Patent Application
20070094964
Recent improvements in the construction of homes and buildings have resulted in the fabrication of highly energy efficient structures. New construction materials, improved construction methods, and more stringent local and state building codes have all combined to provide highly energy efficient structures. In particular, exterior walls that are insulated and sealed, made according to code, and with the latest construction materials, increase the energy efficiency of these structures.
Insulated and sealed wall structures (i.e., “airtight” structures) reduce heat loss by substantially preventing drafts that remove heat from the wall structure. In addition, insulated and sealed wall structures are constructed to prevent the passage of moisture through the wall. Thus, insulated and sealed walls are airtight and moisture resistant, and are highly energy efficient. However, since insulated and sealed walls do not “breathe,” breached or damaged insulated and sealed walls can harbor moisture and provide nearly ideal breeding grounds for mold and bacteria.
In addition, environmental climate changes can create temperature differences between the internal and external spaces of the insulated and sealed walls that can contribute to the formation of condensate on interior surfaces of the walls. For example, during northern cold winter months, the air outside of an insulated and sealed wall is cold and dry, and the air inside of the wall is warm and humid. Thus, a natural humidity gradient is formed where moisture vapor in the air of an interior of the wall structure naturally migrates to the exterior of the wall structure. Thus, large gradients in outside and inside air temperatures can lead to an accumulation of moisture within even an insulated and sealed wall.
The opposite conditions occur during the summer months, when the air outside the structure is warm and humid, and the air inside the structure is conditioned to be cooler and dryer. Thus, during summer months a natural gradient exists driving warm humid air toward an interior of an insulated and sealed wall. Consequently, moisture can accumulate within an insulated and sealed wall due to normal, climate-induced temperature and humidity gradients.
Moisture includes bulk liquid, such as rain or rain droplets, and moisture vapor, such as in warm and humid air. Moisture, whether bulk or in the form of moisture vapor, can accumulate on surfaces of an insulated and sealed wall, as described above. In some cases, moisture is the result of natural condensation, but may also be the result of wind driven water that enters the wall along a window or door seam. For example, forming a window or a door in an exterior wall provides locations where water can enter the wall assembly and accumulate behind the wall covering. In some cases, moisture entering in the form of water is the result of poor workmanship, or alternately, a deterioration of flashing or sealants around the window/door.
In general, moisture accumulation within a wall, whether in the form of bulk liquid or in the form of moisture vapor, structurally damages the wall and can lead to health and safety issues for the occupants of the structure. In particular, moisture within a wall is known to create a breeding ground for insects, and can form other health hazards, such as the growth of molds and/or bacteria. The deleterious effects of moisture accumulation within a wall are accelerated in hot and humid environments.
This undesirable moisture penetration and accumulation within a wall assembly in new building structures has created challenges for the construction and insurance industries. Thus, there is a need for a system and a method to prevent moisture from accumulating in a sealed exterior wall assembly of a building structure, and for the removal of moisture that potentially collects within an exterior wall assembly.
One aspect of the present invention is related to a dynamically ventilated exterior wall system. The dynamically ventilated exterior wall system includes a sealed exterior wall assembly and a ventilation assembly fluidly coupled to the exterior wall assembly. The sealed exterior wall assembly includes an interior wall portion and an opposing exterior wall portion, and insulation and a flexible porous grid disposed between the interior and exterior wall portions. The ventilation assembly includes a head end unit coupled to at least one air supply conduit and at least one air return conduit, where each of the conduits communicates with the porous grid of the exterior wall assembly. The head and unit is configured to supply conditioned air through the air supply conduit(s) to the exterior wall assembly and remove humidity from the exterior wall assembly through the air return conduit(s).
Another aspect of the present invention relates to a method of dynamically ventilating a sealed exterior wall that includes an interior wall portion and an opposing exterior wall portion and insulation adjacent to the interior wall portion. The method includes disposing a porous grid between the insulation and the exterior wall portion to define an air space within the sealed exterior wall. The method additionally provides supplying conditioned air through the air space. The method ultimately provides for removing humidity from the air space.
Another aspect of the present invention relates to an exterior wall system. The system includes an exterior wall assembly and means for transporting moisture out of the exterior wall assembly. The exterior wall assembly includes an interior wall portion and an opposing exterior wall portion, and a flexible porous grid disposed between the interior and exterior wall portions. In this regard, means for transporting moisture through the flexible porous grid and out of the exterior wall assembly is provided.
