Poor attic ventilation and Insulation: Making sure that your attic is properly ventilated is very important, the three common styles of attic vents are ridge, soffit, and gable vents. The most effective vents are ridge vents that run the length of your roof ridge that let the rising heat escape from the attic. Having improper ventilation in your attic will cause your house to sweat more than it should and cause extra condensation around your wood beams and rafters and rot them away as well as cause mold which can spread down to your ceilings and can be very toxic. Poor insulation can be very similar to inadequate ventilation as well as causing less efficient heating and cooling inside your home. Insulation especially that is missing around the soffits can be hazardous because this can allow ice dams to build up in the winter months and as freeze/thawing occurs the shingles can be lifted and damaged, also as the ice melts slowly the water can easily be pushed up under the shingles and seep into your attic.