Abstract:
A straw bale wall vent box is provided in a wall joinery system comprising a lower member, a substantially planar top member, and a plurality of rebar disposed through the top member and a bottom side of the lower member. The lower member can further include insulation, a drainage floor sloping downwardly from an exterior side, and a trim piece extending from the bottom side towards the plaster screed. In some embodiments the trim piece joins the plaster screed. In those embodiments in which the trim piece joins the plaster screed, both sides of the lower member can each include at least one aperture. Additional embodiments are directed to a straw bale wall vent system comprising a plurality of wall vent boxes placed side by side so that the first and second sides of adjacent vent boxes are substantially in contact.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to the field of straw bale construction and more specifically to a vent that is incorporated into the wall joinery system between the bottom of a straw bale wall and the top of its&#39; foundation to allow condensation from within the wall to be removed. 
     Straw bale construction is a technique for building structures that greatly reduces and in some instances can even eliminate the use of lumber by forming walls out of stacked straw bales. The resurgence of straw bale construction has introduced current knowledge about modern materials and construction analysis to create structures that are especially durable and energy efficient when compared to both traditional lumber and non-lumber built structures. For example, modem straw bale construction features steel rebar that is driven through the straw bales that form the walls in order to provide strength, rather than more traditional materials such as bamboo or lumber. In addition, cables can be wrapped from the foundation to the roof-plate to form an exoskeleton. Modern straw bale construction also takes advantage of computer simulation and other techniques presently adapted to building construction to optimize designs for improved energy efficiency, for example. 
     The greatest strengths of straw bale construction are the fact that it is using a waste product as a building material and that wall structures having insulation values from r50-r60 are possible. These two factors make this construction medium an extremely promising component for addressing the global energy situation. However, there are several places where this technique needs refinements. 
     One involves the most vulnerable point of straw bale construction, namely moisture that tends. to collect in the lower outside corner of the wall. Therefore, the need exists for a vent system incorporated into the wall joinery system between the bales and the foundation in order to increase the longevity of straw bale wall systems. When kept dry, bales have been shown to last in excess of 100 years. 
     Straw bale construction combines well with other building technologies like greenhouses and cob for thermal mass. As a result, structures that combine the advantages of several natural building techniques are facilitated by straw bale—allowing designs of maximum diversity, efficiency, and comfort. 
     These four advantages make straw bale special with respect to the following environmental considerations: 1) Reduced lumber consumption, 2) Increased thermal efficiency, 3) Use of a waste product as a building material, and 4) Adaptability to other building technologies. Clearly, a system that would increase the longevity of straw bale wall systems would further advance these environmental factors. 
     As shown in FIG. 1, straw bale structures typically include a cement foundation  10  and a wall  12  disposed thereon. The wall  12  is built of a plurality of straw bales  14  held in place by a plurality of steel rebar  16 . The rebar  16  between a first row  18  of straw bales  14  and the foundation  10  is set in the foundation  10  while the cement is still wet. Thereafter, the first row  18  of straw bales  14  is set in place such that each bale  14  is impaled onto rebar  16  protruding from the foundation  10 . FIG. 1 includes a partial cut-away section to show several rebar  16  set into the foundation  10  and protruding up into a straw bale  14 . A new set of rebar  16  is then driven into the first row  18  of bales  14  such that approximately half of the length of each rebar  16  protrudes out of the bales  14 . A next row of bales  14  is then impaled on the rebar  16  and the process is repeated. It will be apparent to one skilled in the art that this technique can be varied in many ways including the offset of the bales  14  from one row to the next as well as in terms of the number of rebar  16  used per bale  14 , the particular arrangement of rebar  16 , and how that arrangement is offset between adjacent rows of bales  14 . 
     As shown in FIG. 2 a typical straw bale wall  12  includes both an interior siding  20  and an exterior siding  22 . The interior siding  20  is commonly formed of plaster and is provided to prevent straw and straw dust from contaminating the interior of the structure, to provide a preferred surface for painting and anchoring fixtures, and to improve the insulation value of the wall  12 . The exterior siding  22  is commonly formed of stucco and is provided to prevent the bales  14  from degrading due to sun, rain, and wind, to provide a preferred surface for painting and anchoring fixtures, and to improve the insulation value of the wall  12 . An interfacial layer (not shown) is provided on both sides of the wall  12  to improve the adherence of sidings  20 ,  22 . Interfacial layer  24  is commonly chicken wire. 
