As a result, the ventilation of the attic has problem(the inside air temp is much higher than that of the outside; the best situation is when they are the same), thus water condensed on the inside of the roof and eventually the wood strips will decay. The requirement for attic vent sizing is nominally 1:300 (or one square foot of vent size for every 300 square feet of attic floor area). Some people even installed those turbine fan, or solar powered fans for a better result.
Add thicker insulation to the attic can help.
Add thicker insulation to the attic can help.