Spray Foam Guide. Recommended enclosure details using open-cell 0.5 pcf and closed-cell 2.0 pcf polyurethane spray foam. in DOE climate zones 1-8

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1 Spray Foam Guide enclosure details using open-cell 0.5 pcf and closed-cell 2.0 pcf polyurethane spray foam in DOE climate zones 1-8 John Straube, Ph.D., P.Eng. Jonathan Smegal Alex Lukachko 2011 Building Science Press

2 Spray Foam Installation Notes All of the spray foam details in this guide assume that all other aspects of the building enclosure are constructed adequately and comply with the building code. It assumes that there is no water intrusion into the enclosure due to poorly constructed water management details. The spray foam manufacturer s guidelines for spraying foam regarding temperatures (air and substrate), moisture content, thickness and fire protection should be adhered to at all times. If it is unclear which construction strategy to use, further guidance should be sought. The IRC and local building codes should be followed at all times unless permission is given otherwise based on sound engineering and physics. The TDS and MSDS should be reviewed and adhered to for the spray foam product(s) being installed. 2

3 Table of Contents 5 Climate Zone Map 6 Application 1: Interior of Foundation Walls in Basements and Conditioned Crawlspaces 8 Application 2: Underside of the Floor Joists in Vented Crawlspaces 10 Application 3: Above Grade Walls 12 Application 4: Vented Attics 14 Application 5: Unvented Attics 16 Application 6: Unvented Cathedral Ceilings 18 Application 7: Vented Cathedral Ceilings 20 Application 8: Floors Over Unconditioned Basements 22 Application 9: Floors Over Exterior Space/Unconditioned Garages 24 Glossary of Terms 3

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5 Climate Zone Map U.S. Department of Energy s Building Energy Codes Program at Pacific Northwest National Laboratory 5

6 Application 1 Interior of Foundation Walls in Basements and Conditioned Crawlspaces Not applicable to vented crawlspaces or foundations; see Application Spray foam installed directly on foundation wall 2. Discussion 2.0 pcf ccspf installed directly against the foundation wall is the preferred option for interior insulation with respect to moisture durability. Another good option in warmer climates is 0.5 pcf ocspf installed directly against the foundation wall, but care needs to be taken to ensure that the vapor permeable spray foam will allow vapor to pass through to the interior, and that there is no bulk water intrusion through the foundation wall. Hybrid applications are also possible: ccspf or ocspf may be installed against the foundation wall, with air and vapor permeable insulation (e.g., batt) installed inboard of that. For a finished basement (i.e., with a wood frame wall), keep the wall framing away from the foundation wall (minimum 1½ ), and fill behind the framing with spray foam. For framed basement walls, see the framed walls section (page 10). The rim joist performs much differently than the foundation wall, and caution must be used with vapor permeable insulation. (They can be considered above grade walls.) Hybrid foundation insulation system General Cautions 1. Insulation R-value should meet N in the 2009 IRC as a minimum. 2. Thermal or ignition barrier requirements as per IRC 2009 R should be followed. 3. Reference: Search for Info-512: Crawlspace Insulation at 4. Reference: Search for Info-511: Basement Insulation at 6

7 Climate Zone Matrix Insulation Type ocspf ccspf Hybrid Caution (Note 1,2) Not Caution (Note 1,2) Caution (Note 1,2) Caution (Note 1) Note 1 Install minimum ccspf, PIR or XPS in contact with exterior wall before application of ocspf. In cold climates, using vapor permeable insulation (ocspf) in the rim joist and in above grade portions of basement walls, may lead to moisture accumulation at the interior surface of the exterior sheathing. A vapor retarding insulation (ccspf, PIR, XPS) should be used adjacent to the basement wall/rim joist in these conditions of such a thickness that the condensation plane (inside face of ccspf, PIR, or XPS) is kept warm to minimize condensation potential from interior relative humidity. Note 2 Do not install any additional vapor barrier on interior of insulation. Because the moisture drive in below-grade walls is always from the exterior to the interior in Zones 6 and lower, installing a low-permeance layer on the interior side of insulation wall will cause moisture related durability issues by trapping moisture in the enclosure and not allowing drying to the interior. The 2009 IRC (R601.3) states that Class I or II vapor retarders are not required on basement walls or the below grade portion of any wall in climate zones 4C, 5, 6, 7 and 8. Note 3 Provide interior space humidity control. It is important for the occupant to control interior RH to reasonable levels (based on the climate zone and season). In very cold climate zones, this may be as low as 35% RH. A functional ventilation system and/or dehumidifier will often be required. 7

