Claims
- 1. A thermally efficient, protected membrane roofing system for insulating the interior of a building from ambient thermal cycling and for insuring water impermeable integrity of the building, said roofing system comprising:
- a water impermeable membrane overlaying a roof deck or the like;
- an array of factory assembled roofing panels positioned in a juxtaposed position across the roof deck and operably and overlaying said water impermeable membrane, said panels each including at least,
- a vapor barrier course, and
- an insulation course overlaying the vapor barrier course, said insulation course serving to protect and isolate the water impermeable membrane from external thermal cycling and said vapor barrier course serving to protect the insulation course from outwardly driven water vapor from the building or the surface of the water impermeable membrane;
- a waterproof, but vapor permeable, tape bonded to the exterior surface of adjacent roofing, insulation panels to isolate the seam from penetration of surface water while concomitantly permitting the escape of water vapor from beneath the panels to the atmosphere through the peripheral seams of said roofing insulation panels, said waterproof tape including
- a plurality of conical extensions aligned along the edges of said tape for physical penetration into the outer surface of adjacent roofing panels; and
- a protective and retaining course overlaying the outer surface of the roofing panels to isolate the panels from ultraviolet degradation and retaining the panels in position upon the roofing deck.
- 2. A thermally efficient, protected membrane roofing system as defined in claim 1 and further comprising:
- a course of adhesive overlaying the surface of said strip of waterproof tape having the plurality of conical extension, for binding the strip to the outer surface of the edges of the insulation course.
- 3. A thermally efficient roofing system as defined in claim 1 wherein:
- the roof portion of the building is provided with one or more drains and the upper surface of said insulation course of the roofing panels uniformly slope toward said one or more drains.
- 4. A thermally efficient, protected membrane roofing system for insulating the interior of a building from ambient thermal cycling and for insuring water impermeable integrity of the building, said roofing system comprising:
- a water impermeable membrane overlaying a roof deck or the like;
- an array of factory assembled roofing panels positioned in a juxtaposed position across the roof deck, and operably overlaying said water impermeable membrane, said panels each including at least,
- a vapor barrier course, and
- an insulation course overlaying the vapor barrier course, said insulation course serving to protect and isolate the water impermeable membrane from external thermal cycling and said vapor barrier course serving to protect the insulation course from outwardly driven water vapor from the building or the surface of the water impermeable membrane;
- a waterproof, but vapor permeable, tape bonded to the exterior surface of adjacent roofing, insulation panels to isolate the seam from penetration of surface water while concomitantly permitting the escape of water vapor from beneath the panels to the atmosphere through the peripheral seams of said roofing insulation panels, said waterproof tape comprising
- a plurality of conical extensions aligned along the edges of said taps for physical penetration into the outer surface of adjacent roofing panels;
- the roof portion of the building is provided with one or more drains and the upper surface of said insulation course of the roofing panels uniformly slope toward said one or more drains; and
- a protective and retaining course overlaying the outer surface of the roofing panels to isolate the panels from ultraviolet degradation and retaining the panels in position upon the roofing deck.
- 5. A thermally efficient, protected membrane roofing system as defined in claim 4 and further comprising:
- a course of adhesive overlaying the surface of said strip having the plurality of conical extensions for binding the strip to the outer surface of the edges of the insulation course; and
- a fabric course overlaying the opposite surface of said strip.
