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ACH 121 Lecture 11a (Thermal & Moisture Protection)
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ACH 121 Lecture 11a (Thermal & Moisture Protection)

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  • WHAT IS THE PURPOSE??? PREVENT ICE BUILD UP IN WINTER AND COOL ROOF IN SUMMER ALSO REQUIRED BY CODES HOW DO YOU ACCOMPLISH IT??? Eave Ventilation SCREENED VENTILATION STRIP OR PERFORATED SOFFIT Gable Vents VENTS AT THE GABLED ENDS OF THE ROOF STRUCTURE (UNDER THE RAKES) Ridge Vents CONTINUOUS METAL OR PLASTIC VENTS
  • WHAT IS THE PURPOSE??? PREVENT ICE BUILD UP IN WINTER AND COOL ROOF IN SUMMER ALSO REQUIRED BY CODES HOW DO YOU ACCOMPLISH IT??? Eave Ventilation SCREENED VENTILATION STRIP OR PERFORATED SOFFIT Gable Vents VENTS AT THE GABLED ENDS OF THE ROOF STRUCTURE (UNDER THE RAKES) Ridge Vents CONTINUOUS METAL OR PLASTIC VENTS

ACH 121 Lecture 11a (Thermal & Moisture Protection) ACH 121 Lecture 11a (Thermal & Moisture Protection) Presentation Transcript

  • Thermal & Moisture Protection Why MOISTURE protection is needed? Types of Moisture Protection Why THERMAL protection is needed? Types of Thermal Protection
  • Moisture Protection What is condensation and why is it an issue in building construction? Types of Moisture Protection Vapor Barriers and Exterior Cladding Materials Roofing Ventilation and Materials Flashing & Gutters/Downspouts This Lecture:
  • Why does a building need to be water tight?
    • Water in the gas form is water vapor which is not damaging to construction until….
    • TEMPERATURE CHANGE!!
    View slide
  • What happens to water vapor when temperature changes?
    • Condenses into a liquid
      • Causes organic materials to decay
      • Metal products to corrode
      • Paint coatings to blister
    • Solidifies when freezes
      • Causes concrete and masonry to crack or spall
    View slide
  • Water Vapor Properties water (liquid state) ice (solid state) vapor (gas state) freezing melting condensation evaporation sublimation
  • Water Vapor Properties
    • Change of state from water or ice to vapor
      • Requires latent heat (heat of transformation)
      • Measured in British thermal units (BTU’s)
    • When water evaporates from a surface, the surface is cooled
      • Example: perspiring skin is the body’s cooling system
  • Water Vapor Properties
    • When water turns to vapor
      • It mixes with air and occupies all available space
    • Amount of water vapor present in air
      • Measurement is relative humidity (RH)
      • Percentage is ratio of actual amount of water vapor in air compared to maximum amount of air at a temperature and pressure
        • Example: 50% humidity contains half the amount of vapor it can hold at that specific air temperature and barometric pressure.
  • Water Vapor Properties
    • At 100% relative humidity, air contains the maximum amount of vapor it can hold; the air is known as SATURATED
    • What happens when temperature of saturated air is lowered…..
    CONDESATION
  • Why is Condensation such an issue?
    • When water vapor is present in a construction or structural assembly or cavity
      • It can condense based on temperature change from the warm side or cool side of the assembly
      • When it condenses, it liquefies causing damage
    Water is the DEATH of a building…… after fire, of course!!
  • Why is Condensation such an issue?
    • Condensation occurs when vapor-laden air at a high enough humidity contacts cool surfaces
      • Cooler climates in occupied, heated buildings
      • Humid, warm climates in air-conditioned bldgs
    • Types of Condensation:
      • Surface condensation
        • Visible, formed on surfaces
      • Concealed condensation
        • Invisible, formed within materials or assemblies
  • Surface Condensation
    • Occurs when surface is cooler than the dew point of the surrounding air
      • Dew point: temperature above freezing at which air becomes saturated and condensation occurs
    • Surface loses heat fast enough to reach dew point
    • Temperature of interior surfaces is dependant on:
      • Air temperatures on both inside and outside
      • Heat transmittance of construction assembly
  • Surface Condensation
    • INSULATION is needed:
      • To reduce heat loss and increase surface temperature
      • Reduces the condensation hazard
      • Keeps surfaces that are in contact with moisture at a temp below dew point
  • Concealed Condensation
    • In cold temperatures, production of vapor inside an occupied building normally raises the vapor pressure
      • Difference from interior pressure to exterior pressure causes vapor diffusion into exterior walls and ceilings
      • Vapor has no where to escape
        • As temperature changes, condensation begins
  • Concealed Condensation
    • VAPOR RETARDER is needed:
      • To prevent moisture migration into concealed spaces
      • Placed near the interior finish
      • Also acts a moisture control measure in exterior wall construction
  • General Purpose of Moisture Protection
    • To prevent water or water vapor from penetrating the building’s skin and/or roof to cause moisture damage
    • Includes decay of organic materials (wood) and mold/mildew of inorganic materials (insulation and plastics)
  • Types of Moisture Protection Roof Ventilation Vapor Retarders & Barriers (building paper) Exterior Finishes & Cladding Roofing Materials Flashing Roof Drainage
  • Roof Ventilation
    • WHAT IS THE PURPOSE???
