Insulation e book by PG Designs

Thermal Moisture Protection:

Insulation

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Contents Part One Specifying Polyiso for Continuous Insulation in Walls

By Jared O. Blum

Part Two Specifying Reflective Insulation

By David W. Yarbrough, PhD, PE

Part Three Insulationâ&#x20AC;&#x2122;s Role in Controlling Noise

By Stacy Fitzgerald-Redd

Part Four The Effect of Temperature on Insulation Performance

by Christopher Schumacher, M.A.Sc.

Part Five Thermal Barriers and the Protection of Foamed Plastic By John A. Dalton

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Part One Specifying Polyiso for Continuous Insulation in Walls

BY JARED O. BLUM

Jared O. Blum is the president of the Polyisocyanurate Insulation Manufacturers Association (PIMA), which is the North American trade association representing manufacturers of polyiso foam insulation. He can be reached via e-mail at joblum@pima.org.

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All images courtesy Polyisocyanurate Insulation Manufacturers Association

Specifying Polyiso for Continuous Insulation in Walls Architects, specifiers, and building owners are striving to advance the way commercial and residential building envelopes are developed, in response to more stringent policies for energy conservation. Continuous insulation (ci) is prominently featured as a solution because it is an effective means of addressing these challenges.

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Figure 1 Wood Framing Continuous Insulation (Polyiso) Cavity Insulation

Cladding (Lap Siding Shown)

Continuous Masonry Insulation or Concrete Poly

iso

Steel Framing Cavity Insulation

Continuous Insulation iso

Cladding (Brick Veneer Shown)

Gypsum Wallboard (Interior side) - OR - Cladding (Exterior Side)

Light frame and mass wall systems with continuous insulation (ci) for code-compliant residential and commercial building construction.

In American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) 90.1-2010, Energy Standard for Buildings Except Low-rise Residential Buildings, the ci concept is defined as: insulation that is continuous across all structural members without thermal bridges other than fasteners and service openings. It is installed on the interior, exterior, or is integral to any opaque surface of the building envelope. This approach is not new to insulation—it has been commonly employed for many years on various types of low-slope roofing systems. However, use of truly continuous insulation within building walls has lagged behind its energy-saving potential. The situation is changing through the emphasis of higher-performing wall assemblies. This article focuses on the application of ci to building walls. Like any construction material, ci must be properly specified to ensure its intended performance and appropriate use. In this regard, this article addresses five topics to consider when specifying ci for walls: • function and versatility; • materials; • modern energy code requirements; • building code requirements; and • construction detailing.

Function and versatility As shown in Figure 1, ci can be used with various wall structural systems and cladding materials, such as:

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Figure 2 CONTINUOUS INSULATION MATERIAL TYPE

RVALUE PER INCH OF THICKNESS

Fibreglass blown into wall

3.2

EPS (ASTM C578, Type II)

4.0

XPS (ASTM C578, Type X)

5.0

Polyiso (ASTM C1289, Type I)

6.0*

Examples of minimum R-value per inch for common types of continuous insulation (foam sheathing). Refer to manufacturer data for specific R-values.

• cement board; • portland cement stucco; • wood lap; • brick veneer; • stone; and • vinyl siding. In all these applications, its primary function is to provide code-compliant or better energy conservation performance. Additionally, properly qualified and installed ci products can serve other important functions for exterior wall assemblies, including air barriers and water-resistive barriers (WRBs). When laminated to structural materials, ci can even provide structural functions such as wall bracing. It is important to refer to the insulation manufacturer’s data for code-approved capabilities.

Polyiso and continuous insulation Various foam plastic insulating sheathing materials and other types of products are available to address ci applications on walls. The most common foam plastic insulating sheathing materials include expanded polystyrene (EPS), extruded polystyrene (XPS), and polyisocyanurate (polyiso) foam. Each product type has different thermal properties (affecting the required thickness), costs, and capabilities, as shown in Figure 2.1 Regarding polyiso, it is a closed-cell, rigid foam board insulation used primarily on the roofs and walls of offices, healthcare facilities, warehouses, retail, and industrial manufacturing facilities and educational institutions. One of North America’s most widely-used and cost-effective insulation products, it offers excellent fire performance. As roof insulation, it meets Factory Mutual (FM) 4450, Approval Standard for Class 1 Insulated Steel Roof Decks, and Underwriters Laboratories (UL) 1256, Fire Test of Roof Deck Constructions. As a wall component, it meets ASTM E84, Standard Test Method for Surface Burning Characteristics of Building Materials. As Figure 2 illustrates, polyisocyanurate continuous insulation has at least a 20 to 80 per cent greater R-value per inch than other common types of continuous insulation. When compared to fibreglass insulation blown into walls, polyiso’s R-value is 87 per cent higher and when compared to XPS, polyiso’s thermal performance is 20 per cent higher. This means more energy savings and/or more manageable wall thicknesses.

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With thinner, energy-efficient walls using polyiso continuous insulation, there will be more usable floor area within the footprint of the building. Also, cladding materials are more easily installed.

Modern energy code requirements Continuous insulation provides one of the most thermally efficient ways of complying with modern energy codes. It mitigates avoidable heat loss due to thermal bridging in walls that are not continuously insulated. Building codes require structures to meet certain R-values to achieve a specific level of efficiency. The climate zone plays a big role in determining what the minimum R-value has to be for a specific region. According to ASHRAE 90.1’s Table B1-2, Canada is in Climate Zones 6, 7, and 8, with some example solutions using continuous insulation illustrated in Figure 3 (page 10). The country’s National Energy Code for Buildings (NECB) defines climate zones differently in increments of 1000 heating degree days (18 C [64 F] basis). For these and other reasons, solutions may vary for a given project location depending on the climate zone and which code is used.

Building code requirements When using continuous insulation to meet or exceed the applicable energy code, other matters of building code compliance should also be considered.

Water-resistive barrier Many ci products can be used as a WRB behind cladding—providing water resistance and thermal performance in one product. It is important to refer to the manufacturer’s installation instructions and code-compliance data. Alternatively, water-resistive barriers can be separately applied to walls with ci.

Wind pressure resistance For code compliance guidance on wind pressure resistance of foam sheathing materials, one should refer to the manufacturer’s installation instructions and design data. In some applications, wind pressure resistance is only a matter of temporary construction concern because the product is encompassed or restrained by other materials designed to resist wind pressure. In other cases, the foam sheathing material may be required to resist wind loads. For example, in their 2015 editions, the U.S. model building codes now reference American National Standards Institute/Structural Building Components Association (ANSI/SBCA) FS 100, Standard Requirements for Wind Pressure Resistance of Foam Plastic Insulating Sheathing.2 Depending on the foam sheathing type and thickness used, its wind pressure capability may actually exceed the capacity of the supporting framing.3 Thus, wind pressure resistance is a matter that must apply to all components in any given wall assembly for a complete solution.

Cladding (siding) attachment Various proprietary and standard fasteners and connection strategies can be used for attachment and support of cladding materials when installed over ci. Several standardized

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Figure 3

ASHRAE 90.1 2010  RESIDENTIAL CLIMATE ZONE

Cavity Insulation

Continuous insulation

Zone 6 (2 x 4 walls)

7.5

Zone 7 (2 x 4 walls)

7.5

Zone 8 (2 x 4 walls)

15.6

Continuous insulation minimizes thermal bridging and provides economic and performance benefits over use of cavity insulation in exterior walls.

solutions for gattaching siding and furring over foam sheathing up to 102 mm (4 in.) thick have been added to the 2015 editions of the U.S. model building codes. The design professional and cladding installer should consult the cladding manufacturer’s installation requirements to co-ordinate requirements. For example, minimum siding fastener size and penetration into framing should be maintained; longer fasteners may be required.

Fire performance Foam plastics are held to a comprehensive set of fire-performance requirements that, in some cases, exceed those applied to other common construction materials. The requirements include various types of fire tests and criteria to address flame spread, smoke development, and ignition protection. Foamed plastics used as part of a non-load bearing exterior wall must comply with the full scale fire test UL Canada (CAN/ULC) S134, Standard Method of Fire Test of Exterior Wall Assemblies. Load-bearing walls using foam plastics must comply with CAN/ULC S102, Standard Method of Test for Surface Burning Characteristics of Building Materials and Assemblies.

