Air ducts lose or gain heat whenever your hvac equipment is running. If the temperature inside your duct is different from the air outside, then a heat loss or gain will occur. This loss or gain is something that needs to be considered when designing ductwork in a home or office. This aspect of heat transmission will depend on some or all of the following factors:
- Temperature of the air in the duct
- Air velocity in the duct
- Ambient temperature
- Air duct insulation
If the ducts are used to convey heat, excessive heat loss from the air ducts will reduce the efficiency of the heating system. This will result in a total loss of heating effect if the heat loss occurs in the ductwork passing through an unheated area but it can be considerably reduced with proper insulation. This heat loss can also occur in heated spaces but run the risk of poor air distribution. These same conditions exist when the ducts carry cool air. When air passes through spaces subject to the cooling effect of air conditioning insulating the ducts will effectively reduce the amount of heat gain.
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 LeaksAir 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.
