Thermal Expansion Factors in Guttering

Metals vary their shape, area and volume when their temperature rises. This phenomenon is due to kinetic energy agitating their molecules more, and thereby increasing their average separation. However, this expansion varies within limited temperature ranges, and depending on the particular metal.


Using the Coefficient of Thermal Expansion to Measure the Rate


The coefficient of thermal expansion expresses this increase in terms of fractional change per degree of temperature. Variations in the formula allow for volumetric, area and linear variations. However, the main takeaway for us is a higher coefficient indicates a greater expansion rate.

The coefficients of thermal expansion for aluminum, brass, copper, steel, and iron at 20º C are 24, 19, 17, 13, and 12 respectively according to HyperPhysics. Therefore, gutters made of these metals react differently to temperature changes.


Thermal Expansion in Action: Bi-Metallic Strips


If we were to join two metals, say steel and copper along their entire length and warm them, then the strip would bend away from the copper as this expanded at a faster rate.

These bi-metallic strips help mechanical clock mechanisms keep accurate time. They are present in many mechanical thermostats, and make accurate dial thermometers. Finally, we find them in heat-sensitive circuit breakers and other applications.


How Thermal Expansion Affects Eavestroughing Too


Let’s assume we attach an aluminum eavestrough to a row of wooden rafters appearing at the lowest point on a roof. Timber has low conductivity and thermal expansion. Hence we assume it has a coefficient of thermal expansion of zero for the purposes of this discussion.

However, the aluminum gutter has a relatively high expansion coefficient as we mentioned earlier. It follows that it may buckle in the summer unless the installer allowed for this in their design.

We have seen this happen to 80′ lengths, especially those installed in the cold of winter. Conversely, an eavestrough installed on a hot summer day may develop leaks at joints in winter, as it contracts.


This Is Yet Another Reason to Choose a Contractor Carefully


Not all contractors are equally knowledgeable in our industry. Some, like Valiant Exteriors have a depth of experience and understand the materials with which they work. We have accumulated extensive knowledge down the years. When you hire Valiant Exteriors to install your eavestroughs, this expertise is included in the price.

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Bi-Metallic Thermostat Coil: Shorenster  BY CC 3.0

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