Infiltration of cold air into a warm house during winter
through the cracks around doors, windows, and other openings
is a major source of energy loss since the cold air that enters
needs to be heated to the room temperature. The infiltration is
often expressed in terms of ACH (air changes per hour). An
ACH of 2 indicates that the entire air in the house is replaced
twice every hour by the cold air outside.
Consider an electrically heated house that has a floor space
of 150 m2 and an average height of 3 m at 1000 m elevation,
where the standard atmospheric pressure is 89.6 kPa. The
house is maintained at a temperature of 22°C, and the infiltration
losses are estimated to amount to 0.7 ACH. Assuming
the pressure and the temperature in the house remain constant,
determine the amount of energy loss from the house
due to infiltration for a day during which the average outdoor
temperature is 5°C. Also, determine the cost of this energy loss for that day if the unit cost of electricity in that area is
$0.082/kWh.