Patent Application
20080113612
This invention relates generally to attic ventilation systems and more specifically to ridge vents.
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.
Briefly described, the present invention, in one preferred embodiment, comprises an impeller exhaust ridge vent designed to extend along and cover an open ridge slot along the ridge of a roof. The ride vent includes a laterally flexible central panel having edge portions and a width sufficient to span and cover the ridge slot. Depending standoffs or supports can be formed on the bottom of the central panel for supporting the central panel above and spaced from the roof deck. A base panel spaced from the central panel may be provided to cover the roof deck and form a smooth substantially sealed air duct between the base panel and the central panel. Vents are thereby formed along the edge portions and vent louvers cover the vents to allow air to escape from beneath the central panel while inhibiting debris and pests from entering. Upstanding wind baffles are disposed outboard of and spaced from the vents and extend along the ridge vent to define a trough between the edges of the central panel and the wind baffles. At least one tangential impeller has a plurality of impeller blades and is rotatably mounted in the trough with its axis of rotation extending generally along the length of the ridge vent. The tangential impeller combined with the edge of the central panel on one side and the upstanding wind baffle on the other form a “cross-flow fan” adjacent the vent. Rotation of the tangential impeller creates a displaced stable vortex according to the principles of cross-flow fan operation. The displaced vortex, in turn, causes air to be drawn from beneath the central panel, and thus out of the attic through the ridge slot. The air is then exhausted, also according to the principles of cross-flow fan operation, up and away from the trough in which the impeller is mounted. Accordingly, the rotating tangential impeller transforms the otherwise passive ridge vent into an active ventilation system that forcibly draws air out of the attic below.
In one embodiment, the tangential impeller is mounted for free rotational movement within the trough. With this embodiment, the force of a breeze blowing across the roof and over the ridge vent causes the tangential impeller to spin, thus generating the active suction of air from the attic. In another embodiment, the tangential impeller is coupled to a small electric motor, which rotates the tangential impeller when activated. The electric motor can be powered by any suitable source of electricity such as, for example, the building's electrical service, a solar panel, batteries, a wind generator, or combinations thereof. In any event, activation of the electric motor preferably is controlled by a controller that receives signals from temperature and humidity sensors within the attic. The controller is configured to activate the electric motor, and thus to spin the tangential fan, upon the occurrence of predetermined temperature and humidity conditions within the attic. With this powered embodiment of the invention, air can be forcibly drawn out of the attic without regard to the presence of an outside breeze or the presence of hot attic air to drive convection based ventilation. Thus, efficient ventilation can be accomplished when there is no breeze or when the breeze happens to be blowing along the length of the ridge vent. Equally importantly, attic ventilation can be achieved under conditions where passive ridge vents provide little or no ventilation. For example, if the attic air is too cool to drive convection based ventilation, but it nevertheless is desirable to ventilate the attic because of high humidity conditions therein, the motor of the present invention can be activated to draw the humid air out of the attic through the ridge slot. Other conditions may exist in which active ventilation can be accomplished with the present invention under circumstances where natural ventilation might not otherwise occur.
Thus, a novel new ridge vent is now provided that successfully addresses the problems and shortcomings of prior art ridge vents discussed above. These and other features and advantages of the present invention will become more apparent upon review of the detailed description set forth below, when taken in conjunction with the accompanying drawing figures, which are briefly described as follows.
Referring in more detail to
A vent 28 is formed along the edge portion 23 of the center panel 21 to permit air to escape from beneath the center panel. Preferably, the vent 28 is covered by vent louvers 29 to prevent pests and debris from passing through the vent 28 and entering the attic through the ridge slot 16. The vent louvers 29 can take on any appropriate configuration, but are shown in
According to the present invention, one or more impellers 41 are disposed in the trough 32 and are rotatably mounted therein for rotation about an axis that extends along the length of the trough. In the preferred embodiment, each impeller is of the generally elongated cylindrical type having a plurality of radially arrayed, spaced apart, and axially extending impeller blades 44 (
Preferably, the impellers 41 are sized and mounted so that a portion of each impeller projects upwardly above the top edge of the wind baffle 31 and above the edge of the center panel 21, for purposes described in more detail below.
