The present invention generally relates to anchoring systems for insulated cavity walls, and more specifically, a thermally-isolating fastener that creates a thermal break in a cavity wall.
Anchoring systems for cavity walls are used to secure veneer facings to a building and overcome seismic and other forces (e.g., wind shear, etc.). Anchoring systems generally form a conductive bridge or thermal pathway between the cavity and the interior of the building through metal-to-metal contact. Optimizing the thermal characteristics of cavity wall construction is important to ensure minimized heat transfer through the walls, both for comfort and for energy efficiency of heating and air conditioning. When the exterior is cold relative to the interior of a heated structure, heat from the interior should be prevented from passing through to the outside. Similarly, when the exterior is hot relative to the interior of an air conditioned structure, heat from the exterior should be prevented from passing through to the interior. The main cause of thermal transfer is the use of anchoring systems made largely of metal components (e.g., steel, wire formatives, metal plate components, etc.) that are thermally conductive. While providing the required high-strength within the cavity wall system, the use of metal components results in heat transfer. Failure to isolate the metal components of the anchoring system and break the thermal transfer results in heating and cooling losses and in potentially damaging condensation buildup within the cavity wall structure. However, a completely thermally-nonconductive anchoring system is not ideal because of the relative structural weakness of nonconductive materials.
In one aspect, a thermally-isolating fastener for use in a cavity wall to connect a wall anchor to an inner wythe includes a fastener shaft having a screw portion including a driven end and an attachment portion opposite the driven end. A fastener head is selectively attachable to the attachment portion of the fastener shaft. The fastener head includes an internal portion and an external portion encasing the internal portion and configured to provide a thermal break in the cavity wall when installed.
In another aspect, an anchoring system for use in a cavity wall having an inner wythe and an outer wythe spaced from the inner wythe and forming a cavity therebetween includes a wall anchor configured for attachment to the inner wythe. The wall anchor includes a mounting surface configured for engagement with an exterior surface of the inner wythe and a receptor configured for engagement with a veneer tie. The wall anchor defines at least one mounting opening. At least one thermally-isolating fastener is configured to extend through the at least one mounting opening to attach the wall anchor to the inner wythe. The at least one thermally-isolating fastener includes a fastener shaft having a screw portion including a driven end and an attachment portion opposite the driven end. A fastener head is selectively attachable to the attachment portion of the fastener shaft. The fastener head includes an internal portion and an external portion encasing the internal portion and configured to provide a thermal break in the cavity wall when installed.
Other objects and features will be in part apparent and in part pointed out hereinafter.
Corresponding reference characters indicate corresponding parts throughout the drawings.
Referring to
Successive bed joints 30 and 32 are substantially planar and horizontally disposed and, in accordance with building standards, are approximately 0.375 inches in height in a typical embodiment. Selective ones of bed joints 30 and 32, which are formed between courses of bricks 20, are constructed to receive the insertion portion of a veneer tie 44. It is understood that the described and illustrated wall structure 12 is exemplary only. Other structures may be used without departing from the scope of the present invention. A wall anchor 40 is surface mounted on the inner wythe 14 and is supported by the inner wythe. As described in greater detail below, the wall anchor 40 is mounted on the inner wythe with thermally-isolating fasteners 48. The anchoring system 10 is constructed and configured to minimize air and moisture penetration around the wall anchor system/inner wythe juncture and limit thermal transfer.
For purposes of the description, an exterior cavity surface 24 of the inner wythe 14 contains a horizontal line or x-axis 34 and an intersecting vertical line or y-axis 36. A horizontal line or z-axis 38, normal to the xy-plane, passes through the coordinate origin formed by the intersecting x- and y-axes.
