Roofing Ventilation
The need for ventilation in roofs and attics became apparent after it was observed that moisture inside attics, caused by the phenomenon of condensation, was deteriorating a large portion of the roofing materials and in extreme cases the insulation of the ceiling. Adding to this grief, wet attics became the breeding place for a variety of fungi and moulds . From then, wet attics had become the nightmare of many house owners. If roofing ventilations were a fancy contraption in the early days, in the modern world they are an integral part of any roofing solution. And gladly, there are a handful of ventilation techniques available today that can be used to avoid the troubles caused by moisture and cold weather condensations. Some of them are 1.Soffit Vents 2.Ridge Vents 3.Roof Vents 4.Gable Vents 5.Power attic Ventilators 6.Hip Vents, etc.
Need for Ventilation
Ventilations ensure that roofing spaces are not completely insulated from outside atmosphere. This can avoid unnecessary condensation or moisture seepage from living spaces into attics (due to difference in water vapor pressure). Moisture infiltration into the attic can cause unnecessary deterioration of roofing materials and, in extreme cases, the ceiling insulation. The growth of fungi and moulds in the attic due to excessive moisture can further add to the trouble. Formation of ice dams, heat build-up, etc are only a few roofing issues that are caused by poor ventilation of roofing systems .
Types of Ventilations
As mentioned before, the choice of ventilations is determined by the type of roofing space a particular building has. For instance, buildings with flat roofs or cathedral ceilings have very small roofing space. These types of roofs commonly require more ventilations than attic type roofs . That is, with the decrease in roofing space, the need for multiple ventilations increases. Roofing ventilations are commonly classified into 1.Intake vents and 2.Exhaust vents. And depending on the roofing system, a variety of ventilation techniques are available for each of these categories. Of all the types of roofing ventilations available, to preserve the simplicity of this essay, we shall be discussing only 1.Soffit Vents 2.Ridge Vents 3.Power attic ventilators and 4.Hip vents.
Soffit Vents: Soffit vents serve as intake vents for the roofing system. And as the name suggests, they are installed at the lowest edge of the roofs (or soffits) . This ensures the free intake of atmospheric air into the roofing space (attic) which is then exhausted through an exhaust vent usually located at the roof assembly’s peak . This system, where the intake vents are located at the lowest edge and exhaust vents are located at the peak, aids the natural flow of air (due to convection) in the roofing space. There are mainly two types of Soffit vents 1.Continous Soffit Vents and 2.Individual Soffit Vents. For wider soffit roofs, both continuous and individual soffit vents can be used (where individual soffit vent is more suitable for comparatively narrower soffits). But in case the soffit area is not wide enough to house any of these vents, vented drip-edges are used.
Ridge Vents: They serve as the exhaust ventilation for a typical roofing system. And therefore, they are usually used in conjunction with soffit vents. The location of these vents, at the length of the ridge of a roof, aids the natural convection of air, that is, from the soffit vents to the atmosphere through ridge vents. The one drawback to this type of exhaust vent is that they won’t work all the time. Depending on the type of roofing systems, their functionality may vary. For instance, for roofing systems such as low pitch roofs, hip roofs, or roofs with multiple roofing sections, ridge vents are seldom used.
Power attic Ventilators: Their function is very similar to that of an exhaust fan. They are used to force air outflow from the attic space. As with other exhaust vents, powered attic ventilators are also best used in conjunction with soffit vents. And since these ventilators provide an additional push for the exhaustion of heated air, they will improve the air intake rate at the intake vents (soffit vents). Also, for improved air flow, they should always be located near the ridge of a roof. And it should always be ensured that ridge vents or static vents are not installed along with powered attic ventilators. This is because, as the forced air exhaustion caused by power ventilators will improve the air intake significantly, sometimes, ridge vents or static vents may also take part in air intake along with soffit vents. And by virtue of the location of these vents (ridge and static) this may cause moisture infiltration into the attic (roofing space) which negates the whole purpose of ventilation .
Hip vents: They have a similar functionality as that of ridge vents since they also serve as an exhaust vent that is best used with an intake vent located at the soffits or eaves. Hips vents are installed at the hip of a non-traditional roofing system (hip roofs). One benefit of using this type of vent is that they are almost unrecognizable from the ground. This is made by possible by using the shingle-over design. A possible drawback to this type of ventilation is water leakage during heavy precipitation. This attribute is very similar to that of ordinary ridge vents. But for hip vents, proper installation and using adequate vent materials can limit the amount of water leakage into the attic considerably.
Conclusion
Even though it is not mandatory that we use intake and exhaust vents in conjunction, best possible results are obtained by the integration of both. An expert installation of both intake and exhaust vents in a roofing system can ensure a sound air flow inside the attic. This is important in avoiding common roofing problems such as heat build-up, moisture, ice dams, etc. Ignorance in this field also can result in an augmented onslaught of roofing issues. For instance, using powered ventilations in integration with static vents or ridge vents can increase the risk of moisture infiltration rather than avoiding it. Similarly, ventilations are selected specifically for a particular roofing system while considering the peculiarity of the host building. It is essential that the installer understands the demands of a particular roof before going with a ventilation solution.
Bibliography
J. Montes. (2012, December 6). Different Types of Roofing Ventilation. Retrieved April 12, 2016, from Jmontesinc: http://www.jmontesinc.com/2012/12/06/different-types-of-roofing-ventilation/
NRCA. (2016). Everybody Needs a Roof. Retrieved March 12, 2016, from National Roofing Contractors Association: http://www.everybodyneedsaroof.com/roof-vents
Roofing Canada. (2003, February). Ventillation. Canada: Roofing Canada.
