Insulation and Interiors Flashcards
Absolute humidity
is the measure of the actual amount of moisture in the air. Measured in grains of moisture per pound of dry air.
Relative humidity
It is the amount of moisture in the air relative to the amount of moisture the air could hold if saturated. Measured in percentage.
Stack effect
Warm air is lighter than cool air because it is less dense. As it rises, it escapes through cracks and holes, the cooler low pressure air brings in cool air from the outside of the house.
Vapour Diffusion
is the movement of vapour without any air movement.
Hygroscopic
Materials with fairly large surface pores, and are able to absorb considerable amounts of water.
HRV
Use one duct to throw warm moist air outside and another duct to draw cool dry air in. On the way through some of the heat from the warm moist exhaust air is transferred to the cool dry air coming through the heat exchanger.
Thermal Conductivity
The number of BTU’s per hour that will move through one square foot of a block of this material that is one inch thick, when the temperature difference from one side of this material to the other is one degree.
Radiation
The transfer of heat through invisible light waves from one body to another.
Convection
the movement of heat through liquids or gases that will flow, such as air or water.
Conduction
the transfer of heat between two bodies by direct contact.
Temperature is measured
in degrees farenheit or celsius
Heat is measured
in BTU’s or British Thermal Units
Sensible heat
Causes the temperature to change.
Latent heat of vaporization
is the name for the significant amount of heat required to change a liquid to a vapour (without changing the temperature)
Wind washing
Wind moving through the roof or wall assembly can reduce the R-value of the insulation dramatically because insulation works by keeping air pockets still
Degree Day
The number of degree days indicate the demand over a heating system. The average temperature for a given day is subtracted from 65°F (18°C)
House wrap vs Building Paper
Building paper generally came in 3’ wide sheets whereas housewrap came in 10’ wide sheets.
Sources of Moisture
people washing their face, hands, and brushing their teeth
taking showers and baths
cooking and washing dishes
washing clothes
washing floors, walls, and furniture
watering plants
people breathing and perspiring
damp soil in subgrade spaces (crawlspaces)
firewood(one cord can release one gallon of water per day as it dries)
pets
How moisture moves
bulk moisture - leaks
capillary action - wicking or rising damp
air transported moisture - the water vapour in the air moves with the air
vapour diffusion - water vapour moves from high to low pressure areas without air movement
Air transported moisture
doors windows chimneys, vents exhaust fans stack effect wind in at the windward side, out at the leeward side
Dew point temperature
The temperature at which condensation will just start to occur. Another way of saying the humidity level is 100%