Moisture vapour retarders It is important to ensure ci is specified with moisture vapour retarders in such a way vapour is properly managed. Diffusion is managed by control of vapour permeance and surface temperatures of the material layers comprising an assembly. For example, the National Building Code of Canada (NBC) has provisions in Part 9, Section 9.25.5 addressing the use of low-perm materials on the exterior side of a wall assembly by providing insulation ratios to control surface temperatures in combination with the use of a Class I (vapour-impermeable) or Class II (vapour-semi-impermeable) interior vapour retarder. As with any building assembly, a hygrothermal analysis may be performed to justify alternative designs and address special conditions for moisture vapour control. For example, a design using a ‘smart vapour retarder’ may provide an appropriate level

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Polyiso continuous insulation can enable thinner, more energy-efficient walls— this creates more usable floor area within the footprint of the building.

of moisture diffusion control while also improving drying potential. Finally, adequate control over indoor relative humidity (RH) and minimization of air-leakage by use of a continuous air barrier system is important to a completely integrated and successful approach to moisture vapour control for any wall assembly.

Construction detailing It is important to provide workable and complete construction details for walls with ci to ensure a constructible and functional assembly relating to many of the previously discussed topics. Construction details to consider include: • envelope component attachments; • integration of flashing and WRB; • integration of furring (if used) around wall penetrations and flashing; • attachment of cladding to wall framing through ci or to furring; • details for cladding attachments through ci at inside and outside corners; and • installation detailing per NFPA 285 tested assembly when required. Various useful detailing concepts can be found from various sources online.4 For proprietary cladding or exterior wallcovering systems that include continuous insulation, the specific manufacturer’s installation details and instructions should be consulted.5

Notes 1

For additional information on polyisocyanurate, visit www.pima.org—the site of the Polyiso Insulation Manufacturers Association. For the other materials mentioned, industry association websites offer a variety of technical resources. Visit www.xpsa.com, www.epsmolders.org, and www.foamsheathing.org. 2 For more info, visit www.sbcindustry.com/sbca-standards-development. 3 Visit apps1.eere.energy.gov/buildings/publications/pdfs/building_america/highr_walls_ wind_pressure_test_.pdf. 4 For example, visit www.drjengineering.org/products/foam-sheathing. 5 For more information on the advantages of continuous insulation over other noncontinuous insulation wall sheathing choices, visit polyiso.org.

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Part Two Specifying Reflective Insulation

BY DAVID W. YARBROUGH, PHD, PE

David W. Yarbrough, PhD, PE,is vice-president of R&D Services, an independent lab specializing in thermal insulations. He is also an emeritus professor of chemical engineering at Tennessee Technological University. A collaborator with the Reflective Insulation Manufacturers Association (RIMA International), Yarbrough is a member of the Building Enclosure Technology and Environment Council (BETEC) Board of Directors, ASTM Committee C16, and ASHRAE. He can be reached at dave@rdservices.com.

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Images courtesy RIMA International

Specifying Reflective Insulation Building envelope and equipment applications The effective specification and installation of all types of thermal insulation requires an understanding of the factors affecting performance. The specification of a thermal resistance (RSI or R-value) alone does not ensure the intended heat-flow reduction. In virtually all cases, space for insulation must be provided and insulation material must be installed to conform with the manufacturersâ&#x20AC;&#x2122; requirements. In the case of reflective insulations, factors such as heat-flow direction, air-space dimensions, and location in the building envelope should be considered.1

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Figure 1 RSI for 20-mm Air Gap 1.00

RSI

0.80 0.60

Down

0.40

Horizontal Up

0.20 0.00 -40

-20

Mean Temperature (C)

RSI for 40-mm Air Gap 2.00

RSI

1.50 1.50

Down

1.00

Horizontal Up

0.50 0.00 -40

-20

Mean Temperature (C)

The upper-most table shows the calculated RSI for 20-mm (4â &#x201E;5-in.) air gaps. The bottom shows the calculated RSI for 40-mm (1 3â &#x201E;5-in.) gaps.

The specification of conditioning equipment and reliable prediction of utility use requires understanding of the variation of the performance of any selected insulation with, for example, temperature, air movement, and thickness. In addition, the thermal performance of enclosed reflective air spaces (reflective insulations) depends on heatflow direction, placement of low-emittance surfaces, and temperature differences. This article discusses factors to be considered in the specification of reflective insulation systems. In the United States, the labelling and specification of reflective insulations for use in the building envelope or to insulate equipment is set out in ASTM C1224, Standard Specification for Reflective Insulation for Building Applications. However, Canada has not yet published a standard or guide for the evaluation of reflective insulation products.

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Product Types and Applications Product type

Typical applications

Single sheet

• wall cavity to form one or more reflective air spaces • bottom edge or side of rafter to form an enclosed reflective air space below the roof deck • bottom edge of floor joists to form a reflective air space • between floor joists to form a reflective air space • between and below floor joists to form two reflective air spaces • reflective house wrap

Single-layer bubblepack

• wall cavity to form one or more reflective air spaces • bottom edge or side of rafter to form an enclosed reflective air space below the roof deck • reflective duct insulation • water heater wrap • reflective house wrap

Double-layer bubblepack

• same applications as single bubblepack

Faced polyethylene foam

• foil or film faced and used in same applications as bubblepack

Multilayer insulation

• installed in wall cavities, between floor joists, between rafters in attics, between rafters in cathedral ceiling • masonry wall insulation

Reflective panels (sheathing)

• form enclosed reflective air space with low emittance on one side

Faced rigid foam board

• low-emittance foil or film with adjacent enclosed air space

Faced wood panels

• low-emittance foil of film with adjacent enclosed air space

Therefore, the development of a specification for a specific project should take into account both the intended location and the space available for the reflective insulation assembly. It should also examine several other criteria in order to parallel the ASTM standard. Such aspects include: • location, dimensions, and heat-flow direction for the space to be insulated; • RSI m2·K/W (R-value) for the installed reflective insulation assembly (assembly value includes the RSI for the material); • emittance of the surface(s) of the particular reflective insulation material; • resistance to humidity should be represented by test results showing emittance is not significantly increased by exposure to high humidity; • surface burning characteristics, along with flame-spread and smoke-development indices; water vapour transmission (i.e. permeance): given both water vapour retarders • and water vapour-transmitting (i.e. perforated) products are available, selection depends on local regulations and building enclosure design; • installation instructions for building or equipment applications; and • resistance to fungal growth, absence of bleeding and delamination, and satisfactory pliability are elements of ASTM C1224—a laboratory test report should show satisfactory performance is achieved.

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Basis for performance Thermal radiation across air spaces is an important part of the overall heat transfer across the building envelope in all climates. This thermal radiation is proportional to the effective emittance (E), which depends on the emittances of the hot and cold surfaces enclosing the region, as shown: E = 1/(1/εcold + 1/εhot – 1) (1) In other words, the effective emittance for an enclosed air space depends on the emittance of both the insulation and the surface it faces. ‘Effective emittance’ describes the performance that results from two parallel surfaces bounding an enclosed reflective air space. It does not depend on the direction of heat flow. The locations for emittances, hot and cold, can be reversed without changing the value of E. This means a low-emittance surface performs the same when installed on either the cold or warm side of an enclosed air space. Reflective insulation products use low-emittance surfaces to suppress thermal radiation, providing thermal resistance. They differ from many other insulations in that the thermal resistance is based on an assembly consisting of both the product itself and the adjacent enclosed air spaces. (Reflective insulation materials installed in the building envelope result in reflective insulation assemblies.) Thermal emittance is a number between zero and one. Reflective products have at least one surface with an emittance near zero and facing an enclosed (unvented) air space. Metals with smooth polished surfaces generally have emittance less than 0.1, while most building materials like wood and masonry are around 0.9. Aluminum foils and metalized films have been the materials of choice for the exterior surfaces of the reflective insulation (i.e. facers) because of their low emittance, low cost, corrosion resistance, and favourable mechanical properties. Aluminum in the form of thin foils or metalized films laminated to a substrate such as paper, wood, or plastic are used to produce reflective insulations. The thermal emittance value (total hemispherical emittance), consequently, is a very important specification requirement for any reflective insulations—it is generally in the 0.03 to 0.06 range. The following equations are often used to estimate the thermal resistance (RSI) for an enclosed reflective air space that is part of the building envelope. RSI = ΔT / (Q rad + Q convection-conduction) Qrad = E · σ · ([Thot + 273.15]4 – [Tcold + 273.15]4) where σ = 5.67 · 10-8 W/(m2·K4) and T is in degrees C. This equation is also one of many expressions used to calculate the convective contribution to the total heat flow: Qconvection-conduction = Nu · ( λ air · ΔT /L) RSI for enclosed reflective air spaces can be measured using a hot-box facility, which is a large-scale apparatus for measuring the heat flow across a building element such

