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Why do we need thermal and moisture protection?
- Protection from weather
- Temperature extremes create expansion and contraction of materials which can lead to cracking and deterioration.
- Excessive heat loss or gain creates human discomfort and increased equipment and energy costs.
- Leaks cause uncomfortable, costly or hazardous water damage.
- Heat loss and gain is a focus for building codes.
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Moisture problems
- Water: below ground; leak as capillary action or due to hydrostatic pressure.
- Precipitation: fog; drizzle; hail; rain; sleet; snow
- Water Vapor: present in the air as humidity; caused by equipment, activities, human habitation; condensation of the vapor collects on interior surfaces
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CAPILLARY ACTION
The ability of liquid to flow in narrow spaces without the assistance of external forces such as gravity. (porous absorption, ink and paper or a paint brush)
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SURFACE WATER
Consists of surface accumulations of water, caused by rain, thawing ice or snow.
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GROUND WATER
- Water contained in the voids and crevices under the earth's surface.
- Flows very slowly through aquifer (permeable material)
- Control or diversion from buildings.
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GROUND WATER TABLE
- Level below which the earth is saturated with water.
- Determined by test borings.
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Ground Water Control
- In order of watertightness (least to greatest)
- Permeable: capable of being penetrated by water without causing rupture or displacement
- Pervious: permitting leakage or flow of water through cracks, leaks, or openings
- Water-resistant: having no openings larger than capillary pores that permit leakage of water
- Water-repellent: incapable of transmitting water by capillary action, but able to transmit water under pressure
- Waterproof: completely impervious to water, whether under pressure or not.
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DAMPPROOFING
- Materials and methods that prevent moisture from penetrating a building at or below grade.
- Cannot resist constant hydrostatic pressure.
- Treatments
- Preventions
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Dampproof Treatments
- Applied by brushing or spraying a liquid form on foundation or basement walls that make contact with the earth.
- Asphalt base coating: 2 coats
- Cement plaster: densely mixed and troweled or pneumatically applied
- Liquid silicones or plastics
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Dampproofing Prevention
- Draining surface water away from a building by grading
- Provide granular fill under a concrete slab on grade (deter capillary action)
- Install polyethylene film vapor seal over the granular fill
- Footing drains (perforated clay tile) to carry water away from structure
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WATERPROOFING
Consists of materials and methods that prevent water under hydrostatic pressure from penetrating those parts of a building in direct contact with the earth.
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Membrane Waterproofing
- Several layers of asphalt-saturated felt (2 or 3 -ply) hot mopped together with tar or asphalt pitch.
- Most common method for subsurface walls
- Applied to the earth-contacting side of the wall allowing water pressure to force the membrane against the waterproofed surface.
- Protect membrane with a coat of cement plaster, fiberboard, or masonry wythe.
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Waterstop
- A device used to create waterproof construction joints in walls and floors below grade.
- Non-corrosive metal or plastics
- Permit movement without rupture
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PRECIPITATION
- Most common and predictable source of moisture that can damage a structure.
- Control depends on the form and type of roofing
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ROOFING
- Materials and methods used to weatherproof the exterior top surface of a structure.
- Factors affecting selection: climate; fire resistance; type; slope; weight; durability; cost; appearance; personal preference
- Measured by: SQUARE of surface area (100 sq. ft.)
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Roof Selection Factors
- Climate:
- Fire Resistance:
- Type:
- Slope:
- Weight:
- Durability:
- Cost:
- Appearance:
- Personal Preference:
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Climate
- Affects durability of roofing materials.
- Strong winds: damage slate, tile, asphalt shingles
- Hail: punctures roll roofing, break tiles
- Extreme temperatures: expansion / contraction of metal
- High temperature and ultraviolet radiation: affect asphalt
- Salt, air, smoke, industrial gas: corrodes metal (not copper, lead or terne plate)
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Fire Resistance
- Classifications
- A: effective against severe fire test
- B: effective against moderate fire test
- C: effective against light fire test
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Roof Types
- Shed: single slope
- Gable: 2 slopes which meet at a ridge
- Intersecting Gable: 2 gables in opposite direction (Valley downward slope intersection)
- Hip: 4 sides slope and meet at one point
- Mansard: hip with a pitch change high above
- Gambrel: gable with a pitch change high above
- Flat w/ parapets: walls extend beyond top of the roof
- Sawtooth: multiple identical systems of vertical with single slope to one side
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Roof Slope
- (Incline or pitch)
- Expressed as 2:12 (vertical to horizontal units)
- 0-3:12 pitch: bituminous; metal; require continuous waterproof membrane
- 1-4:12 pitch: asphalt shingles; asphalt rolls
- 4-8:12 pitch: all shingles, metals; 5-8 tiles and slate
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Roof Weight
Affects the design, structure and cost.
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Roof Durability
- Function of its quality, climate conditions, and installation.