8 Application 2 Underside of the Floor Joists in Vented Crawlspaces Spray foam encapsulating floor joist Discussion Vented crawlspaces are not recommended due to the common occurrence of serious moisture related issues and building enclosure failures. However, vented crawlspaces may be mandated in certain areas (flood prone areas) by codes. The floor joists must be kept warm to avoid condensation, mold and rot, so completely encapsulating the floor joists is the safest method of insulating in a vented crawlspace. Hybrid applications are also possible: ccspf or ocspf may be installed against the underside of the floor, with polyisocyanurate, EPS or XPS installed on the underside of the joists with taped joints. If the free vent area is equal to or greater than 1 / 4 of the floor area served, then Application 9 can be used, since the conditions in the vented area will be approximately the same as the exterior conditions. The net free area is the area on a vertical surface unobstructed by walls, screens, louvers, or other materials at the perimeter of the vented space. Hybrid insulation system General Cautions 1. Spray foam exposed in crawlspace may require a thermal or ignition barrier as per IRC and R Reference: Search for BSI-009: New Light in Crawlspaces at 8

9 Climate Zone Matrix Insulation Type ocspf (fully encapsulated joists) Caution (Note 1) Caution (Note 1) Caution (Note 1) Caution (Note 1) ccspf (fully encapsulated joists) Hybrid (spray foam and PIR) Caution (Note 1) Caution (Note 2) Caution (Note 2) Caution (Note 2) Caution (Note 2) Note 1 Vapor Impermeable floor covering prohibited with ocspf. The worst moisture related issues occur when moisture moves through the floor joists towards the interior and is stopped by a vapor impermeable floor covering such as vinyl flooring. In contrast, vapor permeable floor assemblies allow the moisture to safely pass to the interior, where it is removed via air conditioning or a dehumidifier. Doing this minimizes many of the moisture related risks. Similarly, plywood floor sheathing is preferred to OSB floor sheathing because of the increased vapor permeance of plywood. Note 2 Do not install any additional vapor barrier on interior of insulation. Taping the joints is more critical if ocspf is used in the joist space, and slightly less critical if ccspf is used in the joist space. The tape on the joints may fail quickly and installation quality is important. Air leakage and vapor diffusion condensation could be problematic if this system is not maintained. Vapor permeable floor coverings are still recommended to decrease risks. Note 3 Choose a flood-resistant insulation material when applicable. Many of the requirements for vented crawlspaces are in regions which are flood-prone; therefore, the assembly should be designed with this problem in mind. It is generally accepted that closed-cell spray foams have good recoverability from flooding. Only closed-cell foam insulations are considered flood-resistant by FEMA. 9

10 Application 3 Above Grade Walls Spray foam filled wall cavity Discussion Both open-cell and closed-cell spray foam are air impermeable and can help to reduce energy losses and avoid condensation by increasing the airtightness of the enclosure if the enclosure is properly designed and the spray foam is properly installed. Open-cell foam is vapor permeable so care must be taken in colder climates to minimize the risk of vapor diffusion wetting of the exterior sheathing. Hybrid applications, known as flashand-batt or flash-and-fill or combo systems consist of spray foam against the exterior sheathing covered with a layer of fibrous insulation. Spraying foam directly against exterior foam insulation is also possible as a hybrid approach but care must be given during the foam application process. Note that ccspf application against OSB sheathing requires additional considerations (see Note 4). Hybrid insulation system 3. Insulating sheathing and spray foam General Cautions 1. IRC 2009 R601.3 should be referenced for vapor control requirements of wall systems 2. Reference: Search for Info-310: Vapor Control Layer Recommendations at 3. Reference: Search for BSI-038: Mind the Gap, Eh! at 10