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as a section of wall. It must be operated in accordance with ASTM C1224 or reliably estimated using engineering correlations2 or computer simulations.3

Products Reflective insulations include single-sheet products that consist of low-emittance foils or films bonded to a substrate such as paper, plastic, or polyethylene bubblepack and multiple-layer insulations. (See “Product Types and Applications, page 15.”) In most cases, both sides of the single-sheet insulation are faced with low-emittance foil or film. When only one side has a low-emittance surface, it is important to install that facing the enclosed air space. Reflective insulations with low-emittance surfaces on both sides are commonly used to create two enclosed reflective air spaces in series. The reflective insulation products with multiple layers are installed to form two or more enclosed reflective air spaces. The specified number of layers and the spacing must be present for the expected thermal resistance to be achieved. Polyethylene bubblepack faced with low emittance foil or film is generally available in two thicknesses: ‘single’ bubble products nominally 6 mm (¼ in.) thick and ‘double’ bubble products 12 mm (½ in.) thick. The applications for the two are the same, but the double-bubble insulation has a greater material R-value and tear strength. Most reflective insulation products can also be used as ‘radiant barriers’—a term employed for ventilated spaces or large air spaces like a residential attic. The distinction between reflective insulations and radiant barriers results from the way the material is used. Reflective insulations are enclosed reflective air spaces (i.e. nonventilated) while radiant barriers involve ventilated air spaces. Enclosed reflective air spaces are labelled with RSI-values that have the same units and same meaning as other building insulations; radiant barriers are not labelled with an RSI-value. The thermal performance of reflective assemblies varies with temperature, as is the case with all insulations. R-values for thermal insulation materials typically decrease as the temperature increases. Products are labelled at a particular temperature— for example, 24 C (75 F)—so comparisons of competing products can be made on a uniform basis. The thermal performance also varies with temperature difference since gravity-driven convection is a factor. The convective component increases as temperature difference across an enclosed reflective cavity increases. The thermal resistance has a strong dependence of heat-flow direction, thus requiring the intended use or location of the reflective insulation be known before RSI values can be assigned. This is because the temperature of the enclosed air space and the temperature difference across it depend on the location in the envelope. The temperature difference across an enclosed air space depends on the overall design of the building envelope where the reflective insulation is to be used. The air-gap temperature difference is a fraction of the total air-to-air temperature difference at the location in question. ΔTair gap = ΔTtotal · RSI air gap / RSI total RSI air gap = ΔTair gap · RSI total / ΔT total

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Figure 2 Exterior Cladding or Stucco

A Exterior OSB Sheathing

Unfaced 89 mm Fiberglass Batt

140 mm Studs 0.41 or 0.61 mm OC

Interior Drywall

Multi-Layer reflective insulation

Hybrid application using fibreglass insulation and a reflective insulation assembly in a woodframed wall.

Exterior Cladding or Stucco

Images courtesy Fi-Foil Company

Exterior OSB Sheathing

Spray 1PMZVSFUIBOF 'PBN

89 mm Studs 0.41 or 0.61 OC

Interior Drywall

Multi-Layer reflective insulation

Hybrid application using sprayed polyurethane foam (SPF) insulation and a reflective insulation assembly in a wood-framed wall.

A solution for ΔTair gap or RSI air gap involves an iterative procedure since RSI total includes RSI air gap and ΔT total includes ΔTair gap.4 The performance of the enclosed reflective air space is best when the ratio RSI air gap / RSI total is small. This is often the case when an enclosed reflective air space is part of a hybrid insulation assembly. The variation in thermal resistance (RSI in W/m2·K) is shown in Figure 1 (page 14) for mean temperatures from −26 to 94 C (about −15 to 200 F) and air gaps of 20 and 40 mm (4⁄5 and 1 3⁄5 in.) in a wall, ceiling, or floor assembly. The RSIs were calculated using the procedure described in ASTM Special Technical Publication (STP) 1116, Insulation Materials: Testing and Applications, using a 10-C (18-F) temperature difference across the air gap. The RSI-value in Figure 2 demonstrates the reflective assemblies perform as well or better at low temperatures than they do at high temperatures. The significant difference in RSI with changes in heat-flow direction is shown in the figure. The differences in RSI

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Figure 4

Photo courtesy Reflectix

Photo courtesy Covertech Fabricating

Figure 3

Fibreglass-reflective insulation hybrid.

Reflective duct installation.

with heat-flow direction is due to the convective component largely absent in the heat-flow down direction. There is significant increase in RSI with thickness in the heat-flow down direction because the heat transport is primarily conduction. There is not a significant increase in RSI with thickness increase from 20 to 40 mm when radiation is the dominant heat-transfer mechanism. This type of performance differs from fibrous or cellular plastic insulation where convection is not usually present.

Hybrid insulation assemblies Reflective insulations are used with other insulations like fibreglass or sprayed polyurethane foam (SPF) to form hybrid insulation assemblies. The hybrid assemblyâ&#x20AC;&#x2122;s thermal resistance is the sum of the individual RSI-values. The use of enclosed reflective air spaces in this case is attractive because uninsulated space is able to be ungraded to an enclosed reflective air space. Additionally, the temperature difference across the reflective air space is generally minimal, which makes the convective component of the heat transfer small or absent. This is an optimal situation for a reflective insulation assembly. Figure 2a (page 18) shows a hybrid system that combines fibreglass insulation and a reflective insulation. Figure 2b (page 18) is a hybrid system using sprayfoam as one component. In both cases, the total thermal resistance in the cavity is the sum of the fibrous or foam insulation and the reflective insulation assembly. A specification should identify the total thermal resistance to be provided by the hybrid assembly. For this type of system, the overall thermal resistance should be stated along with the RSI-value to be provided by the fibreglass or spray-foam insulation. The space allocated to the reflective components should also be specified. If the reflective insulation assembly is intended to be water vapour transmitting or a water vapour barrier, then the type should be specified. Figure 3 shows a fibreglass-reflective hybrid. The fibreglass has been compressed to provide space for inset stapling of the reflective insulation. This type of assembly can

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also be constructed using furring strips as spacers. The photograph shows only two cavities with reflective insulation installed.

Reflective duct insulation Reflective insulation can be installed on air-handling equipment (i.e. ducts) with and without spacers—material to maintain an enclosed air space between the duct surface and the insulation material wrapped around. Figure 4 (page 19), shows an example of a reflective duct installation that includes radial spacers and two reflective air spaces. The thermal resistance of this type of product is determined in accordance with ASTM C1668, Standard Specification for Externally Applied Reflective Insulation Systems on Rigid Duct in Heating, Ventilation, and Air Conditioning, for an assembly specified by the manufacturer. The specification of this type of insulation should include the requirement for spacers (when appropriate), the distance across the air gaps, and the thermal resistance.

Specialty applications Reflective insulation assemblies for water heaters and garage doors have been available for many years. The thermal resistance intended for the application should be specified along with a requirement for detailed installation instructions. The thermal performance includes a contribution from the air space between the surface of the door and the reflective insulation. The assembly should be specified in terms of number of layers and spacing that will provide the label RSI-value.

