Extruded polystyrene insulation provides one of a kind properties that differentiate it from other styles of foam plastic insulation and therefore make it ideal for a number of roof designs.
Extruded polystyrene insulation offers different properties that differentiate that from other styles of foam plastic insulation and therefore make it ideal for several roof designs.
Sometimes considered "the other roof insulation, " XPS is specified when higher compressive strength generally, higher water resistance and higher thermal resistance in the presence of water are needed. Those features make XPS the most well-liked choice in green-planted roof systems, inverted or secured membrane plaza deck systems, white or "great" single-ply metal and roofing roofing systems.
When contemplating sustainable, sturdy roofing designs it's important to start with how water-resistant an insulation material is. Extruded polystyrene is without question manufactured to comply with ASTM C578, "Regular Specification for Rigid, Cellular Polystyrene Thermal Insulation." ASTM C578 is the primary reference standard used for specifying polystyrene insulations also, signifying it defines physical real estate for both extruded polystyrene and expanded polystyrene.
You can find fundamental differences between the properties of XPS and EPS, which are critical to understanding why XPS is fantastic for applications that require high resistance to moisture intrusion. Normal water absorption by total immersion for XPS is listed at 0.3 percent optimum by volume, compared to 2.0 to 4.0 percent for EPS, depending on its density. The quantity of drinking water absorption is definitely a function of the composition of each material.
The homogeneous and hydrophobic closed-cell structure of XPS helps it be resistant to water intrusion. This is a significant contrast in comparison with the make-up of an EPS panel. Although EPS beads are closed-cell and hydrophobic, the beads are also surrounded by voids. These voids are in charge of the bigger water absorption volume within the finished EPS panel. The blowing agent used in EPS is quickly substituted by oxygen and paired together with these voids the effect 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 a rise in thermal resistance.
Polyisocyanurate rigid insulation is manufactured to comply with ASTM C1289, "Typical Specification for Faced Rigid Cellular Polyisocyanurate Thermal Insulation Table." Polyiso chemistry will involve monomers that are hydrophilic. The cell structure is commonly irregular in form and size and less defined in comparison to XPS. Because of these dissimilarities, polyiso has higher drinking water absorption than XPS - 1 to 2 2 percent by quantity, according to the classification and type, which compares to XPS at 0.3 percent. Likewise, it is important to note that the polyiso common requires a test approach that measures water absorption following a two-hour immersion in normal water and 10-minute drain period, versus the XPS test method that uses a 24 hour immersion and requires no drain period.
Truly "green" roofs have become more common, particularly in dense cities. You can find two basic types of green roofs - intensive and extensive. Extensive and intensive roofs differ in cost, depth of growing media and the decision of plants.
Comprehensive roof cover media varies in depth 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 in . with a weight increase of between 60 pounds per square ft . to 200 pounds per square foot when saturated. Green roofs provide a thermal mass effect, 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 can significantly reduce heat flow into a building, thus lowering the load placed on air conditioning equipment.
The highly water resistant characteristic of XPS roof insulation actually "enables" green roof construction. Green roofs are typically constructed within an inverted configuration, and therefore the insulation is along with the waterproofing membrane rather than under it as in traditional roof systems. An eternity of exposure to retained water helps it be crucial that the insulation used retains R-value, possesses compressive strength and other critical properties while subjected to water. For that reason, XPS is almost used to insulate lawn roofs exclusively. When specifying, one can choose from XPS ASTM C578 Type VI, VII or V to very best fit the design requirements of that roof.
XPS is also durable, making it reusable when removal and reinstallation are necessary for repairs. For many of these features, XPS is the only insulation recommended for yard roof systems in the NRCA Green Roof Systems Manual, 2007 Edition.
LEED defines "amazing roofs" as roofing floors or systems that reduce warmth islands. A high temperature island is a created area that has a significant temperatures difference in comparison to adjacent undeveloped areas. The LEED-NC 2.2 cool roof definition includes roofs that are either green/vegetated, as already discussed, or roof surfaces with a Solar Reflectance Index equal to or greater than 78.
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Common cool roof single-ply membranes include thermoplastic olefin (TPO) and polyvinyl chloride. Both materials can be found in white readily, which makes them a very affordable option for make use of with XPS roofing insulation in both latest and reroof applications.
XPS is generally used under all types and colors of single-ply roofing membranes but it should be protected from solar warmth by a cover board when used under non-white membranes in new construction and reroofing with total tear-off. In those applications, a cover board must be placed on the XPS to split up it from the membrane. Dark-membrane-to-XPS interface temperature ranges can way 190 to 200 degrees Fahrenheit, which exceeds the suggested service heat range of 165 degrees Fahrenheit for XPS. Therefore a cover plank is needed to individual the dark membrane from XPS. Common cover boards used less than dark membranes include high-density wood water or fiber resistant gypsum table.
