Module 4: The house as a system Flashcards
what are the 3 main elements of the house-as-a-system approach?
heat flow, air flow and moisture flow
how fast heat moves depends on what 2 things?
how large the temperature difference is between locations and how much resistance to heat flow there is between two objects, surfaces or fluids
heat flows in what 3 ways?
radiation, convection and conduction
what is radiation?
is heat transferred by any warm object to its surroundings.
what is thermal agitation?
when the heat in the object causes its molecules to get excited so they move around more quickly.
what is convection?
is heat transferred by the movement of a fluid, such as water or air, in relationship to a heat source.
what is the convective loop?
as the fluids molecules are warmed by the heat source, they become more active and less dense, and so begin to rise -then, as the molecules get farther from the heal source they cool and begin to fall, starting the cycle over as they again near the heat source
what is conduction?
is the direct transfer of heat through solid objects, by means of their molecules bumping together
what are conductors?
materials that allow heat to flow easily
what are insulators?
materials that slow down the flow of heat
explain R-value (or RSI)
it describes how well a material insulates. the higher the R-value per unit of thickness, the slower the rate of heat movement through it.
what are the 3 way that air pressure differences between the interior and exterior of house can impact the house?
wind effect. stack effect and combustion and ventilation
what is the infiltration of air?
when the wind blows on one side of a house, creating a high-pressure zone. This “positive” pressure forces air into the envelope through cracks and holes
what is the exfiltration of air?
on the other sides of the house where the wind isnt blowing, a low-pressure zone is created and this “negative” pressure pulls air out of the house
what is the stack effect?
is the vertical flow of air, caused by differences in pressure and temperature in a house. ex: heating system