Conclusion Enclosed reflective air spaces provide resistance to heat flow by significant reduction in radiation across air spaces due to presence of low-emittance surfaces. In many cases, there will be air movement (convection) inside the enclosed air space. The convective component of the total heat gain or loss varies with heat-flow direction being the least when the heat-flow direction is downward and temperature difference that is usually small in the case of hybrid systems. Like all thermal insulations, the thermal performance of enclosed reflective air spaces is characterized by an R-value. The use of reflective insulation as part of a hybrid system provides a way to optimize the use of the available space for insulation in cold climates. For more information on reflective insulation, design/construction professionals can contact the Reflective Insulation Manufacturers Association (RIMA International).

Notes 1

This author acknowledges Wesley Hall (Reflectix) for reviewing the article. For more, see ASTM Special Technical Publication (STP) 1116, Insulation Materials: Testing and Applications, by this author and A.O. Desjarlais. Also, see International Organization for Standardization (ISO) 6946, Building Components and Building Elements—Thermal Resistance and Thermal Transmittance: Calculation Method. 3 See the article, “Investigation of Thermal Performance of Reflective Insulations for Different Applications,” by Hamed H. Saber, which appeared in volume 52 of Building and Environment (Elsevier, 2012). 4 See ASTM STP 1116. 2

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Part Three Insulationâ&#x20AC;&#x2122;s Role in Controlling Noise

BY STACY FITZGERALD-REDD

Stacy Fitzgerald-Redd is the communications director for the North American Insulation Manufacturers Association (NAIMA), an industry source for energy efficiency, sustainable performance, and the application and safety of fibreglass, rock wool, and slag wool insulations. She has more than 20 years of association management and communications experience. Fitzgerald-Redd may be contacted at sfitzgerald-redd@naima.org.

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Photos courtesy CertainTeed Corporation

Insulation’s Role in

Controlling Noise Acoustical management is a challenge for both design professionals and building occupants. A certain level of background sound within a building is expected, and generally contributes to a pleasant ambient environment. Unwanted noise can cause occupants to feel irritable, distracted, anxious, hostile, or annoyed. This is why it is critical to closely review the intended use and design of commercial environments so sound levels do not become ‘noise’ concerns.

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For example, within a factory work environment, anything beyond 85 decibels (dB) over an eight-hour time period is considered hazardous and can lead to hearing loss, according to the U.S. Centers for Disease Control and Prevention (CDC).1 Construction practices to reduce noise are increasingly important, with many builders and architects looking for cost-effective ways to further reduce sound transmission. When properly installed within a wall, ceiling, or floor assembly, fibreglass, rock, and slag wool insulation offers sound-absorbing benefits and reduce unwanted noise in occupied spaces.

Where to begin Building environments can be affected by multiple, noise competing sources both inside and outside. For the first category, examples include traffic, lawn and garden equipment; indoor sources include appliances and electronics. The result impedes communication and makes focusing and communicating more difficult. In extreme cases, noisy environments can contribute to hearing loss. At the start of a building project, architects and designers consider use of the space and potential noise sources, planning possible acoustical solutions for the project, particularly when there is a special-use room (e.g. a sound studio or media room within the building). An acoustical engineer can advise of the proper solutions to address any potential problems with noise within a space. In problem areas, this is best addressed at the onset of a project. While it is possible to retrofit noise attenuation products after installation of building equipment, costs are generally much higherâ&#x20AC;&#x201D;and the results are about half as effectiveâ&#x20AC;&#x201D;as designing proper sound control into the system before the noise source is installed.

Acoustical insulation applications Fibreglass and rock and slag wool insulations can help absorb sound travelling through wall and floor assemblies. The acoustic enhancement insulation can be installed in roof/ceiling applications, as well as interior or exterior wall applications in wood or metal framing cavities for acoustic enhancement. Additionally, acoustic insulation panels that are installed over hard surfaces help reduce echo and improve sound clarity in gymnasiums, conference rooms, and concert halls. These installations are manufactured to common stud widths and are slightly wider than common stud spacing to accommodate easy friction-frit installations and prevent sagging.

The basics of sound Sound is energy travelling in waves that have both amplitude and frequency. Amplitude relates to pressure and, to a large degree, affects loudness. Frequency relates to pitch and affects how high or low a sound is. It is the intensity of sound (i.e. dB) with which most people are familiar. A typical conversation in a normal speaking voice measures about 60 dB and a power mower is approximately 107 dB. Sound waves can travel through air, water, wood, masonry, or metal. Depending on how it travels, sound is airborne or structure-borne. In the first case, it flows from the source directly through the air. Structure-borne sound, on the other hand, travels through solid materials, usually in direct mechanical contact with the sound source,

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In office spaces without adequate insulation, it is not uncommon for productivity to drop when employees can hear nearby conversations.

or from an impact on that material. For example, loud speakers on a floor vibrate this sound that then becomes airborne, enabling people to hear it. Dedicated noise-control solutions should address both airborne and structure-borne sound by: • replacing the sound source with a quieter one; • blocking the sound or breaking the vibration path; or • absorbing the sound with a light, porous material that soaks up sound waves. The degree to which construction is effective at blocking noise is expressed as its sound transmission loss (STL) value. These values are measured at each one-third octave band frequency from 125 to 4000 Hz, and are expressed in dBs. STL values are determined and measured in accordance with ASTM E90, Standard Test for Laboratory Measure of Airborne Sound Transmission Loss of Building Partitions and Elements. From the sound transmission loss values, a single-number rating called the sound transmission class (STC) is determined using ASTM E413, Classification for Rating Sound Insulation. Every newly built dwelling unit in Canada must be separated from other adjacent units in a building by a separation wall, floor, or ceiling partition constructed to provide an STC rating of at least 50, according to the National Building Code of Canada (NBC).

Constructing walls to control noise Sound transmission loss from one side of a wall to the other depends on a number of design properties including the materials used and the properties of sound. Doublewall assemblies effectively ‘break,’ or decouple, the vibration path within the wall

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Photo courtesy Owens Corning

Acoustical batt insulation being installed in a wall.

assembly. As a result, most double-wall assemblies provide higher STC ratings compared to single-layer walls. The STC values of a lightweight wall can be increased as much as six to 10 STC points by adding acoustical insulation to the stud cavity. Any gaps within the structure should be sealed as any structure that leaks air also leaks sound. In a multi-storey building, controlling sound transmission through ceilings/floors is an important step to optimize occupant comfort. In addition to the STC rating, floor/ ceiling assemblies can be assigned an impact insulation class (IIC) rating based on how well they perform at reducing structure-borne sound that comes from footsteps or dropped objects as examples. Adding fibreglass or rock and slag wool insulation to the joist cavity, along with a resilient ceiling structure below the joists, will increase the STC and IIC ratings of a floor/ceiling construction assembly.

Noise control tips When addressing a noise control problem, the first step is to investigate the source of the noise to determine whether there is a simple solution to resolving the problem. A particular noisy piece of equipment, for example, might need a simple adjustment or repair to eliminate or reduce the noise. If this is not the case, the next step is to measure the noise at its source, along its path and at the receiver or listenerâ&#x20AC;&#x2122;s location.

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Finally, once the noise source has been located, diagnosed, and measured, a solution can be designed. The noise reduction strategy may involve an acoustic treatment at more than one location. For example, an acoustical enclosure of the noise source plus soundabsorbing materials along the path may be the most effective and economical solution to address the problem. Additionally, finding a solution to the noise control problem may involve a treatment that provides both sound absorption and sound transmission loss properties. Walls, ceilings, and floors are key focal points for addressing noise problems, but there are other sound control measures that can significantly reduce unwanted noise in buildings including: • insulating heating and air-conditioning ducts with fibreglass-lined sheet metal ducts; • using double or triple-pane windows; • adding solid doors in between rooms; or • caulking around electrical boxes and underneath wall plates. An added benefit of these measures is they also help increase the building’s energy efficiency because air leaks throughout the building cause the HVAC system to work harder to heat and cool the building.

