Whenever new ductwork is installed, it’s important to not only seal that ductwork, but also to test it. A duct pressure test, also known as a leakage test, checks that the ducts have been sealed effectively, which is important for both efficiency and comfort.
Ductwork has a lot of joints and seams, and a significant amount of air can leak out of those spots if they’re not sealed correctly. In fact, it’s estimated that in the average home whose ducts haven’t been sealed and tested, up to 30% of the heated or cooled air coming from the HVAC system leaks out of the ducts before getting to the registers.
And since the ductwork in most homes runs through unconditioned spaces like the attic or crawlspace, that heated or cooled air simply escapes from the house. Ever had your mother scold you for leaving an outside door open and “air conditioning the whole neighborhood”? Well, if your ducts leak, that’s exactly what you’re doing!
Obviously this situation isn’t good for either efficiency or comfort. The money you spent to condition that air is being wasted, and your home won’t stay evenly warm or cool. The rooms of your home furthest from the HVAC unit will often be most affected, since the air has more chances to escape as it travels a longer distance.
So when you’ve had new ductwork installed, a pressure or leakage test is very important. In order to perform this test, your HVAC technician will first seal off all the vents and registers into your home. Then the technician will use a fan to blow air into the ducts.
Once the pressure inside the ducts reaches a certain level, the technician will then measure how much airflow from the fan is needed to keep the pressure at that level. If the ducts are well-sealed, then the pressure will be easier to maintain. On the other hand, the more air is leaking from the ducts, the more air the fan will have to push into them to maintain the pressure.
If the pressure test finds that there’s significant leakage from the ducts, then the technician will perform further tests to identify exactly where the leaks are occurring so that those spots can be better sealed.
Ultimately, a pressure test will help to make sure that your new ducts are doing what they’re supposed to do—delivering conditioned air right to where you want it, as efficiently as possible.