Roof Mounting Standoff
A new mounting system for elevating and supporting objects such as solar panels is disclosed. The mounting system is designed for attachment to new or existing roofs of a variety of constructions. Sealing features are incorporated into the mounting system so that additional separate flashing components are not required. The system requires only one bolt for attachment. The design is quick and simple to install, reducing the amount of time and labor required.
This application claims priority benefit of U.S. Provisional Application No. 61/547,860, filed on Oct. 17, 2011, which is hereby incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION Field of the InventionThe present invention relates to mounting system, and more specifically to a roof mounting system for photovoltaic power modules.
With the high cost of energy, it has become increasingly desirable to provide renewable energy sources for buildings. Photovoltaic modules are often mounted on roof tops to fulfill this need. Roof attachment structures for photovoltaic power systems are an often-overlooked aspect of system design and system cost, but the roof attachment system is in fact one of the most important aspects in terms of liability, e.g., in the event of water leakage or the loss of structural integrity. Additionally, roof attachment is the most labor-intensive step in the installation of a photovoltaic power system, and, therefore, improvements in the ease of attachment will have a great impact on the total life cycle cost of a system.
With these needs in mind, the present inventors have set out to develop an improved roof mounting system, which will be described below. It is believed that, compared with earlier systems, the structure of the present invention confers several advantages. For example, it is easier to install and less susceptible to water damage.
U.S. Pat. No. 6,360,491 relates to a roof support system for a solar panel. The mounting base in U.S. Pat. No. 6,360,491 does not provide any sealing features and therefore requires additional separate flashing components.
U.S. Pat. No. 5,603,187 relates to a watertight system for mounting equipment on roof. The mounting base in U.S. Pat. No. 5,603,187 requires multiple mounting bolts and does not provide any sealing feature, thus requiring additional separate flashing components.
The Unirac U-RS Series is also typical of the prior art and requires multiple mounting bolts and separate flashing.
The Zilla Metal Roof Standoff by Next Generation Energy requires separate flashing components.
BRIEF SUMMARY OF THE INVENTIONThe present invention is a structure for mounting and supporting objects such as photovoltaic modules on a roof. The mounting system is designed for attachment to new or existing roofs of a variety of constructions. The attachment is via one bolt instead of several thus reducing the number of roof penetrations. Sealing features are incorporated into the mounting system so that additional separate flashing components are not required. The design is quick and simple to install, reducing the amount of time and labor required.
The novel and unobvious features which are believed to be characteristic of the invention, together with further objects and advantages thereof, will be better understood from the following description considered in connection with the accompanying drawings in which a preferred embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention.
The present invention is a structure for mounting and supporting objects such as photovoltaic modules on a roof.
In the case of composite shingle roofing 29, such as in
The foregoing detailed description is illustrative of a preferred embodiment of the invention, and it is to be understood that additional embodiments thereof will be obvious to those skilled in the art. The embodiments described herein together with those additional embodiments are considered to be within the scope of the invention.
Analysis Of Pull Out Strength for the Wood Screw:The “withdrawal loads” or “pull out loads” of wood screws inserted into side grain (as opposed to end grain) of seasoned wood is:
P=15,700*Ĝ 2*D*L*F/M
- P=pull out strength
- G=specific gravity of wood
- D=shank diameter of screw, inches
- L=length of screw engagement, inches
- F=adjustment factors such as load duration factor, wet service factor, temperature factor, end grain factor, we use 0.7 here based on M=safety margin of 2.
The equation applies to screw pilot holes diameter=<70% of thread root diameter for softwood. Specific gravity is based on ovendry at 12% moisture content.
As an example of the above, for a 0.25″ wood screw threaded into fir. the G=0.31 (lowest of all varieties). The pull out strength per inch of screw engagement P=132 pounds per inch of screw engagement.
Analysis of Pull Out Strength for a Metal Roof:The pull-out strength of the screw connection is highly depending on the design of the “riv-nut” insert and the metal structure the riv-nut it attaches to. In most cases you can make it work by adjusting the following features:
- 1. Use a larger riv-nut to spread the tear-out load on the metal member.
- 2. Use a riv-nut with a stronger material.
- 3. Use a riv-nut with a longer thread length.