- 6. A thermally efficient, protected membrane roofing system for insulating the interior of a building from ambient thermal cycling and for insuring water impermeable integrity of the building, said roofing system comprising:
- a water impermeable membrane overlaying a roof deck or the like;
- an array of factory assembled roofing panels positioned in a juxtaposed position across the roof deck and operally overlaying said water impermeable membrane, said panels each including at least,
- an insulation course, said insulation course serving to protect and isolate the water impermeable membrane from external thermal cycling;
- a vapor barrier course coextensive with said insulation course, said vapor barrier course serving to protect the insulation course from outwardly driven water vapor from the building; and
- an insulating drainage course bonded to said vapor barrier course and being operable to be placed against the water impermeable membrane, said insulating and drainage course comprising a course of generally homogeneous association of expanded polystyrene members coated with an outer film of latex bituminous emulsion wherein the coated polystyrene members are resistant to the penetration of water interiorly within the polystyrene members and concomitantly the latex bituminous emulsion being a waterproof adhesive such that the coated polystyrene members are bonded together at points of contact with random voids created throughout the association to render it both insulating and substantially porous to the passage of water;
- a waterproof, but vapor permeable, tape bonded to the exterior surface of adjacent roofing, insulation panels to isolate the seam from penetration of surface water while concomitantly permitting the escape of water vapor from beneath the panels to the atmosphere through the peripheral seams of said roofing insulation panels; and
- a protective and retaining course overlaying the outer surface of the roofing panels to isolate the panels from ultraviolet degradation and retaining the panels in position upon the roof deck.
RELATED APPLICATION
This application is related to the subject matter of applicant's prior application U.S. Pat. No. 3,971,184 entitled "Insulated Water Impermeable Roofing System" and to the subject matter of applicant's prior U.S. Pat. No. 4,551,494 entitled "Insulation Panel For A Roofing System Or the Like."
This invention relates to an improved thermally efficient protected membrane roofing system or the like for commerical buildings, deck structures and similar structures. More particularly, this invention relates to a protected membrane roofing system for insulating the interior of a building from ambient thermal cycling and for insuring water impermeable integrity of the roofing membrane.
The basic concept of a roof is to act in cooperation with wall surfaces to form an enclosed space which may be isolated from an ambient environment and thus may be temperature and humidity regulated in accordance with intended utilization.
A threshold or common denominator of almost all controlled environments is to maintain the enclosure in essentially a water tight or dry condition. Accordingly over the years the roofing industry has attempted to maintain a water tight or water impermeable roof condition by building a water impermeable barrier, in situ, upon a roof substructure or deck. Such a water barrier has typically assumed the configuration of a laminar composite comprising a plurality of bituminous felt layers with intercalated courses of mopped on bituminous composition.
In many previously known installations, bituminous compound arrives at a job site in solid cylinders. The cylinders are melted in a heater and the hot liquid is then carried in buckets to a roof deck where it is mopped onto a previously prepared roof substructure. A roll of bituminous impregnated felt paper is then carried to the roof and unrolled upon the hot bituminous compound which binds the felt to the roof deck. Three or more courses are then built up over the entire roof structure. The job is finished with a layer of topping gravel. The gravel weights down the felt courses and also serves as a shield to minimize ultra-violet degradation of the felt and bituminous membranes.
Although water impermeable roofing membranes, as previously noted, have been widely utilized in the roofing industry substantial disadvantages have been occasioned. In this connection, elevated roof temperatures may vaporize volatile components in the bituminous compound. The compound then tends to harden and crack in a checkered or "allegator" array. Moreover as the bituminous compound becomes hot during the summer months the overlay course of gravel tends to sink into the membrane. Further, prior roofing systems often developed vapor blisters, splitting or ridging. Similar problems of accelerated aging occur with elasto-plastic membranes where the roofing membrane is placed on top of insulation.
The above factors each tended to create water seepage difficulties which ultimately rendered the waterproofing system unsuitable for its intended purpose.
In addition to water impermeability considerations environmental control criteria dictates internal isolation from thermal cycling which takes place at the exterior surface of a roof. More particularly the exterior surface of a roof may experience temperatures during midsummer as high as 180.degree. Fahrenheit while a winter cold front may drop the temperature as as low as 20.degree. or 30.degree. below zero. The interior surface of the roof, however, should optimally be maintained at a desired interior temperature which typically is 65.degree. to 75.degree. Fahrenheit.
In order to provide thermal protection, an initial practice entailed lining the interior surface of the roof with an insulation composition such as sprayed or layered glass fibers, fiberboard, plastic foams and the like. While such insulation techniques operably reduced thermal cycling problems it severely accentuated the previously outlined difficulties occurring with the felt and bituminous water barrier by isolating the barrier from a relatively stable interior temperature of the building structure. Accordingly, in the past it was not uncommon for roof membranes to require considerable attention and short term replacement.
