Construction - Air Volume
Construction - Air Volume
When it comes to heating, cooling, and keeping the air healthy in a building it is very important to be able to calculate air volume. To accurately calculate heating and cooling requires knowing the volume of air but there are also many other factors so we will not do calculations on these areas.
This lesson will be focused on air replacement calculations. If air is not circulated it becomes stagnant which is unhealthy. The air also stratifies because of temperature differences so the warm air goes to the ceiling while the cool air settles to the floor. For maximum comfort, we generally want the warm air on the floor and the cool air at the ceiling.
The amount of airflow is measured in Air Changes per Hour (ACH) which is an indication of how many times in an hour the equivalent amount of the air that is in the room has been circulated. This does NOT mean that every molecule of air in the room has been circulated every hour. It means that enough air is moving so that all of the air could be replaced that many times. Every room will have dead zones where the air does not circulate as freely as other zones.
Recommended ACH range from 3-15 for most buildings. Rooms such as storage in the basement will be on the low end of the range while kitchens or public use rooms will be on the upper end.
Step 1: Calculate the volume of air in each room. (cubic feet)
Step 2: Multiply by the recommended ACH for each room. (cubic feet per hour)
Step 3: Divide by 60. (cubic feet per minute, CFM)
Step 4: Divide each room volume by the total volume and multiply by 100. (percent of total airflow required)
This information can be used to determine the size of the furnace or A/C that will be needed in the building as well as the size of the ducting going to each room.
Directions for This Lesson:
Watch the video below to learn more and then try to answer the Practice Questions.
Required Video:
Practice:
Extend your learning with these practice questions and then complete the worksheet.
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