Can a roof have too much ventilation?
Ventilation can be Difficult to Understand
Ventilation is one of the most misunderstood areas of roofing. Older homes did not require much or any ventilation because they tended to be more drafty and under-insulated. Because newer homes are sealed up tight and heavily insulated, ventilation becomes more important. Often little or no planning is done when addressing attic airflow. It is important that attics are ventilated correctly.
Hat Air Rises
Ideally, the best venting condition would be to have cold air from the eaves of the house enter the attic while hot air escapes out the ridge of the roof. Unblocked soffit vents or roof top soffit vents allow an opening for cold air to enter the attic. When hot air escapes through a ridge vent or power fan, it creates a suction that pulls the colder air through the soffits.
More is Not Always Better
People tend to think more ventilation is better, but it is more important to have balanced ventilation. Having two types of ventilation can work to prevent air movement. For example, if a power fan is installed on a roof with a ridge vent, the power fan will pull hot air from the ridge and stagnate the attic’s air movement. Ridge vents are more reliable than power fans because they have no moving parts and do not require electricity, but some roofs like hip roofs are better suited for a power fan due to their unusual shape.
Balanced Ventilation
The amount of ventilation needs to be proportional to the amount of intake and properly sized for the building. Following the Federal Housing Authority (FHA) 1/300 Rule we make sure that for every 300 square feet of enclosed attic space, 1 square foot of ventilation is present. The soffit and ridge vents need to be balanced in size for proper movement. If the ridge or soffit openings are much larger in total size, the system will not work correctly.
If you have more questions about what roofing ventilation is correct for your home call Bayside Exteriors at 302-200-7663
Author
Craig Cameron
Bayside Exteriors