Protecting the Heat Duct Crossover Gasket

During last couple of training courses held earlier this year, we talked quite a bit about problems with the heat duct crossover gasket. We all agree that the “through the rim joist” heat duct crossover is preferable to the old flex duct, but keeping the gasket intact during installation is a common problem.

Heat duct crossover gasket before installation.

It has been my experience that the top reason for consumer complaints is generally the result of excessive heat loss which impacts the home owners comfort and leads to unreasonably high heating/cooling bills. If we can keep the gasket intact throughout the installation process, it can go a long way in fixing this problem.

An example of a gasket damaged during the installation process.


The HUD code requires that all heat ducts be “substantially air tight” so it is important that care is taken to assure that this gasket survives installation. To do that, But, how can we protect this gasket during installation?

Easy to see how these gaskets get torn apart.


For the past couple of years, I have been encouraging installers to fabricate and protect each “through the rim joist” heat duct crossover gasket with a temporary metal shield. Now, it doesn’t have to be anything fancy, just a simple “L-shaped” piece of aluminum coil stock at least 16” long. Bend the metal to make an “L” about 8” high with a 90° bend of about 2”.

A simple aluminum shield to protect the heat duct crossover gasket.

Place one of these shields over each crossover gasket and hold it in place with a screw through the bottom. Once the home is in its final position, remove the screws and pull out the shields.

Several installers have started doing this and they all agree that it works great. However, these installers have offered some feedback to improve on this idea:

  1. Remove the shield BEFORE lagging the floors together. Otherwise it can be difficult to remove.
  2. Hang tags or something similar from each shield to make them easier to spot and less likely to be forgotten.

Now, lets take this one step further, why not start telling the manufacturers to install heat duct crossover shields in the factory? Just think how much they would save in service! Hey, there is no harm in asking!

So, if you haven’t already tried this, give it a go! Maybe you have a better method to protect this gasket, if so, feel free to share it in the comments section!

Finally, be safe and wash your hands!

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