     Straw bale walls  12  have proven to be strong and durable, and have excellent insulating properties. However, it has also been found that warm, moist air from within the structure can penetrate the plaster of the interior siding  20 . This can cause condensation  23  to form on an interior surface  24  of the exterior siding  22 . The condensation  23  then tends to drip down the interior surface  24  and pool at the bottom along the foundation  10 , as shown in FIG. 2, and can cause the straw to rot. 
     Accordingly, what is desired is a venting system that can be interposed between the wall  12  and the foundation  10  to collect moisture and to vent it back into the interior of the structure without significantly increasing building costs and without significantly diminishing the insulation value of the wall  12 . 
     SUMMARY OF THE INVENTION 
     According to an embodiment of the present invention, a straw bale wall vent box comprises a lower member, a substantially planar top member, and a plurality of rebar disposed through the top member and the bottom side of the lower member. The lower member includes substantially parallel first and second sides, an exterior side, and an optional bottom side. The top member is substantially planar and includes a plurality of apertures, and can further include a stucco screed on an exterior end and a plaster screed on an interior end. The top member is disposed above and substantially parallel to the bottom side of the lower member, and is joined to a top edge of the exterior side of the lower member. The plurality of rebar is disposed through the top member and the bottom side of the lower member. This structure is advantageous as the apertures allow moisture from the straw bales to enter the vent box from which it can then vent into the air space above the foundation. The rebar serves to transfer the load from the top member to the foundation. 
     It will be appreciated that although the embodiments described herein and shown in the drawings all include stucco and plaster screeds, these are not critical elements to the invention and in some simple embodiments they are excluded. One of skill in the art will readily see how the invention can be constructed and used without screeds, or with only an exterior or interior screed. 
     The lower member can further include a drainage floor sloping downwardly from the exterior side, the rebar being disposed through the drainage floor. In those embodiments that include a drainage floor the bottom side is optional. The lower member can also include a trim piece substantially parallel to the exterior side and extending from the bottom side towards the plaster screed. The trim piece in some embodiments joins the plaster screed. In some embodiments the drainage floor joins the trim piece along its top edge, and in other embodiments along a line beneath and substantially parallel to the top edge. The drainage floor is advantageous to guide moisture towards the interior side of the vent box. In those embodiments in which the drainage floor joins the trim piece along its top edge, moisture can drain out of the vent box. In those embodiments in which the drainage floor joins the trim piece beneath the top edge, the moisture will tend to evaporate and vent out of the box through the opening between the top edge of the trim piece and the plaster screed. 
     In those embodiments in which the trim piece joins the plaster screed, the first and second sides of the lower member each can include at least one aperture. In those embodiments that include a drainage floor, the apertures in the first and second sides are disposed above the line along which the drainage floor joins the two sides. In other embodiments in which the trim piece joins the plaster screed, the first and second sides of the lower member are each bounded by the bottom side, the exterior side, and the drainage floor. In each of these embodiments the advantage of either apertures or first and second sides that do not extend beyond the drainage floor is to provide for air circulation between adjoining vent boxes when configured as a straw bale wall vent system as will be described in greater detail below. 
     Some embodiments include insulation within the bottom portion of the lower member. The insulation is advantageous to insulate against the cold of the foundation. In some of these embodiments a space within the lower member is defined by the bottom side, the drainage floor, the exterior side, and the first and second sides, and this space includes an insulation. However, in those embodiments that do not include a drainage floor the insulation can simply form a layer on the bottom side of the lower member. 
     Additional embodiments of the present invention are directed to a straw bale wall vent system comprising a plurality of wall vent boxes, as previously described, wherein the plurality of wall vent boxes are placed side by side so that the first and second sides of adjacent vent boxes are substantially in contact. In those embodiments in which each vent box includes a trim piece that extends upwardly to join the plaster screed, the plurality of adjoining vent boxes essentially forms a tube. Therefore, to provide air circulation necessary to remove excess moisture, the system further includes an air blower configured to force air into one of the vent boxes, and an outlet in one of the vent boxes through which the air may escape. 
     These and other advantages of the present invention will become apparent to those skilled in the art upon a reading of the following descriptions of the invention and a study of the several figures of the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be readily understood by the following detailed description in conjunction with the accompanying drawings, with like reference numerals designating like elements. 