11 Climate Zone Matrix Insulation Type Full ocspf Caution (Note 1) Caution (Note 1) Full ccspf Hybrid (ocspf and fibrous) Hybrid (ccspf and fibrous) Hybrid (insulated sheathing and spray foam) Caution (Note 1, 2) Caution (Note 1, 2) Caution (Note 1, 2) Caution (Note 1, 2) Caution (Note 1, 2) Caution (Note 1, 2) Note 1 Vapor control may be required. In cold weather, wintertime vapor condensation wetting of the exterior sheathing is possible with a vapor permeable insulation, so a Class I or Class II vapor control layer is likely required to minimize the moisture related durability risks. Class II vapor control is typically recommended, as Class I (e.g., polyethylene) completely eliminates drying to the interior. Note 2 Ratios of air/vapor impermeable and permeable insulation must be maintained. As the climate gets colder, the R-value ratio of air and vapor impermeable insulation (ccspf, PIR, XPS) to vapor permeable insulation (fiberglass, cellulose, ocspf) must increase to avoid increased risk of condensation on the interior surface of the foam (as per IRC 2009 R601.3). For example, in climate zone 6, IRC R601.3 specifies a minimum of R-7.5 exterior of a 2x4 wall (R-13), and R exterior of a 2x6 (R-19) wall to minimize the risk of condensation. This means that 37% of the total installed R-value should be vapor and air impermeable. So in a 2x6 wall in climate zone 6, with a desired total R-value of R-20, a minimum of R-5.6 should be in the form of closed cell spray foam and R-14 in the form of fibrous air and vapor permeable insulation. Note 3 Provide interior space humidity control. It is important for the occupant to control interior RH to reasonable levels (based on the climate zone and season). In very cold climate zones, this may be as low as 35% RH. A functional ventilation system and/or dehumidifier will often be required. Note 4 Add a drainage gap when ccspf is applied to OSB sheathing. OSB has limited moisture tolerance, and ccspf eliminates redistribution and drying to the interior. To make up for these issues, install exterior cladding with a drainage gap ( 3 / 8 minimum recommended) between the cladding and water resistive barrier. 11

12 Application 4 Vented Attics Attic insulated entirely with spray foam Hybrid insulation system 3. Ductwork installed with Hybrid insulation system Discussion Many attic moisture and energy problems are the result of air leakage from the interior space into the attic. This can result in condensation in cold climates, and significant energy losses in all climates as well as other performance problems. By using spray foam or a hybrid approach of spray foam and fibrous insulation (cellulose, fiberglass) the air leakage into the attic can be significantly reduced or eliminated, resulting in decreased energy losses and fewer moisture problems. It is recommended that mechanical space conditioning equipment and ductwork only be installed in conditioned space. If ducts are placed in the attic, SPF can be used to airseal. General Cautions 1. Insulation R-value should meet N in the 2009 IRC as a minimum. 2. Spray foam exposed in attic may require a thermal or ignition barrier as per IRC 2009 R Combustible insulation clearance of 3 as per 2009 IRC R especially around lighting or chimneys. 4. Ductwork insulation must follow IRC

13 Climate Zone Matrix Insulation Type Full ocspf Full ccspf Hybrid Note 1 Ensure adequate attic ventilation. It is likely that some moisture will still reach the attic either by air leakage or vapor diffusion. In a properly vented attic, this moisture will be carried away without causing any problems. Note 2 A polyethylene vapor barrier is not required but an air barrier is required. Research, simulations and field observations show that a polyethylene vapor barrier is not required to control vapor diffusion into the attic since vapor diffusion moves so slowly and attic ventilation will remove the moisture. Condensation could occur if air leakage occurs from the interior into the attic in cold weather, but this issue can be reduced or eliminated with either a fully spray foamed attic or a hybrid attic approach. 13