Proposed changes to Canada’s National Building Code The current standard for measuring the airborne sound transmission, International Organization for Standardization (ISO) 15712.1, Airborne Sound and Insulation Between Rooms, developed by the European Commission for Normalization, provides a reliable estimate for some types of construction. However, it does not really apply for the lightweight wood-framed construction commonly used for Canadian low-rise and mid-rise buildings. For lightweight framed construction, the Apparent Sound Transmission Class (ASTC) method developed by ASTM is more suitable for measuring multiple paths for sound transmission between adjacent rooms, because it considers not just direct transmission through the separating assembly but also indirect transmission (i.e. flanking) where sound passes over the top, or under the primary partition separating two spaces through paths such as ceilings, walls, and floor surfaces. A steering committee comprising Canadian building industry professionals has developed recommendations for improving acoustics in Canadian buildings. The recommendations, which are included in the 2015 NBC, are a shift from a focus of individual assemblies (i.e. walls or floors) to a focus on complete system performance, including direct and indirect south paths. Standardized procedures for calculating the overall transmission, combined with standardized measurements to characterize subassemblies, provide a much better prediction of sound transmission between adjacent indoor spaces. ISO 15712.1 uses laboratory test data for sub-assemblies such as walls and floors as inputs for a detailed procedure to calculate the expected sound transmission between adjacent rooms in a building. This standard works well for some types of construction, but there are two obstacles to using it in North America: • incompatibility with the ASTM standards used by the Canadian construction industry; and

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Photo courtesy Roxul

The insulated boards used in these theatre panels are covered in bass-trap acoustic-energy-absorbers.

â&#x20AC;˘ low accuracy of its predictions for lightweight wood or steel frame construction. To bypass the limitations of ISO 15712.1, the recommendations seek to merge ASTM and ISO test data in the ISO calculation procedure, and provide guidance for applying extended measurement and calculation procedures for specific, common types of construction. One can show compliance to the current minimum STC requirement in the NBC using results from measurements carried out in accordance with ASTM E90, Laboratory Measurements of Airborne Sound Transmission Loss of Building Partitions and Elements, or by conducting onsite measurements using ASTM E336, Measurements of Airborne Sound Transmission Sound Attenuation between Rooms in Buildings, or referencing assemblies cited in Appendix A, Table A-9.10.3.1 (wall assemblies) or table A-9.10.3.1.B (floors). Better methods to measure sound will facilitate enhanced acoustic performance for insulation in multi-unit structures.

Conclusion The best strategy for optimizing acoustic comfort in dwelling units is to address all the possible sound transmission paths in the architectural details so they can be easily incorporated during construction. Identifying the location of noisy equipment, incorporating a systems approach that allows consideration of all noise paths, sealing all air leaks within the building, and considering all the sound transmission paths will help avoid potential noise control problems within the building space and costly repairs.

Notes 1

For more information, visit www.cdc.gov/niosh/topics/noisecontrol.

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Part Four The Effect of Temperature on Insulation Performance

BY CHRISTOPHER SCHUMACHER, M.A.SC.

Christopher Schumacher, M.A.Sc., is a principal with RDH Building Science Laboratories, a consulting firm specializing in design facilitation, enclosure commissioning, forensic investigation, and training and communications. His presentations on temperaturedependent R-values include the Westford Building Science Symposium in 2011 and the Rock-toberfest Rockwool Symposium in 2014. He has also written on this topic for buildingscience.com.

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Images courtesy RDH Building Science Laboratories

The Effect of Temperature on Insulation Performance On the surface, R-value is a simple thing. In fact, it has become the standard metric of thermal performance precisely because it is easy to explain and understand. Most insulation materials have ‘label R-values’ stamped on their faces (or at least displayed in large print on the packaging), but these values do not tell the whole story of how insulation performs in service. Some complicating factors—such as thermal bridging—have become fairly well-known. However, in order to meet current needs for energy-efficient, durable, comfortable, and cost-effective buildings, it is critical to continuously improve the industry’s understanding and handling of insulated assemblies.

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Figure 1

Heat flow meter used to measure thermal conductivity and resistance per ASTM C518, Standard Test Method for Steady-state Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus.

R-value is a measure of thermal resistance for materials. In other words, it denotes how much heat is prevented from flowing through a layer of material at a given thickness. In North America, R-value is most commonly given in imperial units, where one R = 1 (sfÂˇFÂˇhr)/Btu, and a 50-mm (2-in.) thick layer of insulation might be R-10. In Canada, RSI units are also used; one RSI = 1 (m2ÂˇK)/W and RSI = R / 5.678, meaning the 50-mm thick layer of insulation would be RSI-1.76. Regardless of the units used, the effectiveness of thermal resistance depends on a number of factors. For example, temperature-dependent R-value is a phenomenon relatively unknown outside of the world of researchers and academics. Temperature dependency refers to changes in the R-value of insulation over a range of temperatures. For example, a 25-mm (1-in.) thick board of extruded polystyrene insulation (XPS) might have a label R-value of RSI-0.88 (R-5), but its actual performance may be closer to RSI-0.97 (R-5.5) under cold-climate winter conditions, or as low as RSI-0.72 (R-4.1) under hot-climate summer conditions. The label R-value is not incorrect; it refers to performance under a specific set of standard test conditions and does not necessarily reflect how a material performs on a building. Temperature dependency matters because the insulation in real-world buildings often experiences temperatures differing significantly from standard test conditions. In fact, the standard test condition temperatures are almost never seen in a typical building. Research has characterized how R-values change with temperature by measuring materials at different mean temperatures and using various temperature ranges.

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Figure 2

The above tables provide a comparison of surface temperatures for ‘standard’ tests as per ASTM C1058, Standard Practice for Selecting Temperatures for Evaluating and Reporting Thermal Properties of Thermal Insulation, versus Building Science Laboratories’ (BSL’s) “Service Temperatures.”

This article describes an ongoing research project at RDH Building Science Laboratories that has included a variety of insulation materials over several years. In most cases, the insulation performed a little better than expected when the mean temperature was lower (simulating cold outdoor conditions), and a little worse when it was higher (simulating warm outdoor conditions). Further, the relationship between R-value and temperature is nearly linear. Where this pattern occurs, R-values are predictable and temperature can be easily accounted for. However, some unusual patterns have also been found. Polyisocyanurate (polyiso) insulation provides a useful example of how unusual temperature dependency patterns can be identified and then accounted for in modelling and design.

Determining R-values Before getting into the details of BSL’s research, it is important to understand the origins of the R-value and how it is typically measured. The R-value was proposed by Everett Shuman in the 1940s as an easy-to-compare, repeatable measure of insulation performance. Prior to that, thermal performance was expressed in terms of conductance or the ability for materials to conduct heat. Materials provide better performance when they have lower thermal conductance. Industry decision-makers felt consumers would be confused by the concept ‘smaller is better.’ When thermal performance is expressed in terms of R-value or thermal resistance, higher numbers represent better performance. The R-value went on to become the de facto metric across North America, familiar to both consumers and professionals. It has helped many designers and consumers make more energy-efficient choices, but its importance in influencing purchase decisions has also led to some unscrupulous marketing claims. In the aftermath of the 1970s oil crisis in the United States, fraudulent R-value claims became so widespread the United States Congress passed a consumer-protection law in response, the “Federal

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Figure 3

These are R-values for several common insulation materials. Measured using ‘standard’ mean temperatures of –4, 4, 24, and 43 C (25, 40, 75, and 110 F), and temperature difference of 27.8 C (50 F).

R-Value Rule” (16 Code of Federal Regulations [CFR] Part 460, “Trade Regulation Rule Concerning the Labeling and Advertising of Home Insulation”). Under this rule, claims about residential insulation must be based on specific ASTM procedures. Of these, ASTM C177, Standard Test Method for Steady-state Heat Flux Measurements and Thermal Transmission Properties by Means of the Guarded-hot-plate Apparatus, and ASTM C518, Standard Test Method for Steady-state Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus, are by far the most commonly used, as they can be quickly completed with small easy-to-handle samples—typically between 305 x 305 mm (12 x 12 in.) and 609 x 609 mm (24 x 24 in.). These test methods use an apparatus that places an air-impermeable hot and cold plate in direct contact with the test sample (Figure 1, page 30). Further, the rule requires R-value tests be conducted at a mean temperature of 24 C (75 F) and a temperature differential of 27.8 C (50 F). For reasons of technical ease, this means insulation is usually tested with the cold side at about 10 C (50 F), and the warm side at around 38 C (100 F).1 In other words, the label R-value typically only provides a metric of a material’s thermal performance under one standard test condition. Clearly, the parameters of this one test do not represent any typical combination of real indoor and outdoor temperature conditions, much less the full range of conditions insulation might experience in building applications.