     FIG. 1 is a perspective view of a straw bale wall constructed according to the prior art; 
     FIG. 2 is a cross-sectional view of a straw bale wall constructed according to the prior art; 
     FIG. 3 is a cross-sectional view of an embodiment of a straw bale wall vent box of the present invention disposed between a straw bale wall and a foundation; 
     FIG. 4 is a perspective view of an embodiment of a straw bale wall vent box of the present invention; 
     FIG. 5 is a cross-sectional view of another embodiment of a straw bale wall vent box of the present invention disposed between a straw bale wall and a foundation; 
     FIGS. 6 is a perspective view of another embodiment of a straw bale wall vent box of the present invention; 
     FIG. 7 is an cross-sectional view of yet another embodiment of a straw bale wall vent box of the present invention; 
     FIG. 8 is a perspective view of yet another embodiment of a straw bale wall vent box of the present invention; and 
     FIG. 9 is a perspective view of an embodiment of a straw bale wall vent box system of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1 and 2 were discussed with respect to the prior art. 
     FIG. 3 shows a cross-section of a straw bale wall vent box  30  of the present invention disposed between a foundation  10  and wall  12 , and FIG. 4 shows a perspective view of the same vent box  30 . Vent box  30  comprises a lower member  32  having substantially parallel first and second sides  34 ,  36 , an exterior side  38 , and a bottom side  39 . Vent box  30  further includes a top member  40  including a plurality of apertures  42 . The top member  40  is disposed above and substantially parallel to the bottom side  39  and includes a stucco screed  44  on an exterior end and a plaster screed  46  on an interior end. The top member  40  joins a top edge  47  of the exterior side  38  of the lower member  32  proximate to the exterior end of top member  40 . In this particular embodiment top member  40  additionally joins top edges  48 ,  49  of sides  34 ,  36 , as shown. It should be noted that as used herein, a plurality of apertures  42  is meant to be interpreted broadly to include any type of passageway for moisture. Accordingly, top member  40  can include, for example, a moisture permeable material and a plurality of apertures  42  would be the channels through the material that allow the moisture through. 
     Additionally, vent box  30  also includes a plurality of rebar  16  disposed through the bottom side  39  of the lower member  32  and through the top member  40 . Each of the sides of the vent box  30  are constructed out of durable construction materials such as sheet aluminum. It will be appreciated by those skilled in the art that a vent box  30  of the present invention can be fabricated in numerous ways, depending on the choice of materials. Of particular importance, however, is that rebar  16  should be securely joined to top member  40  and bottom side  39 , for example by welding or brazing, so that the loads on these surfaces is transferred to the rebar  16 . 
     FIG. 5 shows in cross-section a another embodiment of a straw bale wall vent box  50  of the present invention disposed between a foundation  10  and wall  12 , and FIG. 6 shows a perspective view of the same vent box  50 . Vent box  50  comprises a lower member  52  having substantially parallel first and second sides  34 ,  36 , an exterior side  38 , a drainage floor  53 , and an optional bottom side  39 . Vent box  50  can also include a trim piece  54  that extends upwardly towards a plaster screed  46  from an interior edge  55  of the lower member  52 . In some embodiments, as shown in FIG. 6, trim piece  54  joins drainage floor  53  along a lower edge  56  of drainage floor  53 . In other embodiments the trim piece extends upwardly beyond lower edge  56  towards plaster screed  46  to form a narrow gap between the top of the trim piece  54  and the bottom of the lip of the plaster screen  46 , as seen in FIG.  5 . In some embodiments first and second sides  34 ,  36  can also include one or more apertures  57  disposed above the lines where the drainage floor  53  joins each of the sides  34 ,  36 . In those embodiments where the trim piece  54  joins plaster screed  46 , as shown in FIG. 7, one or more apertures  57  are necessary to allow ventilation between adjacent vent boxes  70 , as will be described below with reference to a straw bale wall vent system. 