The accompanying drawings are included to provide a further understanding of the present invention and are incorporated in and constitute a part of this specification. The drawings illustrate the embodiments of the present invention and together with the description serve to explain the principles of the invention. Other embodiments of the present invention, and many of the intended advantages of the present invention, will be readily appreciated as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts.
In the following Detailed Description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology, such as “top,” “bottom,” “front,” “back,” “leading,” “trailing,” etc., is used with reference to the orientation of the Figure(s) being described. Because components of embodiments of the present invention can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.
In one embodiment, the first sealed exterior wall assembly 24 is an above-grade exterior wall, and second sealed exterior wall assembly 26 is a below-grade exterior wall. The ventilation assembly 22 is fluidly coupled to the exterior wall assemblies 24, 26, and in one embodiment, includes a head end unit 28, air supply conduits 30, 32, and air return conduits 34, 36, where the conduits 30-36 extend from head end unit 28 into an interior of the sealed exterior wall assemblies 24, 26.
For example, in one embodiment head end unit 28 supplies conditioned dry air through air supply conduits 30, 32 into above-grade exterior wall assembly 24 and below-grade exterior wall assembly 26. Air return conduits 34, 36 remove air, for example relatively humid air, from the sealed above-grade exterior wall assembly 24 and below-grade exterior wall assembly 26, and deliver the return air to head end unit 28. In one embodiment, a humidity sensor 40 is coupled between air return conduit 38 and head end unit 28, although other suitable locations for humidity sensor 40 along a return path from exterior wall assemblies 24, 26 to head end unit 28 are also acceptable.
In one embodiment, desired structural openings, such as a window 50 and a door 52, are formed in the exterior wall assemblies 24, 26 that provide a pathway for the ingress of moisture into structure 20. While it is desirable to have window 50 and door 52 formed in structure 20, such openings provide a potential pathway for the entrance of moisture into the sealed exterior wall assemblies 24, 26.
In one embodiment, air supply conduit 30 is disposed in a zone adjacent to window 50, and air supply conduit 32 is disposed in a zone adjacent to door 52, to supply these potential moisture entry areas with conditioned, dry air. In another embodiment, air supply conduit 30 surrounds window 50, and air supply conduit 32 surrounds door 52. In any regard, air supply conduits 30, 32 supply conditioned, dry air to exterior wall assemblies 24, 26, and air return conduits 34, 36 remove air (at a typically higher humidity) from exterior wall assemblies 24, 26 and deliver the humid air back to head and unit 28 to cyclically condition exterior wall assemblies 24, 26.
Insulation 64 is a thermally insulating filler configured for placement in an exterior wall. In one embodiment, insulation 64 is a fiberglass insulation. In another embodiment, insulation 64 is a blown fibrous insulation. In general, insulation 64 is disposed between studs used to frame exterior wall assembly 24, and can include rolls or sheets of insulating material.
In one embodiment, interior wall portion 60 includes a sheathing board 70 and an air barrier sheeting 72 attached to sheathing board 70. In one embodiment, and is best illustrated in
Sheathing board 70 is generally a structural board suited for construction of new homes and commercial buildings. In one embodiment, sheathing board 70 is an oriented strand board, although other structural boards suited for the construction of walls are also acceptable.
Air barrier sheeting 72 is generally a single layer of polymeric film suited for adhering to sheathing board 70. In one embodiment, air barrier sheeting 72 is a polyethylene film, although other films and construction fabrics suited for covering sheathing board 70 are also acceptable.
In one embodiment, exterior wall portion 62 includes a second sheathing board 80, a water barrier sheeting 82 attached to sheathing board 80, and exterior cladding 84 attached to the water barrier sheeting 82.
Sheathing board 80 is highly similar to sheathing board 70. Water barrier sheeting 82 is attached to an exterior face of sheathing board 80 to provide a level of weather resistance for exterior wall portion 62. In one embodiment, water barrier sheeting 82 is a flash-spun polyethylene nonwoven fabric that is adhered, for example by stapling, to the exterior face of sheathing board 80. Exemplary materials for water barrier sheeting 82 include Tyvek® house wrap, wax coated fabrics, tarpaper and the like, although other suitable materials and/or fabrics are acceptable.