Operation of the impeller exhaust ridge vent of this invention is described in detail below in conjunction with the remaining drawing figures. In general terms, however, the tangential impellers in conjunction with the adjacent edge of the center panel 21 on one side and the wind baffle on the other form a classic cross-flow fan. Rotation of the impellers within the troughs generates, according to principles of cross-flow fan operational, a stable vortex within the trough with the stable vortex being displaced toward the edge of the center panel. The stable vortex, in turn, creates a relatively lower pressure zone outboard of the vortex, which causes air to be drawn forcibly from beneath the center panel and ejected from the trough. Thus, the ridge vent of this invention becomes an active ventilation system upon rotation of the tangential impellers and forcibly draws attic air out through the ridge slot and exhausts the air from the troughs of the ridge vent. In one embodiment, the tangential impellers 41 are mounted for free rotation within the trough. The force of a breeze blowing across the roof ridge causes the impellers to spin, thus drawing air from the attic as described. In another embodiment, the tangential impellers are driven by a small electric motor, the electric power for which may originate from the buildings electrical service, from solar cells, batteries, or even wind generators, or combinations thereof. This later embodiment has advantages over the free rotating impeller embodiment because the impellers can be spun to draw air from the attic under any conditions, such as at night when convection driven ventilation through passive vents otherwise is minimal.
According to the present invention, a pair of tangential impellers 41 are rotatably mounted in the trough 32 and extend partially along the length thereof. In the illustrated example, the tangential impellers are mounted by means of axles 43 that are rotatably journaled within corresponding holes formed in buttresses 34. However, other mechanisms for mounting the impellers within the trough are possible and contemplated by the present invention. Such mechanisms may include clips or fasteners with which an impeller unit cam simply be snapped or attached within the troughs. In the illustrated embodiment, the axle 43 on the left in
The controller 57 is appropriately programmed to monitor the signals of the sensors such as temperature sensor 59 and humidity sensor 61 and to activate and deactivate the electric motor 56 to spin the tangential impellers based upon predetermined conditions. The spinning of the impellers, in turn, actively draws air out of the attic and exhausts it to the atmosphere due to the cross-flow fan effect, as discussed above. It may be determined, for example, to activate the impellers when the attic temperature rises above a certain minimum temperature to draw more hot air out of the attic than is vented by passive convection. It may further be determined to activate the impellers upon the occurrence of combinations of conditions, such as, for instance, when the attic temperature is to low to generate significant convective ventilation, but the humidity within the attic is above a selected threshold indicating that the attic requires ventilation to lower the humidity. Other conditions may dictate activation of the impellers as well. For example, the impellers might be operated on a time schedule or when there is no ambient breeze or when the ambient breeze is blowing along rather than across the roof ridge. These and other conditions and rules for operating the tangential impellers to draw air out of and ventilate the attic are possible and all such conditions and rules are contemplated and intended to fall within the scope of the present invention.
As previously mentioned, the tangential impeller 41 is formed with an array of impeller blades 44 (
The embodiment of
A prototype of the impeller exhaust ridge vent shown in
As can be seen from Table 1, a lateral breeze blowing across the roof ridge and across the prototype ridge vent of the present invention indeed results in significant rotation of the tangential impellers mounted in and extending along the troughs of the ridge vent. For example, impeller rotation of 15 rpm began to occur in this test when the air velocity measured at the vent ridge line was about 436 feet per minute (about 5 miles per hour). As expected, higher wind velocities resulted in higher rotation rates of the impellers with a wind speed at the vent ridge line of 1078 feet per minute (about 12.2 miles per hour) resulting in impeller rotations of 511 rpm on the leading edge of the prototype ridge vent and 386 rpm on the trailing edge. Accordingly, an embodiment of the present invention with free rotating impellers experiences substantial impeller rotation in moderate breezes across a roof.
The invention has been described herein in terms of preferred embodiments and methodologies that are illustrative of the invention and that are considered by the inventors to represent the best mode of carrying out the invention. However, the illustrative embodiments are presented only as examples of the present invention and are not intended to be limiting an any respect. In this regard, many additions, deletions, and modifications might be made to the illustrated embodiments by skilled artisans within the bounds of the invention. For example, while tangential impellers have been illustrated and discussed herein, other types of fans and fan technology might be used to enhance airflow, as may various fan blade configurations. The configurations of the trough and surrounding structures also may be modified or certain structures may be eliminated without destroying the impact and effect of the impeller exhaust ridge vent of this invention. These and other modifications might well be envisioned and implemented by those of skill in the art without departing from the spirit and scope of the invention as set forth in the claims.
