm ratings and terminology

Vapor impermeable: Less than 0.1 Semi-impermeable: 0.1 - 1.0 Semi-permeable: 1.0 - 10 Permeable: 10 or over ANYTHING LESS THAN 1 = VAPOR BARRIER

______ air holds more water than _____ air

WARM air holds more water than COLD air

Permeance and moisture protection

Want lower permeance = better for moisture protection

In cold climate what side of wall is vapor barrier placed?

Warm side of insulation

What side to place vapor barrier

Warm side of insulation

5 materials commonly used for moisture protection (in buildings)

Methods of damp proofing - Admixture: add to concrete to repel water (may reduce strength) - Bituminous coatings: asphalt/coal-tar (material applied to exterior side of foundation wall) - Cementitious coatings: Portland cement mortar troweled over foundation wall - Membranes: built-up layers of hot/cold applied asphalt felts - Plastics: used above grade dampproofing

capillary action

Moves liquid through porous material (surface tension)

Water proofing positions

Positive: most common, placed on side with moisture Negative: Place on side NOT with moisture Blindside: Applied before element in place

Permeance

Property of a material that prevents water from diffusing through it. A lower permeance is better for moisture protection

Sheet-applied membrane

Seamed system that could lead to weaker protection Not good for water moisture area

Dew point

temperature at which air is saturated and condensation forms

Purpose of air barrier

Control air leakage in the building enclosure - NOT MOISTURE

water proofing

Control of moisture and water that is subject to hydrostatic pressure BELOW WATER TABLE

Damp proof vs water proof

Damp: control moisture NO hydrostatic pressure Water: Hydrostatic pressure

Temperature at which water vapor is not condensing into water any faster than water would be vaporizing into air....known as

Dew point

Bulk Moisture

Flow of water through holes, cracks, and other discontinuities into walls

liquid-applied membrane

Fluid system Good for odd shapes