Exterior cladding 84 includes suitable exterior insulation and finish systems (EIFS) such as, for example, stucco finishes, shakes including cedar shakes, vinyl and metal siding, plastic and wood siding, and the other suitable exterior wall coverings.
In one embodiment, flexible grid 66 is disposed within opening 68 and bounded by sheathing board 80 on one side and by insulation 64 on an opposing side. In this manner, flexible grid 66 provides an air passageway between insulation 64 and exterior wall portion 62, and is configured to transport moisture that accumulates within exterior wall assembly 24 along opening 68 and away from insulation 64 and exterior wall portion 62.
In one embodiment, interior wall portion 90 includes a sheathing board 100 and an air barrier sheeting 102 attached to the sheathing board 100. Sheathing board 100 and air barrier sheeting 102 are highly similar to sheathing board 70 and air barrier sheeting 72 described with reference to
In one embodiment, exterior wall portion 92 forms a foundation of structure 20 (shown in
Insulation 94 is highly similar to insulation 64. As illustrated in
In one embodiment, flexible grid 110 is a single layer structure formed of a random distribution of fibers in a matt or fabric-like sheeting. In one exemplary embodiment, flexible grid 110 is a nonwoven sheeting including a fibrous core 116. For example, in one embodiment flexible grid 110 is a nonwoven web of randomly distributed polyolefin fibers where first surface 112 and second surface 114 are thermally treated (e.g., by embossing, or calendering, or by hot can treating) to define a relatively smooth and flat surface.
Generally, core 116 defines a plurality of chambers that form a network, or air space, between first surface 112 and second surface 114. In one embodiment, core 116 defines a “dead” air space. In another embodiment, core 116 defines an air space configured to permit air and moisture transport.
In one embodiment, flexible grid 110 is permeable to moisture vapor and impermeable to liquid water, and includes a surface energy-reducing additive, such as a fluorochemical, added to fibrous core 116. The surface energy-reducing additive is melt-added to the fibers during formation in one embodiment. In another embodiment, the surface energy-reducing additive is added topically to the fibers after formation.
In one embodiment, strands 118 are aligned in a first direction, for example a horizontal orientation, and strands 119 are aligned in a second direction not equal to the first direction, for example, a vertical orientation. In this manner, air channels M1-M5 and N1-N4 are defined in at least two orientations. In one embodiment, the voids formed by the overlapping strands 118/119 provide air passageways extending through core 121, and air channels M1-M5 and N1-N4 provide air passageways that are approximately orthogonal to the air passageways through the core defined by the voids.
In one embodiment, air channels M1-M5 are vertical air channels and air channels N1-N4 are horizontal air channels. In one exemplary embodiment, and with reference to
Film layer 122 is generally a substantially continuous surface and is suitable for contact and/or adhesive attachment to a solid construction surface. In this regard, film layer 122 is in one embodiment a polymeric film that is permeable to moisture vapor and impermeable to liquid water. In another embodiment, film layer 122 is a polymeric film that is mechanically perforated to permit the passage of air, moisture vapor, and water. In another embodiment, film layer 122 is a mesh netting permeable to air, moisture vapor, and bulk moisture.
As described above, film layer 122 is permeable to moisture vapor and impermeable to liquid water, according to one aspect of the present invention. In one embodiment film layer 122 includes a surface energy-reducing additive, such as a fluorochemical, a wax, a silicone, or an oil. In one aspect of the present invention, the surface energy reducing additive (for example, a carbon-8 fluorochemical) is applied as a topical additive to film layer 22; in another embodiment, the surface energy reducing additive is a melt additive added to film layer 122 during processing of film layer 122.
Porous backing 124 is generally configured for contact with insulation 94 (shown in
Reticulated core 126 generally separates film layer 122 and porous backing 124 to form an air passageway configured to fit within opening 68 (shown in
In one embodiment, reticulated core 126 is an expanded polymeric film that is porous to air and liquid. In another embodiment, reticulated core 126 is a felted network of fibers. In general, reticulated core 126 provides a measurable degree of separation between film layer 122 and porous backing 124 to form an air spacing therebetween. In this regard, in one embodiment reticulated core defines a thickness D of between 0.05 inch and 2.0 inches, preferably reticulated core 126 defines a thickness D of between 0.1 inch and 1.0 inch, and more preferably reticulated core 126 defines a thickness D of between 0.25 and 0.75 inch. To this end, a thickness of flexible grid 120 is compatible with insertion of grid 120 into an exterior wall assembly such that the wall assembly will comply with building and construction codes.
