Ducts that transport cool air also need a good thermal insulation solution. The insulation maintains the lower temperature inside the duct by insulating it from the warmer ambient air temperature. If the cool air in the duct is heated by the surrounding air, the HVAC system functions less effectively and you will need more energy to maintain the duct's correct temperature. If the ducts are properly insulated, the whole ventilation system will work as designed and you need less equipment calibration.
Huge problems occur when condensation builds up on the outside of ducts containing material with a lower temperature than the ambient air temperature. With high humidity, the air can easily condense on the outer surface of ducts. When this happens, water starts to drip and causes damage, such as discoloration to ceilings and floors. Over time, water can cause damage to the ducts and reduce their service life. Condensation also occurs inside the duct if the situation is reversed.
Prevent condensation easily by using the correct insulation solution. Apply insulation of the correct thickness to keep the insulation surface temperature higher than the ambient air temperature. Also use an effective water vapour barrier to prevent moisture permeating the insulation.
In the table below you can see when condensation insulation is required.
||Air in the duct
||Location of the duct
|Outdoor air duct,
||In heated, warm space (higher temp than in the duct)
||Condensation on outer surface
||Thermal insulation +
vapour barrier, taping
|Heated incoming air,
||In unheated, cold space
||Condensation on inner surface
|In heated, warm space
||Thermal insulation to reduce energy loss
Calculate the correct thickness of the insulation easily by using Paroc’s calculation program PAROC Calculus. If you are required to insulate for thermal purposes and for fire protection, always place the fire insulation closest to the duct and the thermal insulation and vapour barrier on top of the fire insulation. For more information regarding fire protection of ducts, please contact your local Paroc representative.