HVAC Systems - Infiltration

What is Infiltration? Infiltration refers to the air leakage or introduction of outside air into a home.

In Cool Calc there are two methods to determine infiltration. You can either use the subjective method or perform a blower door test.

Method 1 - Subjective Method: To use the subjective method simply select "No" when asked if a Blower door test was performed. Then choose how leaky or tight the home is from the "Leakage Category" drop down. If you do not know, Cool Calc will automatically choose a value for you based on the age of the home or code year selected.

Method 2 - Blower Door Method: A more accurate way to determine infiltration in the home is to perform a blower door test. A blower door test requires special equipment that is placed over the front entrance of a home. The home is pressurized and the pressure difference between in inside and outside of the home is then measured.

If you select "Yes" when asked if a Blower door test was performed, you will be prompted to enter an "ELA" value and "Shielding Class".

ELA stands for Effective Leakage area. Some blower doors produce an output reading in CFM50 (airflow difference at a pressure of 50 pascals) or ACH50 (air changes per hour at a pressure of 50 pascals). In either case, these numbers must be converted to ELA for Manual J purposes. A quick conversion method is to divide CFM50 by 10 to get EqLA. Dividing CFM50 by 18 should give you ELA.