Extruded polystyrene insulation offers exclusive properties that differentiate that from other styles of foam plastic insulation and therefore make it perfect for a number of roof designs.
Extruded polystyrene insulation offers exceptional properties that differentiate that from other types of foam plastic insulation and therefore make it ideal for a number of roof designs.
Considered "the other roofing insulation sometimes, " XPS is specified when higher compressive strength generally, higher water resistance and higher thermal resistance found in the presence of water are needed. Those features make XPS the most well-liked choice in green-planted roof systems, protected or inverted membrane plaza deck systems, white or "awesome" single-ply roofing and metal roofing systems.
When considering sustainable, sturdy roofing designs it's vital that you start with how water-resistant an insulation materials is. Extruded polystyrene is definitely manufactured to comply with ASTM C578, "Common Specification for Rigid, Cellular Polystyrene Thermal Insulation." ASTM C578 can be the primary reference standard used for specifying polystyrene insulations, meaning it defines physical homes for both extruded polystyrene and expanded polystyrene.
There are fundamental differences between the properties of XPS and EPS, which are critical to understanding why XPS is ideal for applications that require high resistance to moisture intrusion. Normal water absorption by total immersion for XPS is normally detailed at 0.3 percent maximum by volume, in comparison to 2.0 to 4.0 percent for EPS, depending on its density. The number of water absorption is without question a function of the composition of each material.
The hydrophobic and homogeneous closed-cell structure of XPS makes it resistant to water intrusion. This is a major contrast in comparison with the makeup of an EPS board. Although EPS beads happen to be hydrophobic and closed-cell, the beads are also surrounded by voids. These voids are in charge of the bigger water absorption volume within the finished EPS plank. The blowing agent found in EPS is without question quickly replaced by weather and paired together with these voids the result is an EPS insulation product with lower thermal level of resistance characteristics when compared to XPS. As EPS density increases, these voids lower, yielding less prospect of water absorption and an increase in thermal resistance.
Polyisocyanurate rigid insulation is manufactured to adhere to ASTM C1289, "Typical Specification for Faced Rigid Cellular Polyisocyanurate Thermal Insulation Plank." Polyiso chemistry calls for monomers which are hydrophilic. The cell composition is commonly irregular in proportions and shape and less defined in comparison to XPS. Because of these variances, polyiso has higher normal water absorption than XPS - one to two 2 percent by quantity, according to the type and classification, which comes even close to XPS at 0.3 percent. Likewise, you should remember that the polyiso typical requires a test technique that measures normal water absorption after a two-hour immersion in drinking water and 10-minute drain period, versus the XPS test method that runs on the 24 hour immersion and requires no drain time.
Truly "green" roofs are becoming more common, in dense urban areas particularly. You can find two basic types of green roofs - intensive and extensive. Intensive and considerable roofs differ in cost, depth of growing media and the decision of plants.
In depth roof cover media varies comprehensive between 2 inches and 6 inches with a weight increase of between 16 pounds per square foot to 35 pounds per square foot when saturated. Intensive green roofing cover media varies in depth between 8 inches and 24 inches with a weight increase of between 60 pounds per square ft . to 200 pounds per square ft . when saturated. Green roofs provide a thermal mass impact, which in turn saves energy and provides reduced heating and cooling costs. Other rewards include reduced normal water runoff, expanded useful existence of the roof, and added beauty and useable space.
Foremost among the many sustainability objectives of a green roof are to retain water and reduce storm water discharge, and to conserve energy through the cooling and shading properties of soil and plantings that may drastically reduce heat flow into a building, lowering the load placed on air conditioning equipment thus.
The highly water resistant characteristic of XPS roof insulation actually "enables" green roof construction. Green roofs are constructed in an inverted configuration typically, and therefore the insulation is on top of the waterproofing membrane instead of under it as in traditional roof systems. An eternity of contact with retained water makes it imperative that the insulation employed retains R-value, possesses compressive strength and other critical properties while exposed to water. For that good reason, XPS is almost solely used to insulate garden roofs. When specifying, one can choose from XPS ASTM C578 Type VI, V or vii to most effective fit the look requirements of this roof.
XPS is durable also, making it reusable when removal and reinstallation are needed for repairs. For all of these features, XPS is the only insulation recommended for yard roof systems in the NRCA Green Roof Systems Manual, 2007 Edition.
LEED defines "interesting roofs" as roofing floors or perhaps systems that reduce heat islands. A heating island is a created area that has a significant temperature difference in comparison to adjacent undeveloped areas. The LEED-NC 2.2 cool roof definition includes roofs which are either green/vegetated, as already discussed, or roof surfaces with a Solar Reflectance Index equal to or greater than 78.
Common cool roofing single-ply membranes include thermoplastic olefin (TPO) and polyvinyl chloride. Both materials are available in white readily, which makes them an extremely affordable option for make use of with XPS roofing insulation in both brand-new and reroof applications.