In one embodiment, each of the flexible grids 110, 120 is sufficiently flexible to be rolled onto a core and suitable for delivery to a construction site in, for example, roll form. In another embodiment, each of the flexible grids 110, 120 is sufficiently flexible to be folded multiple times and suitable for delivery to a construction site in, for example, a folded sheet form.
Porous backing 124 is secured over another end of reticulated core 126. In one embodiment, film layer 122 and porous backing 124 are thermoplastically sealed to reticulated core 126. In an alternate embodiment, film layer 122 and porous backing 124 are adhesively adhered to reticulated core 126. As illustrated in
In one embodiment, flexible grid 144 is adhesively attached to sheathing board 122. In this manner, exterior wall portion 140 is suitable for use in the construction trades in forming a sealed exterior wall assembly, for example exterior wall assembly 24 (shown in
In one embodiment, reticulated core 150 includes a honeycomb lattice of chambers defined by walls 151 that extend away from sheathing board 142. In a manner analogous to
Flexible grids 110 and 120 provide for a passive transportation of moisture away from interior surfaces of exterior wall assemblies 24, 26. In one embodiment, flexible grids 110 and 120 are disposed in an interior opening, for example opening 68 (shown in
In another embodiment, and as best illustrated in
With this in mind, in one embodiment head end unit 28 is a heating ventilation air conditioning (HVAC) unit including a compressor (not shown) maintained in a compressor side 160, a blower and a blower motor (neither shown) maintained within a blower housing 162, air return ducts 164, and humidity sensors 166 aligned with air return ducts 164.
As illustrated in
In one embodiment, controls 170 are set to a desired set point to maintain a relative humidity level within exterior wall assemblies 24, 26 (shown in
Thereafter, a blower within head end unit 28 continues to remove air from exterior wall assemblies 24, 26 to enable humidity sensor 166 to continue sensing a relative humidity within the exterior wall assemblies 24, 26. In one embodiment, consecutive readings of the relative humidity by the humidity sensor 166 indicating that air extracted from exterior wall assemblies 24, 26 is below the desired humidity set point will activate head end unit 28 to an off position.
In one embodiment, head end unit 28 is programmed to cycle between on and off positions over a set time interval (e.g., every 30 minutes). In another embodiment, head end unit 28 is programmed to cycle between on and off positions based upon a relative humidity reading from within exterior wall assemblies 24, 26 by a separate humidity sensor (not shown) within exterior wall assemblies 24, 26. One aspect of the present invention provides for a continuous operation of head end unit 28 in continuously supplying dry, conditioned air to exterior wall assemblies 24, 26, useful, for example, in drying exterior wall assemblies in tropical climates.
As illustrated in
Structure 182a defines an outside diameter O.D. and an inside diameter I.D. In one embodiment, the O.D. of structure end 182a is between 0.1 inch and 1.0 inch, preferably the O.D. of structure end 182a is between 0.2 inch and 0.5 inch. For example, in one embodiment a 0.25 inch thick flexible grid 120 is secured within exterior wall assembly 24, and a structure end 182a of air supply conduit 30 having a 0.25 inch O.D. is coupled to flexible grid 120. Wall 204 defines a thickness that is suited for supplying air through conduit 30.
Orifices 202 are configured to deliver a flow of air, for example conditioned air from structure end 182a of air supply conduit 30 into an exterior wall assembly, such as exterior wall assembly 24 (shown in
Structure 20 can include a plurality of zones, for example a zone directed to removing moisture from around a window, and a separate second zone for removing moisture from around a door. In another embodiment, an entire exterior wall assembly, for example exterior wall assembly 26, is serviced by a single zone. It is to be understood that structure 20 can include multiple zones within multiple exterior wall assembly structures, all controlled by head end unit 28. Reference is made to
During use, and with additional reference to
With additional reference to
Process 254 queries whether the relative humidity level within a zone of exterior wall assembly 24 is acceptable. If the relative humidity level is acceptable, process 256 provides for sensing a humidity level in a next zone of the exterior wall assembly 24 or of structure 20. In an iterative manner, process 258 provides for sensing a humidity level in a last zone of an exterior wall assembly 24/structure 20 where prior zones of the structure were evaluated to have an acceptable relative humidity level. In the case where each zone of structure 20 has an acceptable relative humidity level, process 260 provides for a timed out wait period prior to cycling system 250.