      • Cool Roof
        • Extend the Life of the Roof Material
        • Reduce Cooling Costs
      • Prevent Ice Build Up
      • Required by codes
  • Roof Ventilation
      • Eave Ventilation
        • screened ventilation strip or perforated soffit
      • Ridge Ventilation
        • Gable Vents
          • vents at the gabled ends of the roof structure (under the rakes)
        • Ridge Vents
          • continuous metal or plastic vents
    • HOW DO YOU ACCOMPLISH IT???
    Eave Venting Ridge Vent Gable Vent
  • PVC (vinyl) Soffit - Perforated Typical Gable Vent
  • Ridge Vent
  • Roof Sheathing “held back” to allow the ridge to be vented
  • Vapor Retarders & Barriers
    • Impedes the passage of water vapor into building assembly before it can condense into liquid
    • Prevents water vapor from penetrating concealed spaces of exterior construction
    • Used on roofs, walls and concrete slabs
  • Vapor Retarders & Barriers
    • WALLS
      • Treated building wrap (Tyvek) Dupont Website
      • Foil-backed sheathing
      • Polyethylene Film
      • Kraft Paper-supported aluminum foil
        • 3-20 ft rolls
    • This house is completely wrapped over the sheathing with a material that has been made to resist water that may get by the siding, but which will let water vapor from inside the house pass out. It also helps to stop drafts through the sheathing joints (air barrier)
  • Vapor Retarders & Barriers
    • ROOFS
      • Felt paper
        • Paper, matted together by pressure and impregnated with asphalt to make waterproof
        • Placed over sheathing
        • 15-30 lb weight (thickness)
      • Bituminous-asphalt paper
    BITUMEN: Natural substances such as asphalt or maltha, which consist mainly of hydrocarbons. BITUMINOUS: Consisting of or resembling bitumen. Can be man made, such as those made from petroleum by-products.
  • Asphalt Felt
  • Exterior Finishes and Cladding
    • Protects interior spaces and construction assemblies from wind, water, sun, snow and other environmental hazards
    • Provides a distinguishing aesthetic feature to the structure
  • Exterior Finishes and Cladding
    • Siding (horizontal or vertical)
      • Vinyl (most popular)
      • Aluminum (hardly used)
      • Wood
        • cedar, Douglas fir, pine, cypress, redwood, spruce, yellow poplar, western hemlock
      • Fibercement
        • Consists of Portland cement, pulp fiber, sand, clay and water
    www.certainteed.com
  • Vinyl sliding installation
  • Vinyl Sliding Profiles double 4” clapboard double 4½” dutchlap double 5” dutchlap double 5” clapboard triple 3” clapboard
    • Vinyl Siding
  • Wood Siding
  • Wood Siding
  • Exterior Finishes and Cladding
    • Masonry veneer
      • Brick
      • Stone
      • Concrete block
  • Brick masonry veneer with vinyl siding
  • Brick Veneer
  • Stone Veneer
  • Stone Veneer
  • Exterior Finishes and Cladding
    • Shakes/Shingles
      • Wood (cedar,cypress)
      • Vinyl
      • Fibercement
        • Certainteed’s Cedar Impressions
    • Red cedar wood shingle siding is applied to this house. The shingles are supplied in random widths and require a substantial amount of labor to fit a water tight, attractive corner. All vertical joints are staggered and the horizontal overlap covers the nailheads. Cedar shingles are often left unfinished to mellow with age
  • Vinyl Shingles
  • Wood Shingle Shakes w/ Stone
  • Exterior Finishes and Cladding
    • Stucco
      • Portland cement, water, sand and a bit of lime
      • Variety of colors and textures
      • Strong, durable
      • Fire-resistant
      • Economical
      • Applied over a galvanized metal lath or mesh
      • Shrinkage is prone to cracking
  •  
  • Exterior Finishes and Cladding
    • Exterior Insulation and Finish System (EIFS)
      • Synthetic stucco
      • Combines insulation with a weather barrier
      • Rigid foam insulation panels glued directly to sheathing
      • Two-layer coat of acrylic compound applied
      • More water resistant and flexible than stucco
  • Exterior Insulation & Finish System (Photo - Insulation Board being attached to Gypsum Board Sheathing)
  • Exterior Insulation & Finish System (Photo – Reinforcing Mesh applied at openings)
