Patent Application
20110252723
Related fields include roofing material for construction; particularly roofing that includes flexible material and reflective “cool” roofing.
Roofing, an essential element of any type of shelter, presents excellent opportunities for energy conservation in climate-controlled structures. Where the inside of the structure needs to be kept warmer than its surroundings, the roof can be designed to trap internal heat and absorb incident sunlight to convert to heat. Where the inside of the structure needs to be kept cooler than its surroundings, the roof can be designed to dissipate internal heat and reflect incident sunlight.
Roofing also presents opportunities to reduce the impact of an increasing human population on the natural environment. Use of recycled materials reduces landfill content. Reducing the use of lumber reduces the need for timber harvesting. Reducing the use of lumber may also may reduce the risk of spreading fire among densely packed residences, since wood is naturally flammable and building lumber is often untreated for flame retardance. Eliminating or carefully isolating toxic content keeps toxics out of the local soil and water. Roofing with a longer useful life reduces the demand for replacement. According to a 2008 Lawrence Laboratories study published in the Climate Change journal, every 1,000 square feet of solar-reflective roofing can offset 10 tons of carbon-dioxide emission. Energy-saving building design can also reduce greenhouse emissions from the power plants that would otherwise operate at higher capacity to fuel internal climate control.
Besides reducing the burden on the environment, roofing presents opportunities to reduce the total cost of new construction. If construction materials and/or labor can be made less costly, buildings become affordable to a wider range of would-be homeowners and entrepreneurs, improving the local economy, standard of living, and social stability.
Typical conventional roofing is fairly complex to install, although the materials and processes are well known.
Various approaches have been taken to make roofing reflect more solar radiation. So far, the most widely commercialized are light-colored paints or foams. Paints are typically low-cost, though the advertised reflectivity figures of 70-80% may not apply across the entire solar spectrum, particularly under typical dusty outdoor conditions. Foams can also help insulate the roof, but are often fragile and relatively short-lived (needing re-spraying in 5 years, compared to the 9-15 year life of typical conventional roofing. Also, some foams and paints may contain toxic chemicals, requiring extra precautions to keep them contained during installation. Some existing “cool roofs” based on a white or light-colored paint or foam coating lose their solar reflectivity as atmospheric dust builds up, but are too delicate for vigorous or frequent cleaning. Such roofs may also be damaged if stepped on, as for cleaning a chimney or dryer vent, or adjusting an aerial antenna or satellite dish.
Likewise, roofing made of various recycled materials has been developed. Typically, the materials recycled are other construction materials such as asphalt, bitumen, concrete and fiberglass. While this is beneficial, these materials may not be readily available in new or expanding communities unless demolition on a similar scale has recently happened nearby. Their weight also adds to the expense of transportation to and from the recycling site. It would be more desirable to recycle a problem material that is discarded more continuously and is easier to transport. Lighter weight would also decrease the demands on the strength of the underlying structure, potentially enabling the use of less material or less-expensive material.
Both reflective roofing and roofing that incorporates recycled material have also encountered acceptance barriers based on esthetics. Apparently, although conserving energy and protecting the environment are popular high-profile goals, strict standards of traditional appearance trump them both in neighborhood-association decisions.
In light of all the above factors, a more integrated type of roofing that is simpler to install and uses recycled plastics would help conserve energy, protect the environment, and make construction and structure ownership more widely affordable. Leeway for customization of its appearance to meet local community standards would increase its chances of acceptance, thus increasing its economic value.
This integrated roofing features reflective, moisture-blocking, insulating, and esthetic layers fabricated into a single sheet or panel. Installation is highly simplified by replacing the usual multiple disparate layers with a single integrated layer that may also be larger in area than conventional roofing components. Reflective features prevent excess solar absorption. A fumed outer surface with heat-release perforations helps the roofing dissipate heat from radiation that is absorbed, or excess heat absorbed from other sources. Some of the layers can be fabricated from recycled plastics.
