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48 Cards in this Set
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- Back
- 3rd side (hint)
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what is temperature |
the measurement of the average kinetic energy of the particles of a substance. all materials possess a certain internal energy |
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outdoor air temperature |
fluctuates over time with seasonal and daily temperature changes (sun is main heat source) |
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heating season/cooling season |
exterior temperatures in Canada tend to be below the human comfort zone and heat energy must be added to the interior environment to raise the temperature |
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indoor climate |
a regulate balance of air temperature and humidity • ASHRAE (American soviety of heating, refrigeration and air conditioning engineers) has sponsored many studies of indoor comfort |
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what is the human comfort zone dependant on? |
age, health, activity, individual preference |
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comfort zone |
temperature: 20-22 °C (winter) RH: 35-55% |
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causes of interior air movement |
• air leakage in buildings • exterior air pressure effects |
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air leakage in buildings |
• air pressure increases as air is heated and expands • air under pressure travels through any openings in building envelope • as warm air rises and escapes the building, cold outdoor air may be sucked into the building through the crawl space or first floor • loss of warm air increases energy costs from rehearing • warm moist air may be carried into the wall and roof cavities causing condensation when hitting colder materials |
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exterior air pressure effects |
• exterior air pressure differentials can cause auction that will pull in more cold air as the warm air is pushed out |
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techniques to reduce air leakage |
1. weather stripping around door openings 2. caulking/sealants around openings 3. panel and sheet products in large sizes 4. expanding foam around openings 5. use air barriers |
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what is an air barrier? |
a material applied in the building envelope to block the passage of bulk air through the building envelope |
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an air barrier must be: |
1. impermeable to the passage of air 2. continuous with sealed joints 3. strong enough to resist wind forces 4. durable |
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air barrier locations |
• located on the interior or exterior of the building • blocks the effects of external air pressure differences |
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what are the 3 types of air barrier systems? |
1. polyethylene film (6 mil) 2. air right drywall system 3. exterior air barriers |
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polyethylene film air/vapour barrier system |
• sheer polyethylene film can be used to create both an air barrier and vapour barrier • must meet building code requirements for vapour permeance (use 6 mil thickness) • may be inadequate in resisting wind pressure stress over time (plastic gets brittle) • must be taped/sealed at joints, top and bottom of sheets in order to act as an air barrier and a vapour barrier |
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air tight drywall system (ADA) |
• AIR: gypsum board is used to create an air tight barrier. sealants and air tight gaskets are used to create air barrier at openings, top and bottom of sheets • VAPOUR: vapour retarding paint may be used as a vapour barrier. polyethylene film is therefore not required as a vapour barrier |
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what regulated interior temperature? |
• forced air furnaces • electric baseboard heaters • radiant floors • fireplace - gas, electric, or solid fuel • warm bodies • lighting • equipment and appliances |
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areas o heat loss or gain in buildings |
• roof/walls • openings in envelope (Windows, doors, skylights, pipes, vents) • foundation/crawl space • interfaces (connections) between any of these areas |
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temperature differentials |
heat moves from an area or material of high temperature to low temperature until thermal equilibrium is reached |
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what are the three ways heat can be transferred? |
1. conduction 2. convection 3. radiation |
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conduction |
heat is directly transferred - materials must be touched and and heat transfer takes place through the materials from one molecule to another
building example: • in winter single glazed Windows feel very cold to touch • the heat from your fingers is being conducted directly to window = heat loss |
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convection |
heat is carried by movement of air fluid - warm air rises and cool are sinks, creating a convective cycle
building example • cold surface of window cools the surrounding air • as temperature of air drops, it becomes denser and falls to the floor • a baseboard heater under window will warm the air (which then rises and replaces colder air) |
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radiation |
electromagnetic waves carrying heat energy can radiate from a warmer source to a colder surface (without direct contact of air movement)
building example: • gas fireplace adds radiant energy to a room and warms surfaces in direct line of fire • a water filled radiation increases surface temperatures with radiant heat |
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bulk air leakage |
• a form of convection • bulk air can escape through cracks and openings in the building envelope due to a difference in air pressure • heat loss will occur as warmed interior air exits the building and is replaced by colder exterior air being pulled in at lower parts of the building • adding an effective air barrier is the best way to reduce this type of heat loss |
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wind |
• Result of air pressure differentials • directional (NESW) • oceans + mountains and high + low daily pressure changes affect wind direction
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exterior air barrier: house wrap |
• located over exterior sheathing in place of traditional building paper • house wrap acts as an: - air barrier - moisture barrier (most inward barrier to water located on exterior) - NOT a vapour barrier because water will pass through
