Temperature should be comfortable not only in main rooms, but also in the attic. Research shows that if exterior temperature is 108-112°F and interior is 68-72°F approximately, the temperature of vented attics is 106-110°F approximately. So, as we can see, the temperature of vented attics is very close to the temperature of exterior, but it is very different from interior temperature.
If we repeat this research with the same exterior and interior conditions, but in the unvented attic, the results will be different from previous research. The attic temperature will be less than 76-80°F, which is more close to interior temperature. It makes the attic more comfortable for people who live in the house.
Unvented attics have the comfortable air temperature even in extreme weather conditions. For example, if exterior air temperature in winter is -20°F, attic temperature will be 55-59°F. And if outside temperature is 114-116°F, air temperature inside of the attic will be 79-83°F approximately. So, unvented attics are comfortable even if the weather is too cold and if it is too hot. In addition, unvented attics don’t cause chimney effect and can reduce common moisture problems. Temperature is not the only reason to use spray foam insulation.