14 Application 5 Unvented Attics Spray foam filled cavity Discussion Both open-cell and closed-cell spray foam are air impermeable and may help to reduce energy losses by increasing the airtightness of the enclosure when properly installed. Open-cell foam is quite vapor permeable so care must be taken in colder climates to minimize the risk of vapor diffusion wetting of the exterior sheathing. Hybrid applications, known as flash-andbatt or flash-and-fill consist of spray foam against the roof sheathing as well as a layer of fibrous insulation (fiberglass or netted cellulose). In some cases, board foam insulation can be installed on the exterior of the roof deck to decrease thermal bridging, and increase the R-value and durability of the roof system. Thermal bridging can be controlled by spraying over the inside at the rafters. Hybrid insulation system 3. Insulating sheathing and spray foam General Cautions 1. Minimum insulation R-value should meet N in the 2009 IRC. 2. Unvented attic assemblies should meet the conditions in IRC 2009 R806.4 as a minimum. 3. Spray foam exposed in attic may require a thermal barrier or ignition barrier as per IRC 2009 R Combustible insulation clearance of 3 as per 2009 IRC R especially around lighting or chimneys. 5. Reference: Search for BSD-102: Understanding Attic Ventilation at 6. Reference: Search for IRC FAQ: Conditioned Attics at 7. Reference: Search for BSD-149: Unvented Roof Assemblies for all Climates at 14

15 Climate Zone Matrix Insulation Type Full ocspf Caution (Note 1) Caution (Note 1) Not Full ccspf Hybrid (ocspf and fibrous) Hybrid (ccspf and fibrous) Insulating sheathing and spray foam Caution (Note 1) Not Not Caution (Note 2) Caution (Note 2) Caution (Note 2 for ocspf) Caution (Note 2 for ocspf) Note 1 Vapor control may be required. In cold climates, vapor condensation wetting of the roof sheathing is possible with a vapor permeable ocspf insulation, and a Class I or Class II vapor control layer is likely required to minimize the moisture related durability risks. Class II vapor control is typically recommended, as Class I (e.g., polyethylene) completely eliminates drying to the interior. Some advertised vapor barrier paints (Class II) may adequately control vapor diffusion. Note 2 R-value ratios of air/vapor impermeable and permeable insulation must be maintained. As the climate zone gets colder, the ratio of air impermeable insulation (cc- SPF, PIR, XPS) to air permeable insulation (fiberglass, cellulose) must increase to avoid condensation on the interior surface of the impermeable foam. See IRC 2009 Unvented Attics section 806.4, Table Note 3 Provide interior space humidity control. It is important for the occupant to control interior RH to reasonable levels (based on the climate zone and season). In very cold climate zones, this may be as low as 35% RH. A functional ventilation system and/or dehumidifier will often be required. 15

16 Application 6 Unvented Cathedral Ceilings Spray foam filled cavity Discussion Both open-cell and closed-cell spray foam are air impermeable and may help to reduce energy losses by increasing the airtightness of the enclosure when properly installed. Open-cell foam is quite vapor permeable so care must be taken in colder climates to minimize the risk of vapor diffusion wetting of the exterior sheathing. Hybrid applications, known as flash-andbatt or flash-and-fill consist of spray foam against the roof sheathing as well as a layer of fibrous insulation (fiberglass or netted cellulose). Board foam insulation (XPS, PIR, high-density EPS) can be installed on the exterior of the roof deck to increase the R-value and durability of the roof system. Exterior insulation keeps the enclosure warmer and less prone to winter time condensation in cold climates. Hybrid insulation system 3. Insulating sheathing and spray foam General Cautions 1. Minimum insulation R-value should meet N in the 2009 IRC. 2. Reference: Search for IRC FAQ: Conditioned Attics at 3. Reference: Search for BSD-149: Unvented Roof Assemblies for all Climates at 16