A significant advance was made in the roofing industry when it was determined that an insulation course could be installed exteriorly on top of the felt and bituminous water barrier. The exterior insulation provided a building with isolation from thermal gradients and concomitantly physically protected the felt and bituminous waterproofing barrier from environmental and physical abuse.
In the above connection, an insulated roof membrane assembly which has attained at least a degree of industry recognition comprise a water barrier of felt and bituminous lamination which is built up, in situ, in a manner as previously discussed. A hot course of bituminous compound is then mopped upon the final layer of felt and generally rectangular panels of polystyrene are laid over the membrane. The polystyrene insulating members are loosely abutted adjacent each other to permit a peripheral drainage channel and a heavy course of aggregate is applied directly upon the upper surface of the thermal insulating members to hold the members in place and isolate the insulation surface from ultra-violet degradation.
Although the above and similar systems have achieved a wide degree of industry utilization, room for significant improvement remains. In this regard, little attention has been directed in the past, to the combination effects of three interrelated factors: (1) external standing water, (2) external moisture, and (3) internal moisture vapor driven from the interior of a building outward. These three factors must be concomitantly addressed and accommodated in order to achieve a thermally efficient roof.
Previously known systems, have been designed to specifically channel water from rain or melting snow from the top surface of the insulation down to the roofing membrane where the water travels across the membrane to roof drains. These prior systems promote the passage of water freely either thru the insulation or thru the joints in the insulation onto the roofing membrane. As a result of such prior construction, buildings covered with these roofing systems loose a significant amount of heat energy in the winter as the water travels over the membrane surface to the roof drains. It is believed that at least a 12% increase in insulation thickness would be required to offset such energy loss in Sweden. The loss of thermal efficiency could be even greater in colder climates.
In addition to thermal inefficiency occasioned in prior insulated roof membrane assemblies, which permit rain water to seep downwardly around lines of panel abutment, water may migrate beneath panels and lift or float the roofing system. In order to obviate this tendency of the insulation to float, a substantial amount of gravel needs to be applied directly to the insulation course in order to maintain it in place. In this connection gravel may be deposited at a rate of 1,000 pounds or more per 100 square feet. The roof deck must therefore be designed to support a considerable amount of weight.
Additionally, rain water which collects in insulation fissures and beneath the insulation panels in prior systems can, over time, permeate and degrade the insulation.
In at least one prior instance it has been invisioned that, in order to reduce the amount of water that is permitted to accumulate between an insulation board and a waterproof roofing membrane, a drainage board of polystyrene beads is positioned beneath an insulation layer. The drainage board is composed of polystyrene beads which have been expanded within a steam mold and self adhered in a loose array at points of contact. This drainage board permits water penetrating the peripheral zone of the insulation course to be drained off of the roof. However, this drainage layer itself is subject to moisture saturation and degradation over time.
In addition to external standing water and moisture, another significant factor in a thermally efficient roofing system, as mentioned above, is moisture vapor driven from the interior of a building outward. More specifically, moisture vapor emanating, from the interior of a building, tends to permate an overlaying insulation layer during a cold cycle when moisture vapor drives are outward.
In the prior art this problem of moisture vapor and its long term adverse effect on an insulation course in a protected membrane roofing system has not been addressed.
The problems suggested in the preceeding are not intended to be exhaustive, but rather are among many which may tend to reduce the effectiveness of prior insulated roofing membrane systems. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that protected membrane roofing systems appearing in the past will admit to worthwhile improvement.
It is therefore a general object of the invention to provide a thermally efficient, protected membrane roofing system or the like which will obviate or minimize problems of the type previously described.
It is another object of the invention to provide a thermally efficient, protected membrane roofing system or the like which will be resistant to the accumulation of external standing water even on a generally flat roofing deck.
