I arrived at the client's home to diagnose a problem with their heating and cooling system. The unit was only installed six months ago and had been experiencing multiple issues since then. I checked the air filter and found that it was causing a 1.0 water column static pressure increase. Air filters should not have that much of an impact on static pressure. I also found a 4 ton heat pump and an 85,000 BTU furnace. The system will need to be set on a box to increase the airflow through the system. I brought the correct sized filter after the installation and explained everything to the customer, including that she will need to purchase different sized filters in the future.