In the illustrated embodiment, the anchoring system 10 includes wall anchor 40, veneer tie 44, and an optional wire or outer wythe reinforcement 46. At intervals along the exterior surface 24 of the inner wythe 14, wall anchors 40 are mounted on the inner wythe 14. The wall anchor 40 includes a mounting face or surface 50 and an outer face or surface 52. The mounting face 50 is configured to be positioned adjacent the exterior surface 24 of the inner wythe 14. A pair of legs 42 extend from the mounting surface and are configured to penetrate the insulation 26. As installed, the mounting face 50 covers the opening formed by the insertion of the legs 42 into the insulation 26, thereby maintaining insulation integrity and precluding the passage of air and moisture through the openings formed by the legs. The wall anchor 40 includes a receptor portion 62 configured to extend into the cavity 22 and configured for engagement with the veneer tie 44. Wall anchors and veneer ties can be configured in other ways within the scope of the present invention
The wall anchors 40 are attached to the metal studs 17 with thermally-isolating fasteners or mounting hardware 48 that are configured to provide a thermal break in the cavity 22. Through the use of the thermally-isolating fastener, the underlying metal components obtain a lower thermal conductive value (K-value), thereby providing a high strength anchor with the benefits of thermal isolation. Likewise, the entire cavity wall obtains a lower transmission value (U-value), thereby providing an anchoring system with the benefits of thermal isolation. The term K-value is used to describe the measure of heat conductivity of a particular material, i.e., the measure of the amount of heat, in BTUs per hour, that will be transmitted through one square foot of material that is one inch thick to cause a temperature change of one degree Fahrenheit from one side of the material to the other (BTU/(hr·ft·° F.); or W/(m·K) in SI units). The lower the K-value, the better the performance of the material as an insulator. The metal components of the anchoring systems generally have a K-value range of 16 to 116 W/(m·K) (about 9 to 67 BTU/(hr·ft·° F.)). The thermally-isolating fasteners as described below greatly reduce the K-values to a low thermal conductive K-value not to exceed 1 W/(m·K) (about 0.58 BTU/(hr·ft·° F.)), for example about 0.7 W/(m·K) (about 0.4 BTU/(hr·ft·20 F.)). The term U-value is used to describe the transmission of heat through the entire cavity wall (including the anchor, the insulation, and other components), i.e., the measure of the rate of transfer of heat through one square meter of a structure divided by the difference in temperature across the structure. Similar to the K-value, the lower the U-value, the better the thermal integrity of the cavity wall, and the higher the U-value, the worse the thermal performance of the building envelope. The U-value is calculated from the reciprocal of the combined thermal resistances of the materials in the cavity wall, taking into account the effect of thermal bridges, air gaps and fixings. Several factors affect the U-value, such as the size of the cavity, the thickness of the insulation, the materials used, etc. Desirably, the use of anchor as described herein may reduce the U-value of a wall by 5% -80%.
The thermally-isolating fasteners 48 extend through mounting openings 54 in the wall anchor 40 to connect the wall anchor to the metal stud 17. In the embodiment illustrated in
The fastener shaft 62 includes a screw portion 64 having a first diameter and an attachment portion 66 configured for selective attachment to the fastener head 60. The screw portion 64 includes a driven end 68 configured to be driven into the stud 17 to mount the wall anchor 40 to the stud. The screw portion 64 can be a standard self-drilling screw, as is known in the art. The screw portion 64 can be stainless steel or other suitable metal, or can be a polymer coated metal screw. The screw portion 64 can include a thermal coating to reduce the thermal conductivity of the anchoring system, as described below. In the illustrated embodiment, the attachment portion 66 is a threaded stud extending from the screw portion 64 opposite the driven end 68 and configured for attachment to the fastener head 60. The threaded stud attachment portion 66 has a second diameter smaller than the first diameter of the screw portion 64. The attachment portion 66 can be made of the same material as the screw portion 64 (e.g., stainless steel, other suitable metal, or polymer coated metal). Although a threaded stud is illustrated, other configurations for the attachment portion are within the scope of the present invention.
Any part of the fastener shaft 62 (the screw portion 64, the attachment portion 66, the driven end 68) can include a thermally-isolating coating. In one embodiment, every part of the fastener shaft 62 includes a thermal coating to provide a thermal break in the cavity. The thermal coating is selected from thermoplastics, thermosets, natural fibers, rubbers, resins, asphalts, ethylene propylene diene monomers, and admixtures thereof and can be applied in layers. The thermal coating optionally contains an isotropic polymer which includes, but is not limited to, acrylics, nylons, epoxies, silicones, polyesters, polyvinyl chlorides, polyethylenes, and chlorosulfonated polyethylenes. Alternatively, the thermal coating can be a ceramic or ceramic-based coating including materials selected from lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, indium, scandium, yttrium, zirconium, hafnium, titanium, silica, zirconia, magnesium zirconate, yttria-stabilized zirconia, and derivatives and admixtures thereof. An initial layer of the thermal coating can be cured to provide a pre-coat and the layers of the thermal coating can be cross-linked to provide high-strength adhesion to the fastener shaft 62 to resist chipping or wearing of the thermal coating.
