It is important in modern buildings such as homes and offices that the attic space of the building be well ventilated. Attic ventilation reduces the searing heat that can build up in the attic during summer months, thereby reducing substantially the cooling costs and other problems associated with the attic heat. It is equally important that moist air be removed from the attic to reduce and control humidity, which otherwise can result in mold, mildew, and rot within the attic and living spaces. Removal of heat and humidity from attic spaces traditionally has been accomplished with attic ventilation systems of various designs. Such systems include, for example, simple gable vents to promote cross-ventilation through the attic, static roof vents located at strategic positions along the slope of a roof, and active attic ventilation systems, which usually include thermostats and/or humidistats that activate electric attic fans above a predetermined temperature and/or humidity. Static and active attic ventilation systems generally are used in conjunction with soffit or eve vents, which admit fresh outside air into the attic to replace the hot and/or humid air that is removed.
More recently, ridge ventilation or ridge vent systems have become popular for ventilating the attic space of a building. Ridge ventilation systems generally include a long opening known as a “ridge slot” cut along the apex or ridge or a gable roof through which hot air can escape the attic below as a result of natural convection. An elongated ridge vent extends along and covers the ridge slot and is designed to allow air to escape while preventing rain water and pests from entering the attic through the open slot. Early ridge vents were made of roll formed aluminum. Later ridge vent designs included lengths of corrugated or fibrous material that covered the ridge slot. Ridge cap shingles were applied atop these later ridge vent designs to cover them and provide a pleasant appearance.
More sophisticated ridge vents have evolved that generally are formed of injection molded plastic vent sections that are attached to the roof end-to-end along the ridge to span and cover the ridge slot. The vent sections generally have transversely flexible center panels flanked along their outside edges with vents covered by vent louvers. The center panel is held a short distance above the roof deck by depending stand offs or supports to maintain a space between the center panel and the roof. The vent louvers cover the vents to prevent pest infestation while permitting air to flow through the vents. Such ridge vents also usually are formed with upstanding wind baffles outboard of and spaced from the vents. The wind baffles generate higher velocity and thus lower pressure vortices or zones in the region of the vents as a breeze blows across the roof and over the wind baffles. This is known as the Bernoulli effect. These lower pressure zones help to draw air from beneath the ridge vent and thus out of the attic below. Once these ridge vents are installed, ridge cap shingles are applied over the top of the center panels to provide an aesthetically pleasing appearance. Many ridge vents are formed with weep holes located at intervals along the bottoms of the wind baffles to allow rain water to escape from the space between the vents and the wind baffles.
While the latter more sophisticated types of ridge vents have proven quite successful at ventilating an attic, they nevertheless are plagued with numerous problems and shortcomings inherent in their designs. For example, these ridge vents rely largely on natural convection or the rising of hotter air within the attic to achieve good ventilation. While this is reasonably effective for ventilating hot attics, it does not provide much ventilation of the moist humid air that can form in cooler attics where there may be little or no heat induced convection. Further, since the Bernoulli effect is generated only when a breeze blows across the wind baffles, these ridge vents become purely passive and rely exclusively on convection when the outside air is static and there is no breeze. Even when there is a breeze, its direction can effect the efficiency of ventilation. For instance, if the breeze happens to blow along the length of the ridge vent rather than across its width, the resulting Bernoulli effect is minimal and, again, the ridge vent becomes essentially passive.
Some attempts have been made to provide ridge vents with active supplemental ventilation to address problems such as those discussed above. These attempts include, for example, electric fans inside the attic that blow air up and out the ridge slots, electric fans in stacks extending upwardly from the ridge vent, and electric soffit fans that blow outside air into the lower regions of the attic thereby forcing attic air to exit through the ridge vents. Such attempts may be useful, but can be complex, cumbersome to install, difficult to maintain, and less effective than desired.
Accordingly, a need persists for a ridge ventilation system that addresses the problems and shortcomings of present systems. Such a system should provide efficient and effective attic ventilation under all wind conditions, including when there is no wind or when the wind direction coincides with the direction of the roof ridge. It should be capable of drawing moist humid air out of the attic even when the air in the attic is cooler and there is little or no heat induced convection to cause airflow. All of these functions and more should be accomplished with a system that is efficient, simple to install, virtually maintenance free, and highly reliable for many years. It is to the provision of such a ridge ventilation system that the present invention is primarily directed.