Aluminum Thermal Properties

By Jason Erickson, Operations Manager

Product research is an important part of the shopping process. One question we get over and over again, Is the Weatherwell Elite aluminum product hot to the touch?

Aluminum is beginning to be used more now by homebuilders in outdoor spaces as the need for sustainable materials continues to increase. Aluminum decking, railing, and shutters are some of the areas that are on the rise. There have been several comparisons relating to surface temperature between wood, composite, and aluminum done by different manufacturers. One such test can be seen in the attached video.

I just want to take a few moments to explain a little bit as to why we see the results in the this video. Let’s begin with identifying the properties that are involved which are thermal conductivity and specific heat. Thermal conductivity, simply put, is the speed at which heat moves through a material. Specific heat or heat storage capacity determines the amount of heat energy that the material can hold.

Materials with a high thermal conductivity will transfer heat at a high rate and those with a low thermal conductivity will transfer at a lower rate. This is why highly thermal conductive materials are used as heat sinks, like you find on computer or electronic components. Those with a lower conductivity are used widely as insulators. For instance aluminum has a conductivity value of 205 at room temperature whereas wood materials and polycarbonate/polyvinylchloride (PVC) have a range of .12 to .22. So, of course, aluminum is going to “heat up” much fast than the others. Just because it heats up faster does not necessarily mean it will be “hotter”. Let’s keep going.

Let’s take a look at how the specific heat value affects the material. Aluminum has a heat capacity (.9) approximately half that of wood (1.7). This means that it takes less heat energy to raise the temperature of aluminum than it does for wood. At the same time it takes less energy to “cool down” the aluminum. Aluminum, with the lower specific heat, stores or holds less heat energy thus allowing it to feel cooler.

Now let’s go back to video. Since the aluminum has less mass for the heat to move through and based on the properties above we can see why the aluminum will have a slightly lower surface temperature than that of the wood and composites. Also the lighter the color of the material plays a big role in the surface temperature as well. So just because it is a metal does not always mean it is going to be extremely hot.

The short answer for your customers, aluminum is less hot to the touch than wood or PVC materials. Sounds crazy right, but when you break down the thermal properties of these materials, you see why aluminum is continuing to gain popularity among builders and homeowners!

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