17 Climate Zone Matrix Insulation Type Full ocspf (Note 3) Caution (Note 1, 3) Caution (Note 1, 3) Not Full ccspf Hybrid (ocspf and fibrous) (Note 3) Caution (Note 1, 3) Not Not Hybrid (ccspf and fibrous) Insulating sheathing and spray foam Caution (Note 2) Caution (Note 2) Caution (Note 2, 3) Caution (Note 2, 3) Note 1 Vapor control may be required. In cold climates vapor condensation wetting of the roof sheathing is possible with a vapor permeable ocspf insulation, and a Class I or Class II vapor control layer is likely required to minimize the moisture related durability risks. Class II vapor control is typically recommended, as Class I (e.g., polyethylene) completely eliminates drying to the interior. Night sky radiation may increase the risk of condensation on the sheathing more than in walls of the same enclosure because of lower roof sheathing temperatures caused by long wave radiation emission heat loss from the roof to the sky on a clear night. Note 2 Ratios of impermeable and permeable insulation must be maintained. As the climate zone gets colder, the ratio of air impermeable insulation (closed-cell spray foam, PIR, XPS) to air permeable insulation (fiberglass, cellulose) must increase to avoid condensation on the interior surface of the foam. Designing for the condensation point to occur in the middle of the closed-cell spray foam or insulating sheathing is ideal so that condensation will not occur on the interior surface of the impermeable insulation. Note 3 Provide interior space humidity control. It is important for the occupant to control interior RH to reasonable levels (based on the climate zone and season). In very cold climate zones, this may be as low as 35% RH. A functional ventilation system and/or dehumidifier will often be required. 17

18 Application 7 Vented Cathedral Ceilings Vented Cathedralized Attic 1. Vented cathedral ceiling with framing lumber rafters 2. Vented cathedral ceiling with I-joists Discussion Vented cathedral ceilings require some form of backer board to act as a substrate for the spray foam while still maintaining an air gap against the roof sheathing. In a ceiling that uses framing lumber, blocking can be used next to the joists, running along the entire joist or just at discrete connection points. In a ceiling with engineering I-joists, the backer board can be attached directly to the top flange of the joist. To increase the R-value and vapor control of an open-cell spray foam system, the backer board could be a rigid board insulation product such as XPS, PIR or high-density EPS, assuming the boards are compatible with the spray foam. In general, unvented cathedrals are recommended instead, but in some cases are not allowed. One compromise is to insulate directly to the underside of the roof sheathing, and vent above the roof sheathing, below the cladding, as with a metal or tile clad roof. 3. Hybrid vented cathedral ceiling General Cautions 1. Minimum insulation R-value should meet N in the 2009 IRC. 2. Reference: Search for BSD-149: Unvented Roof Assemblies for all Climates at 18

19 Climate Zone Matrix Insulation Type Full ocspf Caution (Note 1, 2, 3) Caution (Note 1, 2, 3) Not Full ccspf (Note 3) (Note 3) (Note 3) Hybrid (ocspf and fibrous) Caution (Note 1, 2, 3) Not Not Hybrid (ccspf and fibrous) (Note 3) Caution (Note 2, 3) Caution (Note 2, 3) Note 1 Vapor control may be required. In cold climates vapor condensation wetting of the roof sheathing is possible with a vapor permeable ocspf insulation, and a Class I or Class II vapor control layer is likely required to minimize the moisture related durability risks. Night sky radiation may increase the risk of condensation on the sheathing more so than in walls of the same enclosure. Foam board insulation could be used as the backer for ocspf to minimize moisture related issues. Note 2 Ratios of impermeable and permeable insulation must be maintained. As the climate zone gets colder, the ratio of air and vapor impermeable insulation (closed-cell spray foam, PIR, XPS) to air and vapor permeable insulation (fiberglass, cellulose) must increase to avoid condensation on the interior surface of the foam. Designing for the condensation point to occur in the middle of the closed-cell spray foam or insulating sheathing is ideal so that condensation will not occur on the interior surface. Note 3 Provide interior space humidity control. It is important for the occupant to control interior RH to reasonable levels (based on the climate zone and season). In very cold climate zones, this may be as low as 35% RH. A functional ventilation system and/or dehumidifier will often be required. 19