- Asphalt is least durable
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Roof Cost
- Varies
- Corresponds to durability
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Personal Preference
- Relates to appearance
- Most attractive are more expensive
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ROOF MATERIAL
- Asphalt: built-up; shingles; roll
- Wood: shingles; shakes
- Metal: sheet; corrugated; strip
- Clay, cement, slate: tile
- Glass, plastic: sheets
- Plastic: liquid coatings
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Built-up Roofing
- Consists of layers of asphalt-saturated felts and hot asphalt cement (bituminous materials) (asphalt or coal-tar pitch)
- Designation: 3-ply; 5-ply (# of layers used over the unsaturated base layer sheathing)
- Slag is placed overtop as a flood coat to protect plies from weather
- Asphalt used for sloping roofs
- Coal-tar used for flat roofs
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Asphalt Shingles / Rolls
- Shingles
- manufactured from asphalt-saturated felt and embedded with weather-resistant mineral surface.
- 3ft strips
- Lapped installation and secured with galvanized roofing nails (3:12 pitch min.)
- Rolls
- consists of rolled asphalt-saturated felt
- 3ft wide rolls
- Lapped installation and secured with galvanized roofing nails (1:12 pitch min.)
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Wood Shingles
- Made from red cedar, cypress, and redwood due to decay resistance.
- Standard sizes; tapered thickness;
- Shakes (hand-split)
- Lapped installation over sheathing and fastened with aluminum or galvanized nails (4:12 pitch min. to allow ventilation)
- Designation: 16" 5/2 (total thickness of butt end of 5 shingles = 2")
- Random (3-14" width) packaged by the square
- Dimension (5-6" width) packaged by 1000
- bundle
- Need fire protected
- Expensive
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Metal Roofing
- Include galvanized iron, copper, aluminum, terne plate
- Disadvantages: corrosion, galvanic action, expansion / contraction
- Standing / Batten seam: repetitive pattern
- Corrugated: allows more movement
- Tiles: galvanized or aluminum; installed over felt and sheathing secured with similar metal fasteners
- <3:12 pitch: soldered or welded
- 3:12 < pitch: screws or nailed with compatible metals
- Durable; expensive and attractive oxidizing
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Tile Roofing
- Heavy; durable; permanent; fireproof; expensive
- Applied over sloping roof surfaces
- Lapped over preceding course and nailed
- Clay Tile
- manufactured from the same clays used for bricks
- Patterns: greek; roman; Spanish; mission; shingle; english
- Cement Tile
- tiles manufactured from Portland cement and fine aggregate.
- Less expensive than clay
- Slate Tile
- Tiles quarried from natural rock and split into thin rectangular slabs
- Sizes: 12"x16"; 3/16 to 1/2" thick
- Texture: smooth; rough
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Sheet Roofing
- Glass and translucent plastic
- Flat sheets for small areas; corrugated for large areas
- Poor fire resistance; wire-reinforced or fiberglass
- Thermal expansion
- Low strength
- Use: skylights; clearstories; greenhouses; areas requiring light and weather protection
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Plastic Coating Roofing
- Single-ply sheets; single-ply with foam; liquid
- Use: curved; thin shelled concrete surfaces
- Substrate must be of a type the coating will bond to
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HUMIDITY
- Condensation of water vapor.
- Higher the air temperature = higher humidity
- Moves from high to low pressure areas and from inside to outside a building
- Moisture forms on the cool side of a material
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RELATIVE HUMIDITY
- Amount of water vapor the air contains in relationship to the amount it could contain.
- Expressed as %
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DEW POINT
100% relative humidity when water vapor turns into a liquid
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VAPOR BARRIER
- Materials that prevent the passage of water vapor.
- Types: aluminum foil; sheet plastic; asphalt-saturated felt
- Installed on warm side
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THERMAL CONTROL
- Slow down heat gain or loss to improve human comfort and conserve energy.
- Conduction: when materials or objects are in direct contact.
- Convection: process that occurs in a fluid medium (air or liquid)
- Radiation: take place between two objects not in contact and not shielded from each other
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Thermal Control Methods
- Caulking and weatherstripping: cracks; openings
- Tinted, reflective or insulating: windows
- Thermal insulation: wall; roof
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R-VALUE
- Thermal Resistance
- High degree of reflectivity
- sfhrdegF/BTU
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k-VALUE
- Thermal conductivity (expressed as U)
- k = 1/R
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Insulation Types
- Arranged from least to most insulating
- Loose fill
- Reflective
- Board or sheet
- Batt or Blanket
- Foam
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Loose Fill Insulation
- glass or mineral wool, vermiculite, perlite
- used for wall cavities and flat air spaces such as attics
- Rvalue=3.90 (4" thick)
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Batt or Blanket Insulation
- glass or mineral wool enclosed by paper or aluminum - vapor barriers available
- used for air spaces in framed walls, floors, and ceilings
- Rvalue=11.00 (3 1/2" thick)
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Board or Sheet Insulation
- cork, glass or mineral fibers, paper pulp
- used for wall sheathing and rigid roof insulation
- Rvalue=2.75 (1" thick)
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Reflective Insulation
- aluminum foil often in combination with layers of paper and air spaces
- used for roof, wall and floor insulation plus vapor barrier
- Rvalue=1.39 (1" air space with 2 reflective surfaces)
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Foam Insulation
- plastics, spray type or panels
- used for sheathing, irregular spaces
- Rvalue=6.00 (1" panel)
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FLASHING
Material used to provide a seal and prevent water penetration at joints exposed to the weather, intersections or materials, and expansion or contraction joints.
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