     Vent box  50  further includes a top member  40  including a plurality of apertures  42 . The top member  40  is disposed above and substantially parallel to the bottom side  39  and includes a stucco screed  44  on an exterior end and a plaster screed  46  on an interior end. The top member  40  joins a top edge  47  of the exterior side  38  of the lower member  52  proximate to the exterior end of top member  40 . In this particular embodiment top member  40  additionally joins top edges  48 ,  49  of sides  34 ,  36 , as shown. Additionally, vent box  50  also includes a plurality of rebar  16  disposed through the drainage floor  53  and the bottom side  39  of the lower member  52  and through the top member  40 . As above, each of the sides of the vent box  50  are constructed out of durable construction materials, and the rebar  16  should be securely joined to top member  40  and drainage floor  53 , and bottom side  39  where present. 
     In some embodiments of vent box  50  a space  58  within lower member  52  defined by the drainage floor  53  and the three sides  34 ,  36 , and  38  is filled with an insulation  60 . In those embodiments that include a bottom side  39 , side  39  also will define the space  58  within lower member  52 , and in those embodiments that do not include bottom side  39  the insulation  60  preferably should not extend below where bottom side  39  would be. The insulation  60  can be either a solid material such as foamed polyurathane or sections of fiberglass, or can be a loose material such as packing peanuts. Inclusion of a bottom side  39  can be advantageous to hold the insulation  60  in place through assembly of the vent box  50  and through subsequent acts of storage, shipment, handling, and installation. 
     FIG. 8 shows a perspective view of another embodiment of a straw bale wall vent box  80  of the present invention. Vent box  80  differs from the previously described embodiments only in that first and second sides  82 ,  84  do not join top member  40 . Rather, each of the two sides  82 ,  84  have a top edge  86 ,  88  that joins the drainage floor  53 . Thus, the top member  40  only contacts the bottom member  90  along top edge  47  of the exterior side  38 . It will be apparent that this embodiment would also allow ventilation between adjacent vent boxes  80  as part of a straw bale wall vent system, much as vent box  70  shown in FIG.  7 . The embodiment shown in FIG. 8 can also be modified such that edge  56  is coincident with edge  55 , and so that drainage floor  53  joins exterior side  38  and top surface  40  along top edge  47 . 
     FIG. 9 shows a perspective view of an embodiment of a straw bale wall vent system  100  of the present invention. Multiple vent boxes  30 ,  50 ,  70 ,  80  can be assembled end to end as shown to create a wall vent system  100 . Vent boxes  70 ,  80  are particularly desirable as they allow ventilation to occur between adjoining members. In this way a vent box system  100  can run continuously around an entire foundation and form a closed loop, with specially adapted pieces for comers and the like. In those embodiments of the system  100  that include vent boxes  70 ,  80 , the system can further include a first inlet  105  and a second inlet  110 . In some embodiments, such as the one shown in FIG. 9, air is drawn into the system  100  through first inlet  105  and exits through second inlet  110 . The air can be drawn through the system by any vacuum source, for example, a vacuum pump. A particularly convenient vacuum source in the home, however, is a fireplace  115 . As is well known, rising air in a chimney of a fireplace  115  draws air in behind it because it is creating a partial vacuum. Accordingly, in some embodiments second inlet  110  is configured to vent into a fireplace  115 . 
     It should be noted that although FIG. 9 shows second inlet  110  configured in much the same location as an aperture  57  would be located, either inlet  105 ,  110  can be located on any of the walls of the vent box that is convenient. In other embodiments air is forced into the system  100  through first inlet  105  and exits through second inlet  110 . The air can be forced into the system by any forced air source, for example, a source of compressed air, a fan, or a blower. It should also be noted that although the vent box system is herein described in terms of an assembly of a plurality of vent boxes, it will be appreciated by those of skill in the art that the same effect can be achieved by suitable modification of regular commercial air ducts. Such modification would include, for example, running rebar through the duct so that the duct can support the straw bale wall over the foundation. 
     FIG. 9 shows an additional feature that can be useful in the assembly of a wall vent system  100 . Vent boxes  30 ,  50 ,  70 ,  80  can be configured to include a slot  120  and tab  125  that interlock when multiple vent boxes are placed together to form a vent system  100 . It will be appreciated that in addition to placing a slot  120  and tab  125  on the top member  40  as shown, a slot  120  and tab  125  could also be placed on any of the components of the bottom member. It will further be appreciated that multiple slots  120  and tabs  125  can be employed per vent box. 
     Although the foregoing invention has been described in some detail for the purpose of clarity of understanding, it will be apparent that certain changes and modifications may be practiced within the scope of the appended claims. Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.