It is yet another object of the invention to provide a thermally efficient, protected membrane roofing system or the like wherein a tendency of the insulation to be lifted from underlying water is minimized.
It is still another object of the invention to provide a thermally efficient, protected membrane roofing system wherein insulation properties of the system are maintained even after long term weather exposure.
It is another object of the invention to provide a thermally efficient, protected membrane roofing system wherein removal of external water and moisture is facilitated from beneath the insulation panel.
It is a further object of the invention to provide a thermally efficient, protected membrane roofing system or the like wherein the insulating characteristics of an insulation panel are enhanced and prolonged.
It is a related object of the invention to provide a thermally efficient, protected membrane roofing system or the like wherein a tendency for the migration of water vapor into the insulation is minimized.
It is an overall object of the invention to provide a thermally efficient, protected membrane roofing system which will be permanent that is, will last as long as other major building members.
One preferred embodiment of the invention which is intended to accomplish at least some of the foregoing objects comprises a thermally efficient, protected membrane roofing system comprising an association of interconnected insulating roofing panels. Each panel preferably comprises a laminated composite of an insulating drainage course, a moisture vapor retardant course and a closed cell insulation course. The insulating drainage course comprises a generally homogeneous association of expanded polystyrene spheres which are enrobed with a layer of water proofing material and bonded together at points of contact with random voids created throughout the association to render the course both insulating and substantially porous to the passage of water. The insulating drainage course is operable to be placed on top of a waterproofing membrane. A moisture vapor retardant layer is interposed between the insulating drainage course and a closed cell insulation course and is composed of a material operable to retard the flow of moisture vapor into the closed cell insulation. The insulation course is composed of an expanded polystyrene or similar insulating material and is adhered to the moisture vapor retardant layer to form a laminated, composite panel structure.
The composite panel is operably positioned upon an elasto/plastic or built up water impermeable roofing membrane which is built-up or deposited upon a building roof or deck. The panels are placed edge-to-edge with the insulating drainage course positioned against the water impermeable course of the roofing system. The seams around the panel are then covered with a waterproof tape, which is concomitantly water vapor permeable, to prevent external water from passing into the roofing system while permitting water vapor to exit from beneath the insulation course. An external layer of aggregate, pavers or similar ballast is deposited on top of the insulation course of the panels to maintain the panels in position and to protect the closed cell insulation course from solar degradation, improve fire resistance, prevent wind blow off, etc.
The course of waterproofed expanded polystyrene spheres enables external water, which inadvertently passes downwardly into the system, to rapidly migrate to a conventional drain system. Since occasional water easily passes into and laterally through the first drainage course, the tendency of such water to float the composite panel is minimized.
The initial course also provides a degree of insulation for the underlying water impermeable membrane. The closed cell insulation course, however, has a higher R-rating and provides the primary insulation characteristic of the composite roofing system. The moisture vapor retardant layer isolates the closed cell insulation from water vapor which raises upwardly from vapor within the building structure, or water from the surface of the roofing membrane which, over time, can migrate through the roofing membrane.
The high degree of moisture vapor impermeability of the intermediate vapor barrier layer as compared with the peripheral joints or gaps around the panels, insures that water vapor escapes into the atmosphere around the panels and not through them. This prolongs the life of the insulation course and enhances its insulating characteristics. The waterproof tape physically retains the panels in place and prevents exterior water from freely penetrating the system. It also reduces chances of wind blow off by reducing air passage to the underside of the panel. Any occasional water that does penetrate is rapidly drained away by the insulation drainage course. At the same time the water vapor permeable nature of the tape permits water vapor to escape from the building around the periphery of the insulation panels. Similar advantages may be achieved by tongue and grove panel installation or two layers of unsulation, with joints offset.
In order to decrease the possibility of occasion water penetrating the upper surface of the closed cell insulation layer, this layer may be advantageously sloped toward a water drainage outlet.
US Referenced Citations (8)
Non-Patent Literature Citations (1)
| Entry |
| Sweet's Catalog File 1979, 7.15 Be, pp. 9-11. |
Patent Grant
4719723
