Moisture can accumulate and damage your roof and paint, proper ventilation can provide protection
During the past few years, homeowners have become increasingly aware of the energy savings afforded by properly venting their roof cavities. On hot summer days, the temperature inside a roof space can reach well over 60 degrees, putting additional strain on the cooling system. The use of soffit vents and ridge vents to ventilate the roof space has been well advertised. In addition to the energy savings, a properly ventilated roof can also help protect your paint.
Without the proper ventilation, hot moist air can be trapped inside a roof space. Moisture build up in fascia boards, soffits, and external cladding can contribute to mildew growth. In addition, the moisture accumulation can force paint off of a wood surface as it attempts to escape. Exterior sources of moisture (e.g. rain or sprinklers) can be controlled by caulking, painting or otherwise sealing exposed areas (It is important to regularly inspect all caulk for signs of failure.)
Controlling exterior sources of moisture is crucial for preventing wood rot, premature paint failure and other damage. Interior sources are much more difficult to control and are potentially much more damaging. Moisture generated within the home-from cooking, bathing, washing, etc.- the moisture must be provided a path to escape. Such moisture will seek the path of least resistance. If venting is insufficient, the moisture will migrate through walls and ceilings. If the moisture reaches the exterior of the house, it can become trapped between the paint film and the substrate, resulting in premature paint failure. This moisture can force the paint film away from its substrate, resulting in bubbling, cracking and peeling. This is most apparent on soffits and fascia. Experts advise that you should have approximately one square inch of venting evert sum meter of roof space. This venting should be evenly distributed between the soffit and the ridge. While adequate ventilation is most often discussed in relation to its beneficial effects on roofing materials and energy costs, proper ventilation can also help extend the life of paint.
Another issue which is commonly raised, is the topic of sealing of horizontal weatherboards. This exercise in itself can lead to paint failure do to moisture building up inside of the wall cavity and not having a sufficient ventilation system ( the weatherboard overlaps ). By sealing the weatherboard overlaps the moisture has essentially been trapped inside of a barrier between inside paint coating and exterior paint coating, It will only be a matter of time before the moisture ingresses into the timber and will lead to water rot, mould and quiet possibly paint failure in the form of localised paint blistering or peeling.