If the proper riv-nut is selected, the weakest link in the fastening system is on the metal structural member. In that case the pull out strength P would be:
P=0.6*S*PI*D*T*F/M
- P=pull out load
- S=ultimate tensile strength of metal member PI=pi or 3.14 D=flange diameter of riv-nut T=thickness of metal member F=adjustment factor, use 0.7 here M=factor of safety, use 2 here
For example, if S=50,000 psi for mild steel, D=0.5″, T=0.06″. Then, P=990 pounds, which is much lower than the 0.25 stainless fastener used in this example but still much better than a same size wood screw threading into wood beams.
EXAMPLES Static TestingA significant enhancement to the technology of post-roof interfacing is achieved through the use of an o-ring in the device. The o-ring provides an effective water seal at the interface without the use of additional caulking or sealing.
The integrity of the o-ring seal against leakage was tested by using a post for mounting a panel and by attaching the post of the invention to the bottom of a galvanized steel basin, simulating attachment to a metal roof for to metal flashing. No other sealing methods were employed. The basin was then filled with water to a depth of approximately one foot. This provides a constant pressure of about 0.4 psi across the surface. Since no other sealing method is used (e.g., using silicone, grease or wax), there is no non-polar electrostatic resistance or glue barrier to capillary intrusion by water into the joint. Only joint pressure applied on the o-ring will resist water intrusion. After several months in this condition, the assembly showed no signs of leakage.
Dynamic TestingTo test post-roof joint integrity under dynamic conditions, two posts were installed in tandem in a galvanized basin and fastened through into a wood joist to simulate a wood-framed roof. The posts were sealed at the basin interface as recommended for permanent installations using both the o-ring and a fillet of silicone caulking. The basin was then filled with water. The posts were connected at the top with a joist, and through a moment arm attached to a motor-driven cam, the assembly was set to rock in a periodic motion at about 40 cycles/minute. This tests four failure points simultaneously: pullout of the fastening into the roof, pullout of the fastening in the post, seal against leakage at the interface, and resistance to leakage or failure due to flexing or distortion of the roof surface.
The set up has completed over 500,000 cycles with no interface or leakage failure. It should be noted that the cross-braces which were nominally attached to each side of the wood joist have worked loose, but the joist itself, bolted through the basin into the posts, has not. While this was not a principal point of testing, it might be inferred that continuous stresses on a roof transmitted through the post system of the invention may cause the roof structure to fail before the post interface will fail.
It is to be understood that both of the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the invention as claimed.
Claims
1. A device for mounting a panel or other object on a supporting structure, said device comprising an elongated metal bar member having two opposed ends, each of said ends being centrally bored to provide two separate inwardly extending aligned channels each with an inner and outer end, the inner end of each channel being sealably closed by common separating wall means constituting part of the bar member such that said channels terminate adjacent each other but are separated therefrom, the outer end of one of said channels including means for fixing thereto the object to be mounted, and means including a screw thread fixed within the other channel and extending outwardly therefrom to affix the device to said supporting structure.
2. The device of claim 1 wherein the bar includes means to facilitate turning the device to affix the same to said supporting structure.
3. The device of claim 2 including an O-ring fixed into the end of said bar member surrounding said screw thread to facilitate sealing of the device against the supporting structure.
4. The device of claim 3 wherein the same end of said bar member that includes the o-ring further includes a cavity for housing a sealant, said sealant serving to facilitate further sealing of the device against the supporting structure.
5. The device of claim 1 wherein the object to be mounted is a photovoltaic module.
6. The device of claim 1 wherein the supporting structure is a roof-deck.
7. The device of claim 1 wherein only one bolt is used to affix the device to the supporting structure.
8. The device of claim 1 wherein no separate flashing components are required to provide a watertight seal.
9. A mounting system for mounting objects above a roof-deck, said mounting system comprising:
- a cylindrical body having a top end and a bottom end, the bottom end comprising a circular outer groove and an inner cavity;
- a threaded bolt engaged with and projecting in the same direction from said cylindrical body;
- wherein the circular outer groove is designed to house an o-ring which makes contact with the roof-deck to form a first seal;
- wherein the inner cavity is designed to house sealing caulk which makes contact with the roof-deck to form a second seal;
- wherein only one bolt is used to attach the mounting system to the roof-deck,
- wherein the first and second seal are sufficient to provide a watertight seal, and
- wherein no separate flashing components are required to provide a watertight seal.
International Classification: E04B 1/38 (20060101); E04D 13/18 (20060101);