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Proper Ventilation Sealing Techniques

Part of our spring and fall maintenance checklists involves looking for leaks and drafts in the home. But once you’ve found them, what do you do? The answer is not “a strip of duct tape as a patch” but it isn’t terribly difficult to fix most of the leaks in your home. Leaks in your ventilation system lead to excess strain on your central air system, but they also lead to sky-high utility bills every month. You pay for the costs of heating and cooling the interior walls of your home when a leak is not addressed. So take the time, find the leaks, and get them repaired!

How to Ventilation Identify Leaks

The simplest way to find a leak is with a visual inspection. In rooms, this involves looking at door and window jambs, or examining any exterior pipes and vents for cracks in the sealant. For the ventilation system itself, you’ll need to go into the attic and take a close look at the ventilation ducts. Look for joint gaps, wall punctures, or seam tears along the ductwork. All of these will leak climate controlled air into spaces where it isn’t needed.

You can also use a smoke (or incense) stick to help you identify drafts. For rooms, turn off your central air and close all doors and windows. Light a smoke stick and watch the smoke trail to see where it goes. It should follow the room’s air currents and flow through any drafts, identifying leaks. You can do the same thing with your ducts by turning on the fan and running a smoke stick along the exterior to see where a draft will blow the smoke away.

You can also hire a professional contractor like Cassel. We use special systems to build backpressure and identify if there’s a leak in your ventilation system. Once we know there’s a leak, we can track it down and give it a professional seal that will last for years.

Duct Tape Doesn’t Last

You’d think that duct tape would be a good way to patch any holes or seams (it sure “seams” that way since it’s in the name doesn’t it?). The problem is that duct tape doesn’t last forever. In extreme cold or heat, the adhesives on duct tape can become brittle. Duct tape actually loses its adhesiveness in about a month, leaving you back where you were, but with a gummy residue left on the surface of the duct.

Mastic is Better

So what should be used instead? Well for windows and doors, repainting and weather proofing is the way to go. Small leaks can be fixed with foam insulation or rubber weather-strips. When you need to fix a seal on your ductwork, mastic adhesive resin is the way to go.

Mastic adhesive retains its sealing resiliency because it doesn’t dry and harden. It has a consistency similar to peanut butter, so it can be difficult to work with if you aren’t used to it. A proper seal involves cleaning the edges (or the hole your patching), applying mastic, and then covering the seam with mesh tape. Larger cracks and seams (1/16th to 1/8thof an inch) require more work, and we recommend seeking professional help for these kinds of repairs.


Cassel Home Comfort Heating & Cooling is committed to being your best HVA/C contractor choice in Central Illinois in both Value and Customer Service! Call us to maintain your heating, ventilation, and air conditioning systems in the Champaign, IL area: (217) 866-1596.

A live call center and friendly technicians are standing by 24 hours a day, 7 days a week to help you with all your heating and cooling questions.

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