  • Exterior Insulation & Finish System (Photo – Cementitious base coat being applied)
  • Exterior Insulation & Finish System (Photo – Reinforcing mesh visible in cementitious base coat)
  • EIFS Finish Coat Applied
  • NEXT CLASS Thermal and Moisture Protection Roofing Materials  Flashing  Gutters and Downspouts Read Chapter 7 and review class lecture notes
  • LAST CLASS Thermal and Moisture Protection Condensation  Vapor Retarders  Roof Ventilation  Cladding Students should have reviewed Chapter 7 and class lecture notes
  • Class Review What is condensation? Why is condensation bad for building assemblies?
  • Class Review What is used to prevent the passage of vapor into the construction assembly? Leading Manufacturer of vapor retarders?
  • Class Review Identify these:
  • Class Review Identify these:
  • THIS CLASS Thermal and Moisture Protection Roofing Materials  Flashing  Gutters and Downspouts
  • Roofing Materials
    • Materials that make the roof watertight
    • 4 General Categories
      • shingles/shakes
      • tiles
      • sheet metal roofing
      • roll roofing
    • Provides a distinguishing aesthetic feature to the structure
  • Roofing Materials-Shingles
    • Small, lightweight units
    • Applied in overlapping layers
    • Staggered vertical joints
    • Overlap between courses is such that the entire surface of roof is covered by a minimum of two layers
    • Asphalt shingles are widely used and cost effective
      • About 90% of single-family homes
      • Lasts for 15-25 years
      • Easy to install
      • Moderate to high fire rating
  • Different Asphalt Shingle Profiles
  • Roofing Materials-Asphalt Shingles Professor Brandi R. Shepard© ACH 121-Materials and Methods 1
  • Professor Brandi R. Shepard© ACH 121-Materials and Methods 1
  • Roofing Materials-Asphalt Shingles Professor Brandi R. Shepard© ACH 121-Materials and Methods 1
    • Die cut from heavy sheets of asphalt impregnated felt
      • Felts contain glass fibers for strength and stability
      • Sheets are faced with mineral granules that wear and add an aesthetic
    • Common size is 12” x 36”
    • Flexible, but not stiff
      • Will bend over valley or ridge
      • Required to be installed over solid sheathing
    Roofing Materials- Asphalt Shingles
  • Roofing Materials- Asphalt Shingles
  • Roofing Materials- Asphalt Shingles
  • Roofing Materials- Asphalt Shingles Professor Brandi R. Shepard© ACH 121-Materials and Methods 1
  • Roofing Felt Asphalt Shingles - Packaged Laid from the Eave up
  • Roofing Materials- Wood Shingles & Shakes
    • Wood Shingles
      • thin, tapered slabs of wood
      • sawn from short pieces of tree truck
      • grain runs length of shingle
    • Wood Shakes
      • Split from wood, not sawn
      • Thicker and irregular
    • Wood species include
      • Red cedar, white cedar
      • Redwood
      • English Oak
      • Southern Yellow Pine
    • Moderately expensive
    • Low to moderate fire rating
  • Roofing Materials- Wood Shingles & Shakes
    • Wood shakes breath better then shingles
      • Due to uneven texture
      • Allows more air circulation between layers
    • Shakes must be applied over 30lb asphalt-felt paper, 18 inches wide
  • Cedar Shake Roof
  • Roofing Materials-Tile
    • Heavy & durable
      • Up to 10 psf (5x weight of asphalt)
      • Requires heavier roof framing
    • High cost
    • High fire rating
    • Materials used
      • Clay
      • Concrete
      • Slate
    • Shapes available
      • Curved & S-shaped
      • Flat, rectangular
    • Styles available
      • Mission  Greek
      • Spanish  Flat
  • Roofing Materials-Tile
    • Clay (terra cotta) Tiles
      • Oldest roofing material
      • used in warmer climates
    • Concrete Tiles
      • Made from high-density concrete
      • Suitable for climates with frequent freeze-thaw cycles
      • Installed over 30-lb underlayment
      • Coated with a resin to make them waterproof
  • Tile Roofing-Terra Cotta
  • Roofing Materials-Tile
    • Slate Tile
      • Long-lasting, very durable
      • Extremely fire-resistant
      • Very high cost
      • Arrives to site ready to install
        • Split, trimmed to size
        • Punched or drilled for nailing
      • Varies in size and thickness
        • 12”-24” l. x 6”-12” w.
