Climate Zones

Climate zones determine the severity of the weather and the duration of exposure to shingles. The climate can be a combination of hot and cold, dry, and humid. Each of these combinations will have different effects on shingle roofing.

In hot climates, shingles are exposed to intense heat for extended periods, causing them to expand and potentially become more susceptible to damage. On the other hand, in cold climates, shingles endure freezing temperatures, which can lead to contraction and increased brittleness. Dry climates may subject shingles to prolonged exposure to UV rays, which can degrade their protective layers and reduce their lifespan. In humid climates, moisture and humidity can promote the growth of algae, moss, and fungi on shingles, compromising their integrity.

Thermal Cycling

The term “thermal cycling” describes the process by which roofs become hot during the day and cool at night. All roof components, including the shingles, expand when they heat up and shrink when they become cold.

As shingles age, they undergo continuous cycles of expansion and contraction, gradually causing them to lose their original shape and size. This phenomenon is particularly true for organic shingles, which tend to be more susceptible to thermal cycling effects. Organic shingles are composed of felt or wood fiber mats, saturated with asphalt, and coated with protective granules. Over time, repeated thermal cycling can result in the shrinkage of organic shingles, affecting their overall performance and longevity.

Additionally, shingles that bridge the joint between two underlying shingles can be prone to splitting under extreme thermal cycling conditions. The constant stress from expansion and contraction can weaken the shingles’ structure, leading to cracks and potential water infiltration.

The more extreme the temperature differences, the greater the expansion and contraction of all roofing components. Roofs that are subjected to frequent and significant thermal cycling tend to be less stable and more vulnerable to damage. The continuous stress on the shingles and other roofing materials can accelerate their aging process and contribute to premature deterioration.

Several factors influence the amount of thermal cycling that shingles experience. The climate zone plays a crucial role, as regions with more significant temperature variations are more likely to experience intense thermal cycling. The number of shingles installed on the roof can also impact thermal cycling, as larger roofs with more extensive shingle coverage may experience greater expansion and contraction. The adequacy of ventilation in the attic is another important factor since proper airflow can help regulate temperature fluctuations on the roof. Moreover, the color of shingles can influence thermal cycling, as darker-colored shingles tend to absorb more heat and undergo more significant expansion than lighter-colored ones. Finally, the properties of the granule coating on shingles can affect their resistance to thermal cycling effects, with high-quality granules providing better protection against temperature-induced stress.

In conclusion, understanding the impact of climate zones and thermal cycling on shingle roofing is essential for maintaining the integrity and longevity of the roof. By considering these factors and implementing appropriate measures such as proper ventilation and choosing shingles suitable for specific climate conditions, homeowners can help mitigate the negative effects of thermal cycling and ensure the optimal performance of their roofs for years to come.

This post was written by Ted Williams! Ted is the owner of A Old Time Roofing, one of the best roofing companies in Saint Petersburg, FL! Ted is a Master Elite Weather Stopper GAF Roofing Contractor, a double award winner of Best Steep-Slope Contractor from GAF, and an achiever of Master Elite Consumer Protection Excellence from GAF. He has been serving the Pinellas County area since 1978. Old Time Roofing has a tradition of quality workmanship, servicing residential and commercial properties.


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