The sheets or panels can be designed to be joined and trimmed in various ways during installation. Compatible ancillary fittings such as ridge caps and pipe sealers can be made for this roofing. For applications where large numbers of identical or similar structures will be made (housing developments, business parks, mobile homes, monitoring stations), whole roofs (or subsections sized for transport by truck or rail) can be manufactured, tested at the factory, then simply hauled into place with cranes or winches and anchored at the site.
a is an exploded view of one type of pipe sealer compatible with the integrated roofing.
b is a magnified cross-section of an assembled pipe sealer showing one possible mating feature design.
This description will discuss (1) the structure of the integrated roofing, (2) possible fabrication methods, (3) compatible accessory parts, (4) installation options, and (5) specific benefits of its use.
A number of approaches can be taken to customize the color of this integrated roofing to fit the esthetic needs of architects or neighborhood associations, and render that color durable under prolonged weathering and occasional cleaning. The outer layer 208 can be a clear polymer, transparent across the entire visible spectrum, and the color can be that of reflective layer 207a, 207b, or a combination if 207a is partly translucent. Outer layer 208 can alternatively be a transparent color (for example, the red of Spanish tile) and still allow most sunlight to pass through to be reflected by reflective layers 207a and 207b. Color in outer layer 208 may also be applied as distributed dots, stripes, or other shapes separated by transparent interstices. Sunlight passing through the interstices is reflected by reflective layers 207a and 207b. However, an observer looking up at an angle from some distance away (the sidewalk, street, or neighbor's yard) would see a solid-colored roof, similar to the way an array of half-tone dots in a newspaper photo can appear as a solid shade of gray. If the color is mixed or laminated into reflective layer 207a, reflective layer 207b, or outer layer 208, it will be impervious to pressure-washing and other low-cost methods of cleaning, and it will stand up to any foot traffic necessary for maintenance, repair, or seasonal decoration An ultraviolet-blocking additive may optionally be added to outer layer 208 to relax the need for inner layers to resist UV degradation and allow a wider variety of recycled plastics to be used in those layers.
Moreover, if the roof beams will be exposed inside the structure rather than covered with a dropped ceiling or the like, underlayer 201 can also be esthetically colored or textured.
A number of manufacturing options are feasible. The best choice will depend on the exact nature of the polymers and any other materials, and those with experience in manufacturing with those materials will be able to knowledgeably choose among the candidate methods. Underlayer 201, made of plastic, fiberglass, or both, can initially be formed by molding, webbing, or other suitable methods. If insulation 202 is loose (e.g., pellets of recycled Styrofoam™ or similar material), then a honeycomb or other cell-based support array 203 can be molded as part of, or initially adhered to, underlayer 201; insulation 202 can be poured into the cells and any overfill skimmed off; and vapor barrier 204 can be adhered onto the tops of the cell walls, closing the cells and sealing the loose insulation inside. If insulation 202 is a deformable mat such as recycled spun fiberglass with or without included pellets of foam or fragments of polymer, support array 203 may take the form of standoffs to prevent deformation of the integrated roofing. These standoffs can be made as part of underlayer 201, insulation layer 202, or vapor barrier layer 204. If insulation 202 is expected to hold its shape easily for decades under the expected static and dynamic loading (for example, recycled bottle plastic with air bubbles or foam pellets inserted in the melt), then supports 203 may not be needed. Outer layer 208 may be molded or vacuum-formed to provide the desired outer texture. Reflective layers 207a and 207b may be similarly formed, or may be applied as liquids on the lower surface of outer layer 208 and the upper surface of vapor barrier 204. If both reflective layers are applied as liquids, air-gap supports 206 could be formed onto, or adhered to, vapor barrier 204 or outer layer 208 and protrude beyond the liquid-coated surface. Layers or sets of layers can be reheated and adhered together by localized surface melting, or cemented together, in either a continuous process or a batch process. Straps or tabs for attaching the roofing element to the underlying structure's beams may be attached to underlayer 201 by a suitable method at a suitable stage in the manufacturing process.
In other embodiments, the mating features can be identical on all four edges to minimize the need for maneuvering panels into a particular orientation. A solid mating strip, which may also be fabricated from recycled plastic, can be used in some designs to help exclude and/or channel moisture.
