Condensation forms in roof spaces and can be severe. Water droplets can drip ontoinsulation material or the ceiling of the room below. If there are timber roof trusses (beams) then severe condensation will cause rotting of timber which could lead to wet rot or even worse dry rot. Good ventilation will stop the build up of moisture. Improper roof ventilation may dramatically lessen the life of a roof and void your shingle warranty. The shingle manufacturer has specific guidelines for the amount of ventilation you need based on attic square footage. Attic ventilation is very important as too little will literally cook your shingles; which, will cause them to be brittle and this will make susceptible to wind, hail and storm damage. Your utility bills may also suffer as the excess heat from your attic may radiate through your ceiling and cause your air conditioner to run excessively.