You may be thinking that you have a vintage car that you only use on sunny day weekends with a comfortable temperature outside; however, driving old cars you still have a need to dampen the rod noise or be able to listen all those classic tunes, not to mention keeping all that engine heat out of the passenger compartment of your car. The way to accomplish your goal of comfortable driving is to install the proper amount of car insulation in the correct places in your car’s interior.
One of the basic truths in insulating is that the thicker the insulation, the better it will insulate. However, car insulation is different from home insulation and R values are not a good measure of the efficiency of automotive insulating materials. You cannot put a foot or two of insulation in a car like you would in your attic. Therefore, car insulation is designed differently. Chemistry comes into play and creates a thinner and lighter type of insulation that can seal out noise and heat better than in a home.
For a comparison take a bowl full of marbles and a similar bowl full of sand. In the first instance you have a few dozen marbles with relatively large air spaces between them, as you might find in a house. In the second case you have thousands of beans packed tighter together with small air gaps between them. This denser material is like that used in cars. Automotive insulation is a chemical composite that converts vibration into silent energy in much the way shock absorbers convert dynamic motion into heat that is silent energy.
The Different Types Car Insulation Material
Let’s look at the characteristics of the most common types of automotive sound deadening material you can buy:
- Car mats – this is perhaps the most popular way of dampening sound inside a car. They are particularly great for covering panels and are excellent insulators as well, helping to keep the interior temperature regular. Plus, they are cheap and rather easy to install.
- Woven fiber and foam products – these are most often placed beneath the carpet and floor mats. Fiber cloths are not just good at absorbing noise; they are great at insulating as well. Foam is particularly great at dampening vibrations that emit from underneath the floor.
- Sound dampening sprays – dampening spray is a good alternative for places inside your car where matting cannot be used. This is the least used out of all the types of sound deadening methods.
The Base Material (For Car Mats)
Typically, sound deadening mats will have foil on the top surface and sticky material on the base. The base material determines how effective the mat is at deafening the sound and how well it will counter extreme temperatures. The two most common materials you will find on car mats are butyl and asphalt. These days a lot of manufacturers seem to prefer butyl over asphalt, and I can certainly see why. First, butyl products are more heat tolerant than asphalt ones, which I gather is due to the stronger chemical bonds between its molecules. In addition, asphalt tends to give off a rubbery odor while butyl mats do not carry a particular scent. One cause of this could be the relatively low melting point of asphalt.
Lastly, butyl is the lighter material of the two which makes for an easier installation process.
Car Insulation Chemistry
This is where the chemistry of sound comes in. By using different gas-filled molecular cell structures, the degree of noise and heat insulation can be increased without upping weight or increasing mass. Temperatures come into play, too. Mat Insulation materials type products operate better at higher heat ranges. This works well in a car where most parts are at temperatures above normal room temperature.
Better quality automotive insulation materials also rely on high performance lightweight insulation, used in conjunction with mat type insulation, to take advantage of a unique phenomenon. Researchers discovered that sometimes when different materials are combined, they perform better together than would be expected. The dissimilar materials benefit from something called bonding resistance or inner facial thermal resistance. Mat insulation also incorporates cell block technology to lock oil and water out of the cells and prevent them from being absorbed into the material as happened years ago with the moisture-trapping open-cell insulation used in older cars.
Spray On Car Insulation
Spray-on insulating materials are not currently promoted because of the experiences Detroit automakers have had with sprays a number of years ago. Sprays are production friendly in concept, but have proven to be inefficient, while adding weight and mass. Many companies note that no spray works as well as a constrained layer dampening material and sprays also do not reduce heat.
Car Insulation Thickness
Typically, mat type insulation will come in 1/8-, 1/4- and 1/2-inch thicknesses for use in different places in a car body. You might be able to fit 1/2-inch material under a roof or on the firewall, but 1/4-inch might be better to use on the floor. Again, the thicker the material, the better the insulation, but the material must fit the space. So, you must more or less map out the car and decide how thick a mat material to use in various places.
Measuring for Car Insulation
Most suppliers note that many people do not know how to measure the area of the panel they need to insulate. Unless a computerized pre-cut kit is available, it is bad practice to simply ask for enough insulation to do a ’50 Mercury. To determine the area, you must measure the height times the width and to express the area in square inches, you divide that number by 144. There are some guidelines, however. An early roadster will typically need 72 sq. ft. or two 36 sq. ft. bulk packs. An early coupe or roadster will require three bulk packs. A typical muscle car will use up 144 sq. ft. of insulation material in different thicknesses.
If you want to do only partial dampening to save money on materials, you can still get an acceptable improvement by insulating at least 30 percent of any panel. That will take the basic resonate vibration out of the panel, though it is not going to give you full noise reduction from outside sounds. Using this method, you would put the insulation in the center of the panel where you get the most dynamic motion and vibration. On a panel with an area measuring six square feet, you would need to use and least two square feet of a material.
Most car insulation suppliers have worked out several custom fit kits and say it is adding more of these each day. They are computer calculated for specific cars that get restored a lot like Camaros, Firebirds, Chevelles, muscle cars, some sports cars, and Volkswagens. The computer figures out what sizes and thicknesses each car requires and even cuts the patterns. You can lay a kit out on the floor, peel off the adhesive covering and simply stick the insulation in the proper place.
Roofs typically take thicker insulation (1/2 inch) and quarter panels are typically done with 1/4-inch material.
Whatever insulating material you use it is recommended to install in large sheets, such as covering a door panel with a bunch of small 12 x 12 sheets is poor practice. Larger sheets cover more area, require fewer seams and gaps and are easier to install. Larger sheets can also be trimmed smaller, but small sheets can’t be trimmed larger. The typical recommended sizes are 12 x 23 inches, 18 x 32 inches, 24 x 48 inches, and 12 x 36 inches for particular applications. Use only durable waterproof materials that are safe and do not support a flame. Check the internet for feedback on the supplier you use both for product quality, order fulfillment, shipping times and customer service.
Insulation In an Open Top or Convertible Car
Experts note that insulation in a door really helps in an open car. The inside of a car door is like a box that makes noise like a drum and has drain holes to let the noise out. If you insulate just the doors, the open car is going to feel more solid, be cooler and sound quieter. If you fully insulate it, you will know the difference immediately. “You don’t realize how much noise is in a car body until you start reducing it.”
Finally
All cars need insulation. All cars have insulation, although the amount and quality depend on the vehicle’s make and model. If you are like us, when you do a thing, you want it done right. But how do you decide if a thing is even worth doing in the first place since classic cars are not usually used as daily drivers? It is hard to rationalize paying for something you do not understand. Because we spend so much time in our vehicles, soundproofing a car is one of those things that can pay big dividends to your quality of life. Ironically though, it is also the kind of thing that when done right you will not see it or hear it.
Like with many things in life, automotive heat and noise insulation is one area in which it pays to be strategic and work smarter, not harder. There is no cure-all to create the vehicle of your dreams, and you should be wary of anyone trying to sell you one. The more you know, the more cost-effective you can be and the better results you will get when soundproofing your car.