XPS is generally used under all sorts and colors of single-ply roofing membranes but it must be protected from solar heat by a cover board when used under nonwhite membranes in new engineering and reroofing with total tear-off. In those applications, a cover board should be placed on the XPS to split up it from the membrane. Dark-membrane-to-XPS interface temperatures can strategy 190 to 200 degrees Fahrenheit, which exceeds the advised service temperature of 165 degrees Fahrenheit for XPS. As a result a cover plank is needed to individual the dark membrane from XPS. Common go over boards utilized under dark membranes incorporate high-density real wood fiber or water-resistant gypsum board.
Mechanically attached TPO and PVC membranes require only a cheap slip-sheet separation from XPS. The slip-sheet is required to achieve a Class A (ASTM E10 cool fire ranking with TPO, or even to chemically individual PVC from the XPS (see Figure 5).
These systems can also be installed "immediate to deck" without an underlying gypsum board thermal barrier layer. Because the mid-1990s, XPS roof insulation systems have been stated at Underwriters Laboratories (UL) for direct-to-steel roofing deck application (watch UL Roof Deck Development numbers 440 and 457). The listed roofing deck systems were analyzed for flame spread beneath the steel roof deck (not really hourly rated) relative to UL Standard 1256 as referenced in Section 2603.4.1.5 of the 2006 International Construction Code.
XPS roof insulation types X, IV and V are commonly used with mechanically attached awesome white roofing membranes and a straightforward slip-sheet. XPS and the white membrane, installed directly to the steel roof deck, combine to produce a sustainable roofing system highly. Superior SRI is achieved, while material installation and use labor is minimized as cover boards and underlying thermal barrier layers are eliminated.
Beyond those immediate benefits, life-routine price is minimized with XPS that has the drinking water resistance to endure the inevitable roof leaks that appear as roofs age. XPS will maintain steadily its properties in the presence of water in the event that leaks develop over the life of the building, as well rendering it reusable after leakages are repaired. Water resistant insulation means the roofing system will retain its R-value and energy preservation power even when exposed to moisture from leakages. Water resistance does mean retention of compressive strength and retention of tensile load on roof structure system fasteners, holding the roofing secure until fixes are finished. Reusable insulation means decreased tear-off materials taken to landfills.
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Metal roofing systems rely on XPS insulation to supply high compressive durability for a stable substrate to properly chair the bottom of clips used to attach the roof, and for water resistance to provide a second water barrier beneath the roofing panels.
ASTM C578 Type IV XPS insulation has excellent compressive power for mounting standing-seam metallic roof panels. Compressive resistance establishes first fastener minimizes and load long-term creep to keep fastener load retention over time. The XPS surface is versatile enough to allow the clips to chair properly in the top of insulation, and without adhered facing material there is no need to trim around the clip for appropriate seating, saving cost and labor. A recent study of an XPS insulated metallic roof, after a decade in service under steel roofing clips uncovered clip stability and continued fastener load retention.
The National Roofing Contractors Association recommends a layer of asphalt-saturated felt between your insulation layer and standing seam metal roof to provide a drainage plane in buildings with high potential for condensation. The NRCA Waterproofing and Roofing Manual recommends utilizing a vapor retarder with a permeation rating of 0.5 perms or less in certain climate zones. When set up with sealed joints, water-resilient XPS insulation eliminates the need for these additional layers highly.
The water resistance of XPS enables more flexible job staging also. It isn't uncommon for various elements of the roofing assembly to have delayed delivery. XPS insulation could be installed continuously and sealed accompanied by the metal roofing as the schedule permits. Manufacturers of XPS do not need that the insulation plank be covered or covered as it is installed due to its resistance to task site water absorption. It's quite common practice for XPS insulation, with sealed joints, to provide as a temporary roof when delivery of the standing-seam roofing is delayed. After 30 to 60 days, according to the intensity of UV exposure, XPS insulation board may begin to fade in color. And while exposed XPS produces a good temporary water resistant covering, it is not intended to remain exposed for extended periods of time.
Standing seam steel roofing systems that are installed more than XPS insulation can achieve a Class A ranking directly. Consult UL listings for whole details and specific product listings. XPS insulation is also UL Fire Categorized with metal roof covering systems for installation immediate to structural steel roofing deck without an underlying thermal barrier. XPS insulation is not recommended for use directly under black metal or copper roofs due to potential heat absorption generating temperatures in excess of the maximum XPS service temperature. When specifying black metallic or copper roof panels, the very least thickness of 1/4-inch moisture tolerant gypsum board is recommended between your XPS insulation and metal roof.
ASTM E119 may be the test method that determines the timed structural fire level of resistance of a roofing assembly. Steel roofing deck assemblies insulated with any sort of foam plastic insulation generally require some form of fire resistant coating to attain an hourly ranking. When XPS insulation can be used in an hourly ranked assembly, a coating of 5/8-inches type X gypsum board must be installed together with the steel deck in accordance with this UL assembly specification. Alternate protection layers in lieu of, or furthermore to, gypsum board may include sprayed cementitious or fibrous coatings put on the bottom side of the metal deck. Concrete roof decks are inherently even more fire resistant than steel and have a different group of criteria for rating. Look at specific assembly listings for the proper execution and amount of security required.
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