Mechanically attached TPO and PVC membranes require only a cheap slip-sheet separation from XPS. The slip-sheet is needed to achieve a Class A (ASTM E10 cool fire rating with TPO, or even to chemically individual PVC from the XPS (see Figure 5).
These systems may also be installed "direct to deck" lacking any underlying gypsum board thermal barrier layer. Because the mid-1990s, XPS roof insulation systems have already been shown at Underwriters Laboratories (UL) for direct-to-steel roof deck application (see UL Roof Deck Building numbers 440 and 457). The listed roof deck systems were examined for flame spread beneath the steel roofing deck (not really hourly rated) relative to UL Standard 1256 as referenced in Section 2603.4.1.5 of the 2006 International Building Code.
XPS roof insulation types X, IV and V are generally used with mechanically attached interesting white roofing membranes and a simple slip-sheet. XPS and the white membrane, mounted to the steel roof deck straight, combine to create 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 level of resistance to endure the inevitable roof leaks that arise as roofs age. XPS will maintain steadily its properties in the presence of water in the event that leaks develop on the existence of the building, rendering it reusable following leaks are repaired as well. Water-resistant insulation means the roofing system will preserve its R-value and energy preservation power even when exposed to moisture from leaks. Water resistance does mean retention of compressive strength and retention of tensile load on roofing system fasteners, holding the roofing secure until maintenance are finished. Reusable insulation means decreased tear-off materials taken to landfills.
Metal roofing systems depend on XPS insulation to supply high compressive power for a well balanced substrate to properly chair the base of clips used to attach the roof, and for water resistance to provide a second water barrier under the roofing panels.
ASTM C578 Type IV XPS insulation has excellent compressive power for mounting standing-seam steel roof panels. Compressive resistance establishes initial 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 surface of the insulation, and without adhered facing material you don't have to trim around the clip for right seating, saving cost and labor. A recent examination of an XPS insulated steel roof, after a decade in service under steel roofing clips uncovered clip stability and continuing fastener load retention.
The National Roofing Contractors Association recommends a layer of asphalt-saturated felt between the insulation layer and standing seam metal roof to supply a drainage plane in buildings with high prospect of condensation. The NRCA Roofing and Waterproofing Manual recommends utilizing a vapor retarder with a permeation rating of 0.5 perms or less in certain climate zones. When installed with sealed joints, highly water-resilient XPS insulation eliminates the need for these additional layers.
The water resistance of XPS also enables more flexible job staging. It is not uncommon for various components of the roof assembly to have delayed delivery. XPS insulation can be installed continuously and sealed accompanied by the metal roofing as the schedule permits. Manufacturers of XPS usually do not need that the insulation board be covered or secured since it is installed because of its resistance to work site water absorption. It is common practice for XPS insulation, with sealed joints, to serve as a temporary roofing when delivery of the standing-seam roofing is delayed. After 30 to 60 days, based on the strength of UV exposure, XPS insulation board can start to fade in color. And while exposed XPS makes a good temporary water-resistant covering, it isn't intended to remain uncovered for extended periods of time.
Standing seam metal roofing systems that are installed directly above XPS insulation can perform a Class A ranking. Consult UL listings for finished details and specific product listings. XPS insulation is also UL Fire Classified with metal roof covering systems for installation direct to structural steel roof deck without an underlying thermal barrier. XPS insulation is not recommended for use immediately under black steel or copper roofs because of potential warmth absorption generating temperatures more than the maximum XPS service temperature. When specifying black metallic or copper roofing panels, a minimum thickness of 1/4-inch moisture resistant gypsum board is recommended between your XPS insulation and metal roof.
ASTM E119 may be the test approach that determines the timed structural fire level of resistance of a roof assembly. Steel roof deck assemblies insulated with any kind of foam plastic insulation generally require some type of fire resistant layer to attain an hourly ranking. When XPS insulation is used in an hourly ranked assembly, a level of 5/8-in . type X gypsum board should be installed on top of the steel deck relative to the particular UL assembly specification. Alternate safeguards layers instead of, or furthermore to, gypsum board can include sprayed fibrous or cementitious coatings put on the bottom side of the metal deck. Concrete roof decks are inherently even more fire resistant than metal and have a different set of criteria for score. Find specific assembly listings for the total amount and form of protection required.