20 Application 8 Floors Over Unconditioned Basements Spray foam between floor joists Hybrid insulation system Discussion Insulating the floor between the unconditioned basement and the rest of the building is not recommended. There is a significant increase in the risk of moisture related issues to the basement and the rest of the building. Mechanical equipment is often in the basement, and this should always be brought in conditioned space to minimize energy losses and decrease the risk of health related issues caused by excessive moisture (e.g., leaky ductwork). See Application 1 on page 8 to see much better options for insulating basements using spray foam. General Cautions 1. Minimum insulation R-value should meet N in the 2009 IRC. 2. Exposed spray foam may require a thermal barrier as per IRC 2009 R Reference: Search for BSD-103: Understanding Basements at 20

21 Climate Zone Matrix Insulation Type ocspf (fully encapsulated joists) Caution (Note 1, 3) Caution (Note 1, 3) Caution (Note 3) Caution (Note 3) ccspf (fully encapsulated joists) Hybrid (spray foam and board foam) Caution (Note 3) Caution (Note 3) Caution (Note 3) Caution (Note 3) Caution (Note 2, 3) Caution (Note 2, 3) Caution (Note 2, 3) Caution (Note 2, 3) Note 1 Vapor impermeable floor covering prohibited with ocspf. In warmer climates, the worst moisture related issues occur when moisture moves through the floor joists towards the interior and is stopped by a vapor impermeable floor covering such as vinyl flooring. In contrast, vapor permeable floor assemblies allow the moisture to safely pass to the interior, where it is removed via air conditioning or a dehumidifier. Doing this minimizes many of the moisture related risks. Note 2 Taping joints in board insulation. Taping the joints is more critical if ocspf is used in the joist space, and slightly less critical if ccspf is used in the joist space. Often times the tape on the joints will fail quickly, especially if installed on the downward-facing surface. Air leakage and vapor diffusion condensation could be problematic if this system is not maintained. Vapor permeable floor coverings are still recommended to decrease inherent risks. Note 3 Provide humidity control to maintain <50% RH. It is critical to health and building durability to manage the moisture in the basement especially if the space conditioning equipment is located there. In very cold climate zones, this may be as low as 35% RH. More than one dehumidifier may be required. 21

22 Application 9 Floors Over Exterior Space/Unconditioned Garages Spray foam between floor joists Hybrid insulation system Discussion Spray foam can be used in floors over exterior spaces, such as houses on piles, cantilevered floors on any level, and in unconditioned garage ceilings. Because of the air barrier characteristic of spray foam, it performs very well in garage ceilings and cantilevered floors where air movement can result in energy losses, comfort issues, and potential indoor air quality issues (often there are unintentional air flow pathways between the garage and the interior space). The proper amount and location of vapor diffusion control is required in both hot and cold climates to minimize moisture related issues. Spray foam beneath houses that are open to the outdoors should be protected against insects and small animals. General Cautions 1. Minimum insulation R-value should meet N in the 2009 IRC. 2. Exposed spray foam may require a thermal barrier as per IRC 2009 R Termite protection should follow 2009 IRC R

