- Temperature of the air in the duct
- Air velocity in the duct
- Ambient temperature
- Air duct insulation
Air velocity will also influence the amount of heat gain in the ductwork. High air velocities are recommended when the ducts are carrying cool air because their effect is to reduce the amount of heat gain pickup in the ducts; however they need to be maintained consistent with the acoustic requirements of the installation.
Air Duct Leaks
Air leakage through ducts seams and holes will result in the loss of a portion of the air flowing through the duct and a proportionate reduction in the heating or cooling effectiveness of the system. Depending on the seriousness of the problem, the ductwork can lose up to 1/3 of the air supply in this manner. It is usually a matter of poor workmanship and can be corrected by sealing the seam cracks and holes by calking or soldering. You can also contact an energy contractor in your area to help you seal your air ducts.