Thermal performance BSL’s research into temperature-dependant R-values started out by reproducing the work of Mark Graham of the National Roofing Contractors Association (NRCA).2 The testing has since been extended to consider various insulation materials using a wider range of realistic temperature conditions.

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Figure 4

Change in R-value over time for extruded polystyrene (XPS), an insulation material that employs insulating gases. Measured using ‘standard’ mean temperatures of –4, 4, 24, and 43 C (25, 40, 75, and 110 F) and temperature difference of 27.8 C (50 F).

Approach Using ASTM C518 procedures, materials were tested at a range of hot and cold temperatures. Initial tests were done at the same setpoints used by Graham. These mean temperatures of –4, 4, 24, and 43 C (25, 40, 75, and 110 F), were per ASTM C1058, Standard Practice for Selecting Temperatures for Evaluating and Reporting Thermal Properties of Thermal Insulation (shown as the “Standard” R-value tests in Figure 2, page 31). For later tests, BSL researchers selected temperatures to reflect more realistic inservice conditions, from cold, winter air temperatures through to hot, solar-heated surface temperatures (see BSL “Service Temperature” tests in Figure 2).

Results As expected (based on the physics of heat transfer), most of the tested insulating materials exhibited nearly linear temperature dependency over the range of temperatures buildings normally see.3 Results are given in Figure 3 (page 32) for fibreglass batt, stonewool batt, high-density expanded polystyrene (EPS), XPS, and closed-cell sprayed polyurethane foam (SPF). Figure 4 shows results for nominal RSI-3.52 (R-20) XPS tested at two, four, six, and 44 months after purchase to investigate the effect of aging. For all these tests, the line’s slope shows a consistent pattern where the material is more thermally resistant at colder mean temperatures and less thermally resistant at warmer mean temperatures. As most materials follow a consistent pattern, their temperature dependency can be predicted and accommodated. Most of the time, a layer of the insulation can be measured (i.e. get R-value or conductance) at several mean temperatures and then material properties can be easily predicted (i.e. R-value/in. or conductivity). This process

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Figure 5

R-values for several polyisocyanurate (polyiso) roof insulation materials. Measured at BSL’s ‘Service Temperatures’—room side always at 22.2 C (72 F) and outdoor side set to represent cold –17.7 C (0 F), cool 2.2 C (36 F), hot 42.2 C (108 F), and solar-heated surface 62.2 C (144 F) conditions.

works with standard and in-service temperatures—it should work with almost any temperature difference. However, it is possible for materials to have an unusual pattern of temperature dependence. Graham demonstrated that polyiso insulation products (available at the time of testing) displayed a markedly non-linear pattern over numerous samples from different manufacturers. More specifically, the measured R-value was significantly lower than the label R-value for tests conducted at both warm and cold temperatures. In BSL testing, polyiso was tested more extensively to better understand this unusual pattern of temperature dependency. Figure 5 shows the measured R-value of three different polyisocyanurate products, tested in 100-mm (4-in.) thick samples—two layers of 50-mm (2-in.) thick product—at BSL’s ‘service temperatures.’ It should be noted the results in Figure 5 are only applicable to the specific thickness and temperatures tested—in this case, 100 mm (4 in.) at an indoor temperature of 22 C (72 F) and outdoor temperatures between –18 and 62 C (0 and 144 F). Researchers at BSL have since developed a draft test method to fully quantify the R-value for materials having unusual temperature dependence. The method produces a temperature-dependent R-value curve independent of thickness. Figure 6 (page 35) presents an example of such a curve for several different materials. Using this approach, the temperature-dependent R-value can be quantified once, over a range of temperatures, for a given insulation product. The results can then be extended to predict the R-value of the product at any thickness and temperature.

Understanding design implications of temperature dependency In and of itself, temperature dependency is not a reason to avoid a particular type of insulation. Polyisocyanurate insulation has been used as an example in this discussion

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Figure 6

Convergent R-values measured to capture full temperature dependence of several common insulation materials. These are measured using decreasing temperature difference measurements at 16 mean temperatures.

because it exhibits an unusual relationship between R-value and temperature, and because it is commonly used in commercial roof and residential wall assemblies. Like all insulation materials, polyiso has pros and cons. It should also be remembered all materials exhibit some temperature dependence. When temperature-dependant thermal performance is not taken into account, three problems can result: â&#x20AC;˘ increased energy consumption; â&#x20AC;˘ poor occupant comfort; and â&#x20AC;˘ reduced building durability. A useful example can be found with a large warehouse or light industrial building in a climate with hot summers. If the lighting and equipment loads are moderate, ventilation requirements are minimal, and there are few windows, then much of the cooling load will be associated with gains through the roof assembly. When the roof insulation is exposed to higher temperatures (as would be typical under a solar-heated roof surface), it delivers lower thermal performance (i.e. more heat gain) than expected based on the label R-value. This is true for all types of insulation material. At the exterior surface the R-value might be reduced by 20 per cent. However, over the thickness of the roof insulation the average reduction in R-value might only be 10 per cent since the exterior layers protect the inner layers by keeping them closer to the indoor temperature. The corresponding increase in heat flow would result in an approximate 10 per cent increase in energy consumption related to the roof assembly. Whether or not this has a significant impact on building operating costs will depend on the specific climate,

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Figure 7

Predicted temperature profile and condensing plane temperature for a typical residential wall assembly insulated with 19-mm (3⁄4-in.) polyiso exterior insulation and 89-mm (3 1⁄2-in.) mineral fibre batt insulation in the stud space—assuming label R-values.

the building construction and operation, and various other interrelated factors (e.g. thermal mass and equipment efficiency). It was stated earlier most materials exhibit a decrease in R-value for hot temperatures, and an increase in R-value for cold temperatures. It seems obvious to ask whether any unexpected increase in energy consumption during warm weather is offset by unexpected reductions in consumption during cold periods. Again, the net performance will depend on specific climate, building construction, operation, and other issues. All the relevant factors (including insulation temperature dependence) can be accounted for using appropriate computer models (e.g. EnergyPlus and WUFI-Plus).4 Even in those cases where the summer loss in performance is offset by the winter bonus, there may be other building performance considerations. Several design questions might be considered: will the brief reduction in R-value have a meaningful impact on the required HVAC system capacity? If not, does it result in interior surface temperatures that adversely affect thermal comfort? Further, temperature dependence does not always result in better performance under colder temperatures. The tested polyiso insulation materials exhibited lower than expected R-values at higher and lower temperatures. For some time, polyiso board insulation has been the most commonly used low-slope roof insulation. In these applications, it is the only insulation in the assembly—as a result, the thermal performance is less than expected during both winter and summer conditions.

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Figure 8

Predicted temperature profile and condensing plane temperature for a residential wall assembly insulated with 19-mm (3⁄4-in.) polyiso exterior insulation and 89-mm (3 1⁄2-in.) mineral fibre batt insulation in the stud space—using measured temperature-dependant R-values.