        • 3/16” to 2” thick
  • Slate Roofing & Copper Flashing Slate Roof
  • Roofing Materials- Sheet Metal Roofing
    • Metal panels crimped and fastened together
    • Self-oxiding for longevity
    • High cost
    • High fire rating
    • Materials include
      • Enamel-coated galvanized steel
      • Copper & Lead-coated copper
      • Stainless steel
      • Terne & terne-coated stainless steel
  • Roofing Materials- Sheet Metal Roofing
    • Panel roofing
      • Performed
        • Panels are precut to length (eave to ridge)
      • Requires no specialized equipment for installation
        • Fastened to roof with exposed screws sealed with neoprene washers
      • Made from long sheets of galvanized or aluminum steel
      • Panel size is 12” to 24” wide and is length of slope
      • Costs less than others
  • Roofing Materials- Roll Roofing
    • Asphalt Roll Roofing
      • Used primarily on storage sheds & utility buildings
      • Relatively inexpensive
      • Short life span (5-15 years)
      • Comes from the same sheets as asphalt shingles
        • 3 feet wide rolls
  • Flashing
    • Purpose is to prevent the passage of water into a structure from an angle or joint
    • Thin, continuous piece of sheet metal or aluminum
      • Exposed or concealed
    • Used on roofs and walls at areas where materials are joined or penetrated
      • chimneys, roof drains, vent pipes, skylights
      • roof valleys, ridges, hips, changes in roof pitch
      • intersections of roofs and vertical surfaces
      • roof eaves and rakes
  • Flashing
    • Flashing Materials
      • Metals
        • Aluminum, copper, stainless steel, zinc alloy, terne metal, copper-clad lead
        • Mechanically interlocked or welded/soldered
      • Plastics & Modified Bitumens
        • Butyl rubber, EPDM, PVC, neoprene
    • Flashing locations
      • a. rake
      • b. valley
      • c. chimney
      • d. sloped edge of roof at wall
      • e. level edge of roof at wall
      • f. eave
  • “ Hip Cap” (Shingles covering hip rafter) Flashing treatment for hip rafters and valleys
  • Flashing for chimney and vent stacks Copper cricket at back of chimney; also used at bottom of two sloping roofs
  • Flashing
    • Design Factors for Flashing
      • 1. Life span of flashing vs. life span of surrounding materials
      • 2. Corrision
        • Environmental
        • Contact with corroding materials
        • Should not stain or be stained by adjacent materials
        • Should not react chemically with other materials
      • 3. Strength
        • Tensile
        • Compressive
        • Flexural
      • 4. Location
        • Diversion of water
        • Stability to prevent dislocation
  • Roof Drainage
    • Purpose to carry excessive water runoff from sloping roof away from roof system
    • Water is carried from sloping roof to gutters then into downspouts
    • Prevents ground erosion & splashing on walls
  • Roof Drainage
    • Gutter & Downspouts
      • Installed along the eaves
      • Vinyl, aluminum or galvanized steel
      • Seamless gutters are most popular
        • Sheet metal is formed into a profile up to 40 ft
      • Gutters are spiked to eave
        • Slope toward downspout (also called leaders)
        • Water runs down leader & is collected into a storm sewer, drywell system or drainage ditch (code requiring)
        • Splash block is also used
  • Roof Drainage http://raingutterstore.com/rainGutters.asp http://www.tricountyguttering.com/raingutterinstallation.htm
  • Gutter Downspout
    • Materials - Typically
      • Metal - alum., copper
      • Plastic
  • Downspout connected to Underground Piping (splash block also common)
  • Gutters and Downspouts Professor Brandi R. Shepard© ACH 121-Materials and Methods 1
  • NEXT CLASS Thermal Protection Review Chapter 7