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American Idle
Layered up: Proper insulation makes a difference

By Jeff Barker
contributing writer

Just like in Johnny Cash’s song, “I’ve Been Everywhere,” after you have crossed the deserts bare and breathed the mountain air you know you’re going to run into extreme weather and you’d better hope your truck’s insulation is up to snuff.

Although some trucks have better factory-installed insulation packages than others, many of them were ordered with intentions to save on weight and cost and are insulated about as well as a port-a-pot.

Floorboards and firewalls

First, remember the basic science that heat rises. Engines and driveline components in modern trucks put off a lot of heat while they’re in operation, and the firewall and floorboards become heat-soaked after a while.

Where do you think that heat goes? Just touching the floor of your cab with a bare hand on a warm day will give you a quick answer. But there is a way to keep more of that intense heat out of your cab.

You will need enough automotive heat and sound insulation to cover the entire floor of your cab and sleeper, including inside the firewall and the floor of the storage area under the bunk. It is generally made of rubber underpadding and has an aluminum foil facing.

J.C. Whitney and other online auto parts retailers sell it by the roll in various widths and lengths. Be sure you get the 3/8-inch thickness. That’s thick enough to be effective but thin enough so you will still be able to remount everything without problems.

Then, break out those tools and get that factory floor mat out of the cab and sleeper. This will involve removing your seats, so bleed down the air pressure before even thinking about disconnecting those air lines. Once those are out, remove the shift boot bezel, door sill plates, and anything else in the way before you lift that mat out.

Once the mat is out, go fetch a few garbage bags and carefully remove and dispose of any old insulation, taking care not to disturb any wiring. Then, vacuum the floorboard thoroughly. Remove all of your stuff from your sleeper side boxes and go through the same process that you did with the floor.

If you want to reuse your floor mat, now is a good time to clean it thoroughly so it has some time to dry before reinstallation later.

Now, it’s time to take some measurements and prepare to install your new insulation into the cab floor. You will need a good utility knife with a sharp blade or a pair of tin snips. Try to cover as much floor area as possible. You will need to remove a section for your seat pedestals to mount and tighten down properly. Reinstall the floor mat and other accessories, and make sure all controls function properly afterward.

Look up and to the side

Unless you’re lucky enough to have a truck already equipped with what’s commonly referred to as an “Arctic” insulation package, there’s likely little to no insulation on the walls or in the roof of the sleeper. Adding insulation will help retain heat in the winter and keep out radiant heat coming in from the exterior walls and roof while being baked in the sun.

Using the same type of heat and sound insulation will work well. You do not want to use fiberglass insulation because it can cause skin irritation and normally isn’t as flame-resistant as rubber-based materials used in automotive applications. You will probably have to remove some cabinets and interior panels to apply spray adhesive to the surfaces to install it, so allow yourself some time to do this job right. Be sure to use a fan to draw the fumes out of the work area.

If you have a high-rise condo style sleeper with interior roof panels that can’t be removed easily, you may be better off having an RV-style roof vent fan installed to draw out radiant heat that builds up when you’re parked. Otherwise, you can remove the headliner and install insulation on the interior of the outside roof panel, covering as much area as possible.

While on the road, you will likely notice how much lower your interior noise level is after completing this project.

Parked for the night

Once you are on the road and decide to call it a day, think about those windshields and how much heat conductivity they provide for your truck’s interior.

You can place reflective sun shades in them to help keep the interior cooler. If your truck has a skylight window and/or side windows in the sleeper, cover them up.

If you have your truck parked in such a way that your hood isn’t vulnerable – parked nose in, for example – you can further reduce the heat transmitted to the cab interior by raising your hood.

This lets the engine heat rise upward so it doesn’t continue to heat-soak the firewall as much for several hours after you park and shut it off. LL

Editor’s note: This article is for information purposes only. If you’re not sure about performing the work yourself, it’s advisable to seek the help of a competent professional.

Jeff Barker is an OOIDA member and a former certified diesel mechanic. He can be reached at