ex. tyvek |
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temperature gradient through wall |
• from inside to outside materials in the wall assembly will change temperature depending on the material and use of insulation • to resist the loss of heat through the wall, add low-conductance insulation which changes the temperature gradient across the wall - temperature is more sharply divided between indoor and outdoor extremes (the sheathing temperature is lower) |
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thermal conductance/resistance |
• all materials conduct heat • how much heat conducted is dependent on the resistance of the molecular structure of the material to the transfer of heat energy • metals conduct easily • plastics don't conduct easily |
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measuring thermal conductance/resistance |
• measured in terms of the resistance of the material to the passage of heat • thermal resistance (RSI metric or R-value imperial) |
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insulation |
• reduces heat gain/loss • reduce thermal movement by isolation and separation of warm sources from cold and vice versa |
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insulation material qualities |
• use low-conductance material (plastics, mineral materials, not metals) • reduce contact points (material touches at intervals) • add dead-air space (small isolated air spaces not affected by other convective currents) |
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forms of insulation |
1. fibre batts 2. rigid insulation panels 3. spray on insulation 4. loose fill insulation |
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fibre batts |
• typically fibreglass in wood frame construction and mineral wool (for fire protection) batt insulation • typically 15-1/4" x 48" • fits in between studs in exterior frame walls or joist/rafter spaces • must fill the cavity without any air spaces • friction fit not crammed in fit - stuffing batt insulation into walls densifies the insulation, increases contact points and reduces effectiveness as an insulating material |
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rigid insulation panels |
• installed over sheathing/foundation walls insulating panels • rigid plastic insulation • extruded polystyrene, polyurethane, polyisoxyanurate • varying panel sizes from 24" wide to 4' x 8' sheets |
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spray on insulation |
• expanding foam plastic products (ex. polyurethane) • generally used in specialty areas over pipes, underground garage ceilings, and around window/door openings |
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loose fill insulation |
• cellulose products (recycled paper products, plant-based material) • generally used in frame wall and attic spaces • issues: - combustibility - settling |
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exterior air barriers: self-adhering membrane |
• membrane is adhered over exterior sheathing in place of traditional building paper • membrane acts as an: - air barrier - vapour barrier (insulation must be placed to the exterior) - moisture barrier (most inward barrier to water located on exterior)
ex. Peel and stick, blue skin |
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thermal bridging |
different rates of heat transfer between metal studs and insulated stud spaces can create surface staining on building exteriors |
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older buildings |
don't have much rot and decay because: • subject to a lot of air leakage • warm air leaves the building and is replaced by cooler air • drying can occur in the building to reduce moisture content and decay problems • are drafty and have higher energy costs |
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newer buildings |
measures were taken to reduce energy consumption • adding building insulation • double-glazed and thermally broken windows • vapour barriers (to reduce damage caused through vapour diffusion) • air barriers |
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ventilation |
• an air barrier prevents the loss of heated moist air from the building • energy costs are saved • material durability inside the wall and ceiling is preserved • air quality can be degraded by a build-up of contaminants Ventilation is important in an air tight house |
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a sealed system |
• fresh air by ventilation is required for human comfort and health • household activities can raise interior RH levels • interior RH levels need to be reduced through ventilation to prevent condensation and resulting possible mould problems and prevent odour build-up |
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off-gassing |
• new building materials can contribute to contamination (give off fumes from their constituent ingredients) • these contaminants need to be vented out of the building |
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heat gain |
• when air temperature is higher than the interior • Windows can increase the amount of heat gain as heat is radiated through the glazing I tot the interior
visible and infrared light |
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heat gain and windows |
• south and west windows are prime areas of solar heat gain • use low-e glazing to reduce this effect or use less glazing |
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heat gain/loss with materials |
• all materials on the outside of the building will gain or lose heat due to the presence or absence of solar energy • the surface of these materials may be much higher than the surrounding air temperature depending on its colour/texture • this heat can be conducted inwards through the building envelope which can lead to drying of materials via evaporation and high humidity/reverse vapour drive |
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thermal storage |
• all objects radiate thermal energy • some materials store a lot of thermal energy and radiate energy slowly in the infrared wavelength • different materials absorb and radiate thermal energy at different rates
ex. bricks that are warmed by the sun will hold the heat for hours and gradually disperse the heat back into the atmosphere - some materials conduct heat very quickly and have a low heat capacity for thermal storage ex. a metal window frame will quickly radiate internal heat outwards into the exterior air like a radiator |
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ways to stop heat loss |
• add an air barrier (fill all cracks, services penetration) • use thermally non-conductive materials where possible (add insulation) |
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