Polyisocyanurate is also increasingly being used as a continuous exterior insulation over insulated stud spaces in residential and commercial wall assemblies. In these applications, the thickness of a continuous insulation is typically specified to: • minimize the impact of thermal bridging through the framing; and • reduce the potential for air leakage condensation by controlling condensing plane temperatures.5 The former is an energy consideration while the latter is a building durability concern. For a practical illustration, a residential wall assembly with a 2x4 wood frame with RSI-2.29 (R-13) fibreglass batt insulation in the stud space and 19 mm (3⁄4 in.) of polyiso insulation on the exterior provides a nice example. Assuming the polyisocyanurate insulation is rated as RSI 1.06/25 mm (R-6/in.), without accounting for temperature dependency, if the wall is subjected to conditions of 22 C (72 F) on the indoor side and –18 C (0 F) on the outdoor side, then the temperature at the condensing plane (i.e. the inside surface of the polyisocyanurate) is predicted to be –8.5 C (17 F), as illustrated in Figure 7 (page 36). In contrast, if it is assumed the polyiso exhibits a temperature dependence similar to that shown in Figure 6, then the predicted condensing plane temperature will be –12.1 C (10 F) as illustrated in Figure 8. In this case, the temperature dependence of the material is particularly significant because the entire thickness of the insulation is on

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Figure 9

Predicted temperature profile and condensing plane temperature for a typical residential wall assembly insulated with 38-mm polyiso exterior insulation and 89-mm mineral fibre batt insulation in the stud space—using measured temperature-dependant R-values.

the assembly’s cold side. That is to say none of the temperature-sensitive insulation is protected by itself or another material. To bring the condensing plane temperature back to the values originally expected, the thickness of the polyiso exterior insulation would need to be be increased to 38 mm (11⁄2 in.), as illustrated in Figure 9. Specifying more insulation is also a good option when designing roof assemblies using polyisocyanurate. A good rule of thumb for both roofs and walls is to use NRCA’s recommendation to specify polyisocyanurate insulation by its desired thickness—not its label R-value. Ideally, the thickness would be specified on the basis of annual energy simulations and hygrothermal calculations using a measured temperature-dependant R-value like that illustrated in Figure 6 (page 37). When material-specific, temperature-dependant R-values are unavailable, designers will have to make some assumptions. For polyisocyanurate roof insulation materials, NRCA recommends using an in-service R-value of 5 per inch thickness (i.e. RSI-0.88/25 mm) for heating-dominated climates or 5.6 per inch thickness (i.e. RSI-0.99/25 mm) for cooling-dominated climates.6 Another option is to use a hybrid insulation approach. Adding a layer of lesstemperature-sensitive insulation outboard of the polyiso, protects the polyiso from extreme temperatures and gets the most value from both insulation layers. An example hybrid assembly is shown in Figure 10 (page 39).

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Figure 10

A hybrid assembly using rigid mineral fibre and polyiso insulation.

Conclusion Temperature dependence can result in assemblies that do not function as expected or intended. In the case of those materials exhibiting strong temperature dependence, the consequences could be significant. Fortunately there are solutions, and as knowledge of this phenomena increases, more solutions will no doubt be developed.

Notes 1

The actual language of the rule permits test temperature differentials of 27.8 C ± 5.6 C (50 F ± 10 F) for cold-side temperatures of 7.2 to 12.7 C (45 to 55 F) and hot-side temperatures of 35 to 40 C (95 to 105 F). 2 See Mark Graham’s “Comparing Polyiso Values,” in National Roofing Contractors Association’s (NRCA’s) Tech Today at docserver.nrca.net/technical/8020.pdf. 3 If the temperatures were extended to cryogenic temperatures on the cold end and furnace temperatures as seen in industrial applications, then the relationship would be seen to be curved. However, the part of the curve that represents normal building temperatures can be treated as linear for practical purposes. 4 It should be noted the assumed temperature-dependent R-values (i.e. in the program database) may not be correct for all materials (e.g. polyiso). More material-specific data is needed. 5 In walls with sufficient exterior insulation, the dewpoint temperature of the interior air will be below the temperature of the back of sheathing, and therefore condensation due to air leakage cannot occur within the studspace. See John Straube’s BSD 163, Controlling Cold-Weather Condensation Using Insulation. Available at buildingscience.com. 6 See Mark Graham’s “Revised R-values” in NRCA’s Tech Today, at docserver.nrca.net/ technical/9599.pdf.

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Part Five Thermal Barriers and the Protection of Foamed Plastic

BY JOHN A. DALTON

John A. Dalton is the task group chair of the ASTM E06.21 committee on serviceability and a principal member of the U.S. National Fire Protection Association (NFPA) 502, Standard for Road Tunnels, Bridges, and Other Limited Access Highways. The technical service manager for W.R. Grace & Co.â&#x20AC;&#x2122;s fire protection products division, he has degrees in mathematics and industrial chemistry. Dalton can be reached at john.a.dalton@grace.com.

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Photo courtesy W. R. Grace & Co.

Thermal Barriers

and the Protection of Foamed Plastic In Canada, products approved for use as a thermal barrier for foamed plastic must pass either CAN4-S124-M, Standard Method of Test for the Evaluation of Protective Coverings for Foamed Plastics, or CAN/ULC-S101, Standard Methods of Fire Endurance Tests of Building Construction and Materials, to comply with the National Building Code of Canada (NBC).

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Images courtesy Canadian Urethane Foam Contractors Association (CUFCA)

Figure 1

The assembly for CAN/ULC S124, Standard Method of Test for the Evaluation of Protective Coverings for Foamed Plastics, for thermal barrier material over sprayed polyurethane foam.

In the Canadian market, many products—typically fibre-based or cementitious materials—can meet these requirements. Unfortunately, there has been a growing trend amongst some suppliers of ‘paintable’ ignition barriers claiming their products meet the performance of a thermal barrier without actually passing either CAN4S124-M or CAN/ULC-S101. This article provides the background on the qualities of acceptable solutions as a thermal barrier in accordance to the NBC, and discusses the current activities in the marketplace and the potential liability to the design/construction team and authority having jurisdiction (AHJ).

NBC test criteria for protecting foamed plastics Sprayed polyurethane foam (SPF) insulation is combustible and may ignite when exposed to heat or fire. During the event of a fire, smoke and combustible gases can accumulate in interior, confined spaces and lead to a deadly flashover.1 These characteristics of foamed plastics are recognized within the NBC, which details the steps to be taken to protect building inhabitants from the effects of the materials’ burning. The code specifically defines certain materials to be used as “thermal barriers” for foamed plastic insulation. These include gypsum board thicker than 12.7 mm (1/2 in.), concrete, and masonry. For other materials (that are not specifically identified), NBC stipulates testing/performance requirements to determine whether the material may be used as a thermal barrier. It splits this approval process into three categories based upon the flame spread rating of the foamed plastic insulation and details of the proposed building. Each category has its own testing requirements and pass/fail criteria. As mentioned, the NBC includes testing thermal barriers according to CAN4-S124-M and/or CAN/ULC-S101—both standards use the same time-versus-temperature fire curve, but differ in the required sample size, orientation to the fire, number and location of thermocouples, and pass/fail criteria.

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Figure 2

Thermocouple positions for the thermal barrier material test in CAN/ULC S101, Standard Methods of Fire Endurance Tests of Building Construction and Materials.

More importantly, with both standards, NBC requires the testing agency measure the temperatures at the interface of the foam plastic and thermal barrier. There have been recorded situations where tests have been run with the thermocouples on the backside of the assembly or with the thermocouples buried in the foam. Neither of these conditions would meet the requirements of NBC or the test standards mentioned above. The code is very clear in this respect. In the first category, NBC, in 3.1.5.12 (titled â&#x20AC;&#x153;Combustible Insulation and its Protectionâ&#x20AC;?), allows for the use of a thermal barrier based on certain criteria. In a building required to be of noncombustible construction, foamed plastic insulation having a flame-spread rating not more than 25 is permitted, provided the insulation is protected from adjacent space in the building by a thermal barrier that meets the requirements of classification B when tested in conformance with CAN/ULC S124. As a general rule, if one can see foamed plastic insulation in the conditioned space of a building, it is a code violation. This is a small-scale test, with an exposed surface area of 0.49 m2 (5.3 sf), requiring temperature measurements at the interface of the thermal barrier and the foamed plastic. Purely a thermal transmission test, it measures the effectiveness of the thermal barrier to insulate the foamed plastic from heat and fire. The test must be run in a horizontal orientation. The material is exposed to a fire that reaches 700 C (1290 F) after 10 minutes (Figure 1, page 42).