The thermal coating reduces the K-value of the underlying metal components which include, but are not limited to, mill galvanized, hot galvanized, and stainless steel. Such components have K-values that range from 16 to 116 W/(m·K). The thermal coating reduces the K-value of the fastener shaft 62 to not exceed 1.0 W/(m·K). Likewise, the thermal fastener reduces the U-value of the cavity wall structure. Preferably, the U-value of the cavity wall structure including the thermal fastener is reduced by 5-80% as compared to the U-value of the cavity wall structure including a fastener without the thermal coating described herein. It is understood that other factors affect the U-value, such as the size of the cavity, the thickness of the insulation, the materials used, etc. The thermal coating is fire resistant and gives off no toxic smoke in the event of a fire. Furthermore, the coating is suited to the application in an anchoring system with characteristics such as shock resistance, non-frangibility, low thermal conductivity and transmissivity, and a non-porous resilient finish. Additionally, the thermal coating can provide corrosion protection which protects against deterioration of the anchoring system over time.
The thermal coating can be applied through any number of methods including fluidized bed production, thermal spraying, hot dip processing, heat-assisted fluid coating, or extrusion, and includes both powder and fluid coating to form a reasonably uniform coating. A coating having a thickness of about 3 to 300 microns is optimally applied, and in one embodiment is about 127 microns. The thermal coating is applied in layers in a manner that provides strong adhesion to the fastener shaft 62. The thermal coating is cured to achieve good cross-linking of the layers. Appropriate examples of the nature of the coating and application process are set forth in U.S. Pat. No. 6,284,311 and 6,612,343.
Referring to
The internal portion 70 is positioned within the external portion 72 to provide a thermal break. The external portion 72 comprises a casing 80 configured to receive the nut 74 and washer 76 of the internal portion 70. The casing 80 preferably defines a standard hex head and is formed from a thermally-isolating material. Although any suitable material could be used, the casing 80 is preferably constructed of a material which, in addition to having low thermal conductivity (such as the materials described above), also has sufficient hardness and resistance to abrasion to allow the casing to be engaged by a driving tool (not shown) and used to drive the fastener 48 into a stud or wall. The internal portion 70 can be attached to the casing 80 in any suitable manner, such as by snap fit. Alternatively, the casing 80 can be over molded on the internal portion 70. The casing 80 preferably fully encases the internal portion 70, including particularly the washer 76, such that no part of the internal portion is exposed when the fastener head 60 and fastener shaft 62 are connected, thereby preventing metal-to-metal contact at the juncture of the fastener head and the anchor 40 when the fastener 48 is in use. The casing 80 preferably has a thickness selected to provide a thermal break in the cavity. Although shown and described as a separate structure, preferably the casing 80 can be a thermal coating molded onto the internal portion 70. In one embodiment, the entire fastener 48 can be coated after the fastener head 60 is attached to the fastener shaft 62.
The casing 80 reduces the K-value of the underlying metal components which include, but are not limited to, mill galvanized, hot galvanized, and stainless steel. Such components have K-values that range from 16 to 116 W/(m·K). The casing 80 reduces the K-value of the fastener 48 to not exceed 1.0 W/(m·K). Desirably, the use of fasteners as described herein may be able to reduce the U-value of a wall between 5% and 80%. Tests have indicated an improvement of about 30%-40%. The casing 80 is fire resistant and gives off no toxic smoke in the event of a fire. Additionally, the casing 80 can provide corrosion protection which protects against deterioration of the anchoring system over time.
As seen in
Although a folded wall anchor is illustrated in
In the embodiment of
In the embodiment illustrated in
The fasteners as described above serve to thermally isolate the components of the anchoring system, thereby reducing the thermal transmission and conductivity values of the anchoring system as a whole. The fasteners provide an insulating effect and an in-cavity thermal break, severing the thermal pathways created from metal-to-metal contact of anchoring system components. Through the use of the thermally-isolating fastener, the underlying metal components obtain a lower thermal conductive value (K-value), thereby reducing the thermal transmission value (U-value) of the entire cavity wall structure. The present invention maintains the strength of the metal and further provides the benefits of a thermal break in the cavity.
Having described the invention in detail, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims.
When introducing elements of the present invention or the preferred embodiments(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.
As various changes could be made in the above products without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.