Re-roofing over an existing layer of shingles can reduce the ability of the newer shingles to resist damage from _______.

Re-roofing over an existing layer of shingles can reduce the ability of the newer shingles to resist damage from hail due to several factors. When multiple layers of shingles exist, the thickness of the system increases, which can impair the performance of the top layer during hail impacts. The additional layer can absorb some of the energy from the hail, but it can also increase the risk of damage to the new shingles because they may not be able to flex or respond effectively to the impact under the added weight and structure of the older shingles.

Moreover, the existing layer may retain moisture and debris, which can compromise the bonding and effectiveness of the newer shingles. Consequently, hail, which is known for producing sharp and forceful impacts, can more easily penetrate or crack the new layer, making it less effective overall in resisting damage.

The other weather-related elements, such as rain, snow, and sunlight, do not compromise the structural integrity of roofing materials in the same manner as hail. While they can contribute to degradation over time, it is specifically hail that poses a significant risk of damage under the conditions created by multiple shingle layers.