With additional reference to process 254, in the case where the relative humidity level within a zone of exterior wall assembly 24 is not acceptable, process 262 provides for cycling head end unit 28 to supply conditioned dry air through air supply conduits 30, 32. Thus, head end unit 28 supplies conditioned air to the zone having a relative humidity level that is above the set point, and process 266 provides for sensing the relative humidity of air returning through air return conduits 34, 36 extracted from the too humid zone. A further query is made of the zone in process 254, consistent with one drying cycle of system 250.
In one embodiment, and in particular during periods of relatively dry weather, process 260 signals to head end unit 28 that conditioned air is not called for by any zone. Thus, head end unit 28 does not cycle between the on and off positions, but rather is maintained in an off position, but ready for subsequent cycling.
In addition, and with reference to
In contrast, winter seasons and summer seasons can create a natural humidity gradient across surfaces of structure 20 that results in frequent cycling of head end unit 28. For example, during winter months associated with cold and dry exterior air temperatures and relatively warm interior air temperatures, the large temperature and humidity gradients between the interior air of structure 20 and the environment outside of structure 20 combine to cause moisture vapor in the air to condense upon surfaces of exterior wall assemblies 24, 26. Thus, during winter months, humid air within structure 20 will condense on, for example, sheathing board 70 and air barrier sheeting 72.
This condensation can lead to moisture accumulation along air barrier sheeting 72 and insulation 64. Aspects of the present invention provide for humidity sensors 166 that sense a relative humidity associated with exterior wall assembly 24. When the relative humidity within exterior wall assembly 24 exceeds a desired set point, head end unit 28 is activated to an on condition, supplying condition dry air through air supply conduits 30, 32, and removing moisture from within exterior wall assembly 24 via air return conduits 34, 36. Thus, moisture within exterior wall assembly 24 is driven to opening 68 and transported through flexible grid 66, to be conditioned by head end unit 28.
With the above in mind, in one embodiment head end unit 28 cycles between on and off settings periodically (e.g., every fifteen minutes) to maintain the desired relative humidity within wall assembly 24. In contrast, during relatively dry months, head end unit 28 might not cycle to the on position for periods of greater than one week.
Aspects of the present invention have been described that provide for dynamically venting an exterior wall assembly to remove moisture from inside a sealed and insulated exterior wall. In particular, sealed exterior wall assemblies have been described that can accumulate moisture either through natural condensation processes or through a failure in weather proofing or sealing of, for example, doors and windows in an exterior wall assembly. Embodiments of the present invention provide for dynamically ventilating conditioned air through the flexible grid within the exterior wall assembly to displace humid moisture within the exterior wall assembly with conditioned dry air.
Other aspects of the present invention provide for a flexible grid that provides an air passageway within the exterior wall assembly for the passive removal of moisture. Embodiments of the present invention provide for statically ventilating the exterior wall assembly via the flexible grid to remove humidity from the exterior wall assembly.
A sealed exterior wall assembly that is highly energy efficient and in compliance with local and state housing codes has been described that provides for dynamically, and/or passively (statically), venting moisture from the sealed exterior wall assembly.
In one embodiment, the dynamic, and/or passive, venting of moisture from a sealed exterior wall assembly improves the overall energy efficiency of the wall assembly and its associated structure. The removal of moisture from a wall assembly results in increasing the “R-value,” or insulation value of the wall assembly. Since the wall assembly does not retain the potentially harmful moisture, the insulation performs better, the insulating quality is improved, and moisture that otherwise might conduct heat out of the wall assembly is reduced or eliminated, thus increasing the energy efficiency of the wall assembly. Embodiments of dynamically, and/or passively vented exterior wall assemblies as described above will remain warmer in winter, cooler in summer, and can cost-effectively satisfy even the most stringent building codes.
Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this invention be limited only by the claims and the equivalents thereof.
This Utility patent application is related to commonly assigned and concurrently filed Utility patent application Ser. No. ______, entitled EXTERIOR WALL ASSEMBLY having Attorney Docket Number M420.101.101, and which is herein incorporated by reference.