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Despite its small size, it is accepted as a severe test and one that provides an accurate measure of a thermal barrierâ&#x20AC;&#x2122;s effectiveness. Organizations such as ULC and Intertek indicate if a material has a Classification B rating based on CAN/ULC-S124. For a Classification B rating, the temperature rise at the interface of the tested thermal barrier material and the foamed plastic insulation cannot exceed an average of 140 C (252 F) for all the thermocouples or a maximum rise of 180 C (324 F) at any single thermocouple for 10 minutes (Figure 2, page 43). In the second and third categories, for buildings sprinklered throughout or 18 m (59 ft) or shorter (from grade to the floor level of the top storey), NBC requires a thermal barrier tested to CAN/ULC S124 for foamed plastic insulation having flame spread ratings between 25 and 500 if the building is sprinklered throughout, or not more than 18 m (59 ft) from grade to the floor level of the top storey. Otherwise, as in for taller buildings or those without sprinklers, thermal barriers must be tested to CAN/ULC-S101. This is a full-scale test, larger than CAN/ULC S124, requiring an exposed surface of 9.3 m2 (100 sf) that can be run in both horizontal and vertical orientations to evaluate the intended orientation of the thermal barrier. As per Section 3.1.5.12 of the 2012 NBC, it establishes whether a material qualifies as a thermal barrier as follows: 2. Combustible insulation having a flame-spread rating of more than 25 but not more than 500 is permitted in the exterior walls of a building required to be of noncombustible construction, provided the insulation is protected by a thermal barrier that, when tested in conformance with CAN/ULC-S101 will not develop an average temperature rise of more than 140 C or a maximum temperature rise more than 180 C at any point on its unexposed face [(i.e. the unexposed face of the thermal barrier, which is the interface of the foam and the thermal barrier)] within 10 minutes. 3. Combustible insulation, having a flame-spread rating of more than 25 but not more than 500 on any exposed surface, or any surface that would be exposed by cutting through the material in any direction, is permitted in the interior walls, within ceilings and within roof assemblies of a building required to be of noncombustible construction, provided the insulation is protected from adjacent space in the building by a thermal barrier that, when tested in conformance with CAN/ULC-S101 will not develop an average temperature rise of more than 140 C or a maximum temperature rise of more than 180 C at any point on its unexposed face within 20 minutes, and will remain in place for not less than 40 minutes. In addition to testing potential thermal barrier properties, CAN/ULC-S101 is primarily used to test the fire resistance of assemblies. However, for this type of testing, the thermocouples (and, therefore, temperature measurements) are located on the unexposed side of the assembly (Figure 3, page 45). This approach is different than what is used to assess a materialâ&#x20AC;&#x2122;s effectiveness as a thermal barrier. The use of CAN/ ULC-S101 in this fashion cannot be employed to approve thermal barriers because in this test procedure the thermocouples are not at the interface of the foam and thermal barrier as required by the National Building Code.

Current market situation Until recently, thermal barriers have typically been one of two typesâ&#x20AC;&#x201D;fibre-based or cementitious. These products protect the foamed plastic from fire, while also providing

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Image courtesy CUFCA

Figure 3

CAN/ULC S101 thermocouple position for fire resistance wall assembly test.

physical protection for the foam from abuse, allowing for longer in-place service life. Many of these materials have a long and successful track record, and are listed with testing agencies such as ULC, Intertek, and QAI, passing many CAN/ULC S124 or CAN/ ULC-S101 tests as thermal barriers. Recently, this author has seen unfounded claims by companies marketing paintable ignition barriers that are certified for use in Canada as thermal barriers. These products are often intumescentsâ&#x20AC;&#x201D;typically, ammonium polyphosphate-basedâ&#x20AC;&#x201D;which begin the intumescing process at 240 C (464 F), which is higher than the maximum allowable temperature limits of the code. (In other words, they begin their protective actions too late.) Unfortunately, in most cases, these companies have attempted to confuse the marketplace by intentionally running fire tests where the thermocouples were not properly located to comply with NBC. For example, in some cases, a single material was tested using CAN/ULC-S101 with the thermocouples on the unexposed side of the assembly, behind the wallboard. This procedure is appropriate for qualifying a wall assembly, but cannot be used to qualify a material as a thermal barrier (i.e. because such a process requires the thermocouples to be at the interface of the thermal barrier and the foam). Another inappropriate test had the thermocouples buried within the foam, which obviously does not meet the code. When this information was brought to the attention

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of one of the manufacturers that had run tests where thermocouples were not placed in accordance to the NBC requirements, the company stated it did not think the material would pass as a thermal barrier when using the required thermocouple placement. In addition to erroneously promoting products with claims their products are certified for use in Canada, some companies have been supplying results from testing in the United States done in accordance to UL 1715, Fire Test of Interior Finish Material—a completely different and less severe test method that does not meet NBC requirements. Thankfully, there has recently been the introduction of certain intumescent paints that do pass the CAN/ULC S124 test. By meeting the requirements of the test, these companies have negated the argument the CAN/ULC S124 test is too severe to act as a test method for intumescent thermal barriers. Further, there exists in Canada a process whereby developers of new materials may use the Canadian Construction Materials Centre (CCMC) to demonstrate compliance with the requirements of NBC or provincial/territorial building codes. Regretfully, this author has seen engineering judgments appearing to ‘okay’ the use of intumescent thermal barriers. In some instances, the claims made have been factually incorrect; in others, the basis for approvals have been the alternate method for code compliance provisions, given in 1.2 of Division A of NBC where compliance with the code can be achieved by meeting a prescriptive test or by showing through performance testing a product meets the objectives of the prescriptive code section. Considering the wide variety of thermal barriers choices now available, can one really state the alternate, but untested, product is as good as or better than those products currently available? This author does not believe such a claim can be made, especially when code-compliant test processes are available at a reasonable cost.

Contractor liability Ultimately, it is the responsibility of the installer of the thermal barrier and the AHJ to provide and approve products conforming to the relevant provincial building code. Unfortunately, the contractor may also be held liable if he or she installs a product that does not conform to the applicable standard—even when the building inspector has incorrectly accepted products that do not meet the intent of the NBC. Architects and specifiers could also face legal liability, to say nothing of the moral issues for design professionals. Canadian Construction Documents Committee (CCDC) documents suggest, it is the responsibility of the prime consultant to include in the contract documents the criteria required for the constructor to comply with the code requirements. It is the constructor’s responsibility to provide the work in compliance with the contract documents and the code.2 That said, the constructor is not responsible to verify the contract documents are in compliance with the code. The constructor may be liable if it installs a material not in compliance with the contract documents, or if it proposes a substitution material that does not meet the code requirements. The reality is all parties involved risk some legal liability, to say nothing of the moral issues. To avoid any unnecessary liability, the specifications should request a submittal of a letter from the manufacturer stating the material being supplied has been tested in accordance with the requirements of the National Building Code (item 3.1.5.12) and passed its criteria established for a thermal barrier. One should also ask for the test

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Photo courtesy W. R. Grace & Co.

Preparing the foam for a CAN/ULC S101 wall test.

report that supports the requested letter. There are many products in the market that have successfully passed the NBC criteria as thermal barriers; selecting and using a product that has not met these criteria would be taking on unnecessary liability, and is a threat to life safety. The fire protection industry (including manufacturers, engineers, architects, and the contractor community) has a duty to provide the public with a reasonable level of safety in buildings in compliance with the applicable building codes. It is the responsibility of all parties to perform their due diligence to ensure public safety is not put at undue risk. Accepting only code-conforming materials is an important aspect in the process.

Notes 1 A flashover fire occurs when the temperature in an area is high enough to ignite all flammable material simultaneously. This is usually created by a high concentration of gases within the atmosphere. Once that temperature has been reached, any ignition source will create a sudden explosion of fire throughout the area. 2 For more info, see CCDC 2-2008, Stipulated Price Contract, CCDC 5A-2010, Construction Management Contractâ&#x20AC;&#x201C;For Services, and CCDC 5B-2010, Construction Management Contractâ&#x20AC;&#x201C; For Services and Construction.

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