The amount and type of precipitation, temperature and wind are the aspects of climate that should most affect the design and selection of the roof system for a building.
A building located in a dry climate like the desert southwest does not need the same type of roof as a building subjected to daily rains like in the pacific northwest. Places that have high fees for wastewater removal may want to consider a vegetated roof to absorb stormwater. However, rain isn't the only consideration. Snow can drift and collect in corners, topping flashings and cause leaks. Hail can puncture the roof system, requiring a roof that can withstand abuse. If there is a wide temperature spread between winter and summer, a roof system that will expand and contract with thermal movement is a good choice.
Climate also affects the amount of insulation needed. Predominantly hot areas should consider a reflective roof system to save on cooling costs. In mostly cold climates, energy savings depend on the cost of heating energy compared with cooling, the slope of roof, insulation, and overall building dimensions. One resource to determine whether a roof will have energy benefits is the Department of Energy's Roof Savings Calculator. Heat sinks may also be considered for hot climates to lessen the amount of thermal shock that can occur when a roof is suddenly cooled during a rainstorm.
Identifying the wind uplift requirements is important in areas prone to hurricanes or other high wind events. Anywhere the wind gusts more than gale force should take wind into consideration (even a 40-mile-per-hour wind can cause a poorly attached roof to peel).
Tomorrow we will discuss considerations for selecting the right roofing products from the building owner's perspective.
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