As you may be able to see from the picture, a dog chewed into the bottom of this return air plenum which is located in the garage. The furnace being located in a garage area is very common, the furnace platform or return air platform/plenum in this case is one piece. So the outdoor air that is in the garage area is being pulled into the heating and cooling system. Then the heating and cooling system must heat or cool the outdoor air, not the conditioned air in the home. And this my friends is not good!
Your heating and cooling system is now responsible for heating and cooling conditioned air that it has conditioned in addition to outdoor air. This system will never keep you comfortable! So, check those HVAC units that are located in the garage. You never know what they have been subjected too in the past few weeks or months and may need to be repaired. Check them especially if you are having system performance problems or concerns.
Pets, bicycles, lawn mowers, cars and really any moving object can penetrate the old sheet rock casings for older systems. And penetrations are bad!
Call A.I.R. Plus if you need help with your system. We would love to help you!
Have a blessed day!