23 Climate Zone Matrix Insulation Type ocspf Caution (Note 1,2) Caution (Note 1, 2) Caution (Note 2) Caution (Note 2) ccspf (Note 2) (Note 2) (Note 2) (Note 2) Hybrid (ocspf and fibrous) Caution (Note 1, 2, 3) Caution (Note 1, 2, 3) Caution (Note 2) Caution (Note 2) Hybrid (ccspf and fibrous) Caution (Note 3) Caution (Note 3) (Note 2) (Note 2) Note 1 Vapor control in hot-climates. In warm-humid climates, vapor control may be required on the exterior to avoid condensation at the colder interior surfaces due to air conditioning. These issues can be minimized by using vapor permeable interior surfaces. Note 2 Underneath buildings. Spray foam exposed to the outdoors should be protected against insects and vermin as per the spray foam manufacturers recommendations, and local building codes. Note 3 Sufficient spray foam. In the hybrid insulation system, sufficient spray foam should be used so that the exterior surface of the foam is warm enough to prevent condensation in warm-humid climates. 23

24 Glossary of Terms Air Barrier System Air barriers are three-dimensional systems of materials designed, constructed, and/or acting to control air flow across a building enclosure, or between a conditioned space and an unconditioned space. In multi-unit/townhouse/apartment construction an air barrier system should also separate the conditioned air from any given unit and adjacent units. The pressure boundary of the enclosure should, by definition, be coincident with the plane of a functional air barrier system. In multi-unit/townhouse/apartment construction the air barrier system may also be the fire barrier and smoke barrier between units. In such assemblies the air barrier system must also meet the specific fire resistance rating requirement for the given separation. Air barrier systems are assembled from materials incorporated in assemblies (or components such as windows) that are interconnected to create enclosures. Each of these three elements has measurable resistance to air flow. The minimum recommended resistance or air permeance for the three components are: Material 0.02 l/(s-m 2 )@ 75 Pa (0.004 cfm/ft 0.3 WC) Assembly 0.20 l/(s-m 2 )@ 75 Pa (0.04 cfm/ft 0.3 WC) Enclosure 2.00 l/(s-m 2 )@ 75 Pa (0.4 cfm/ft 0.3 WC) Materials and assemblies that meet these performance requirements are said to be air barrier materials and air barrier assemblies. Air barrier materials incorporated in air barrier assemblies that in turn are interconnected to create enclosures are called air barrier systems. Air-impermeable Insulation An insulation having an air permeance equal to or less than 0.02 L/s m 2 at 75 Pa pressure differential tested according to ASTM E 2178 or E 283. Ignition Barrier The following materials are defined as ignition barriers by the 2009 IRC Section R316: ½-inch-thick (38 mm) mineral fiber insulation; 3.2. ¼-inch-thick (6.4 mm) wood structural panels; / 8-inch (9.5 mm) particleboard; 3.4. ¼-inch (6.4 mm) hardboard; / 8-inch (9.5 mm) gypsum board; or 3.6. Corrosion-resistant steel having a base metal thickness of inch (0.406 mm) 24

25 R-value; Thermal Resistance Quantitative measure of resistance to heat flow or conductivity, the reciprocal of U-factor. The units for R-value are ft 2 F hr/btu (English) or m 2 K hr/w (SI or metric). While many in the building community consider R-value to be the primary or paramount indicator of energy efficiency, it only deals conduction, one of three modes of heat flow, (the other two being convection and radiation). As an example of the context in to which R-value should be placed, 25% to 40% of a typical home s energy use can be attributed to air infiltration. Thermal Barrier A thermal or fire barrier is a material or coating, applied over polyurethane foam, designed to slow the temperature increase of the foam during a fire, and to delay the foam s involvement in a fire. Such thermal barriers limit the temperature rise of the underlying polyurethane foam to not more than 250 F after 15 minutes of fire exposure complying with the standard time temperature curve of ASTM E 119 or UL 263. The thermal barrier shall be installed in such a manner that it will remain in place for 15 minutes based on NFPA 286 with the acceptance criteria of Section R , FM 4880, UL 1040 or UL1715. Vapor Retarder Class A measure of the ability of a material or assembly to limit the amount of moisture vapor that passes through that material or assembly. Vapor retarder class shall be defined using the desiccant method with Procedure A of ASTM E 96 as follows: Class I: 0.1 perm or less Class II: 0.1 < perm ; 1.0 perm Class Ill: 1.0 < perm ; 10 perm 25