Various compatible fittings can be made to finish off the roof and accommodate roof-mounted features.
Some roofs change pitch in places other than the peak ridge, for example over dormers or verandas.
Other fittings, such as edge caps or gutter interfaces, can be constructed similarly to the edge caps and angle adaptors.
Pipes extending through roofs must often be accommodated.
b is a magnified cross-section of an assembled pipe sealer showing one possible mating feature design. The part numbers in
An alternate mating feature design enables a flexible flange with a diameter about the same as that of the rigid flange, saving space where other roof features are close to the pipe. This type of flexible flange would have one or more bottom ridges that press-fit down into corresponding channels in the rigid flange. Weatherstripping or an equivalent extra seal can be added if needed.
Besides being installed directly over the beams of a new structure as has been described, this integrated roofing can also be installed over a worn-out or damaged traditional roof without needing to strip and dispose of all the existing materials. Also, as briefly mentioned earlier, a complete roof (or the largest subsections that can be easily transported) can be pre-fabricated with no seams or with factory-sealed seams. Installation then consists of merely winching the roof into place and anchoring it, and the opportunities for leak formation are minimized. This approach can be low-cost if economy of scale is available, as with planned developments or movable structures where a single design will fit a large number of constructed units.
Because this integrated roofing is both reflective and durable, it can enhance the efficiency of solar panels positioned to receive either direct sunlight or sunlight reflected from the roof.
One advantageous combination is a reflective roof with a partially transparent thin-film solar panel. Thin-film-based solar panels are less expensive and make better use of diffuse sunlight than wafer-based panels, but they are not as efficient because not all the sunlight is absorbed on a single pass through the film. This is mainly because the film is so thin; the absorption spectrum of the material would convert more light to electricity if the light could travel a longer distance through the material. If the solar panel is at least partially transparent, for example if both the front and back electrodes are fabricated from a transparent material such as a tin oxide or zinc oxide, unabsorbed light passing through the back of the solar panel bounces back off the reflective roof surface and into the panel again, where more of it can be absorbed and converted to useful electricity.
“Back-to-back” mounting of solar panels is another way to leverage the roof reflectivity into more solar power from a smaller area. In the example of FIG, 11, a back-to-back pair of panels 1102 and 1105 is mounted at a pitch angle shallower than that of the reflective roof 1110, by using standoff 1112. This enables the use of the more common opaque-backed panels. Top panel 1102 picks up the direct light 1103 from sun 1111; some of this light is reflected as ray 1104 and some is converted. Bottom panel 1105 picks up the light 1113 reflected from roof 1110. This configuration allows top panel 1102 to be a different type of panel from bottom panel 1105. For example, if roof 1110 is a diffuse reflector (acting more like a movie screen than a mirror), top panel 1102 could be a crystalline photovoltaic panel that is very efficient at converting direct light, while bottom panel 1105 could be a thin-film panel that captures diffuse light more effectively. One or both of the panels might even be solar-thermal, with the heat-exchange pipes being sandwiched between panels 1102 and 1105.
Besides being economical to manufacture, unburdening the environment by incorporating recycled plastics, offsetting greenhouse gas effects by reflecting sunlight, installing quickly and inexpensively, and being adaptable to local community architectural tastes, this integrated roofing has a potentially longer useful life than many traditional roofs. The same very slow rate of decomposition that makes plastics so burdensome in landfills is an advantage in structural components. Plastic is not subject to rot and will not support the growth of toxic mold as wood does. Every year that the roof remains functional prevents the material and energy expenditure of replacing it, as well as the environmental impact of disposing of it. The built-in interlocking features allow individual sheets or panels to be replaced in the field if they are damaged, without needing to replace the entire roof If the owner wishes to change the look, a new top layer can be applied to the existing sheets or panels. Furthermore, part or all of this roofing can be recycled again when it does finally reach its end-of-life.
Those skilled in the art will recognize that many variations of this integrated roofing are possible by minor variations on the descriptions and drawings presented here. Therefore, the reader should note that only the claims, rather than any other part of this document, limit the scope of the invention.
