System 5:
Interior-Insulated CMU Wall

System 5:
Interior-Insulated CMU Wall

General Info

Masonry system 5 is a mass wall system with a concrete masonry unit (CMU) wall structure and interior insulation. The components of this system, from interior to exterior, are described in Fig. 5-1. This system is most appropriate for low- to mid- rise commercial applications but may be used for residential applications as well as some high-rise structures. An example application of this system is shown in Fig. 5-2 on page 5-2.

Building Enclosure Control Layers

As noted in the introductory chapter, an above-grade wall system controls liquid water, air, heat, and possibly water vapor to function as an effective and durable environmental separator. This system controls these elements with the following control layer systems and/or materials:

  • The water control layer, primarily comprising the mass CMU wall
  • Air control layer, comprising the air barrier system
  • Thermal control layer, comprising thermal insulation and other low- conductivity materials
  • Vapor control layer, comprising vapor retarding materials.

For a summary of the relationship between building enclosure loads, control layers, and associated systems and materials, refer to Fig. i-13 on page i-21 of the Introduction.

Fig. 5-3 illustrates the water- shedding surface and control layer locations. The control layers for typical system details are also provided adjacent to each detail at the end of this chapter.

As shown in Fig. 5-3, the water-shedding surface occurs at the CMU wall face. The water control layer exists within the CMU wall structure. Both the air control layer and the vapor control layer occur through the depth of the closed-cell spray foam insulation (CCSPF). The CCSPF, or other interior and cavity thermal insulation as discussed within this chapter, provides the thermal control layer.

Water-Shedding Surface

The water-shedding surface is a system that serves to reduce the water load on the enclosure. A general discussion of the water-shedding surface is provided in the Water-Shedding Surface discussion on page i-19.

The CMU block and mortar provide the water-shedding surface of this system. Additional water-shedding surface components include sheet-metal flashings and drip edges, sealant joints, and fenestration systems as shown on the details included at the end of this chapter.

Water-repellent admixtures are added to the block and mortar of this system and a surface-applied clear-water repellent is also recommended. These repellents serve to encourage water shed—along with other measures such as tooled “V” or concave shape (preferred) mortar joints, sufficient sheet-metal parapet cap design, and other general design recommendations as discussed in the Northwest Concrete Masonry Association (NWCMA) TEK Note on Rain-Resistant Architectural Concrete Masonry.1

The water-shedding surface is most effective when free of gaps; therefore, movement joints and joints around fenestrations and penetrations should be continuously sealed with a backer rod and sealant.

Water Control Layer

The water control layer is a continuous control layer that is designed and installed to act as the innermost boundary against water intrusion. For this system, the CMU block, mortar, and grout (inclusive of any integral water repellents) assist to provide the water control layer.

The water control layer is made continuous with the help of flashing membranes at parapet tops, fluid- applied flashings at fenestration rough openings, sealant joints, and fenestration systems as shown on the details included at the end of this chapter.

The CCSPF insulation at the interior face of the CMU structure may also provide additional rain penetration resistance.

The water control layer must be continuous across the wall face to serve as an effective control layer. Whereas this wall manages water at the CMU face and may manage some water at the CCSPF layer, window rough openings between these two planes must also have a water control system or material. Typically, this is a fluid-applied flashing membrane that is also part of the air control layer. It protects rough openings against water intrusion, minimizes air leakage, and is depicted in the details at the end of this chapter.

Air Control Layer

The air barrier system provides the air control layer. In addition to controlling air, this layer also assists with controlling liquid water, heat, and water vapor. A general discussion of the air control layer and the air barrier system is provided in the Air Control Layer discussion on page i-26.

The air barrier system in this system is typically the CCSPF interior of the CMU wall structure and has the air permeance properties described in the Design Checklist discussion on page i-44.

To serve as an effective air barrier system and to reduce the risk of air leakage condensation on the interior CMU face or steel-framing within this masonry system, CCSPF should be installed continuously up to rough openings, penetrations, and roof and floor structures.

When installing CCSPF, it is important to install the insulation in strict conformance with the manufacturer’s installation instructions. Improper installation could lead to premature cracking and delamination from the substrate, which can allow air to move between the insulation and substrate and increase condensation risk. Improper installation can also lead to risk of fire during installation. It is recommended that only experienced applicators who are approved by the CCSPF product manufacturer are used.

Other considerations when using CCSPF insulation includes fire propagation and volatile organic compound (VOC) compliance. Make sure product selection, application, and use all comply with local jurisdiction requirements.

Vapor Control Layer

The vapor control layer retards or greatly reduces (e.g., vapor barrier) the flow of water vapor due to vapor pressure differences across the enclosure. Unlike the other control layers presented in this guide, the vapor control layer is not always necessary or required to be continuous.

In this wall system, the vapor control layer occurs throughout the depth of the CCSPF. CCSPF insulation has a minimum 2 lb/ft3 density (per ASTM C5184) and is typically applied at a minimum of 2-inches to be considered a Class II vapor retarder.

Because this system is insulated to the interior, it is important that the CCSPF (as the air, vapor, and thermal control layers) is continuous across the wall’s interior face and up to rough openings and penetrations to minimize the risk of condensation on cooler surfaces.

Thermal Control Layer

The thermal control layer controls heat flow and assists with controlling water vapor.

In this wall system, the interior CCSPF insulation serves as the thermal control layer. At transition details, the thermal control layer includes interior insulation across bond beams and up to rough openings, windows and doors, and roof assembly insulation as well as slab and foundation insulation.

The thermal control layer should be as continuous as possible across the system to minimize heat loss, reduce condensation risk, and improve occupant thermal comfort. Continuity of interior insulation can be difficult to achieve at areas such as floor line slab edges and some wall-to-roof transitions. These transitions should be carefully considered for whole-building energy performance implications as well as for energy code compliance and other building code requirements.

The CMU wall of this wall system is also a thermal mass; thus, it may provide thermal mass benefits as discussed in the introductory chapter.

Additional thermal insulation discussion is provided in the Thermal Performance and Energy Code Compliance discussion on page i-33 of the Introduction and the Thermal Performance and Energy Code Compliance discussion on page 5-7 of this chapter.

Insulation Selection

An interior application of CCSPF is recommended for this system and typically has the following properties:

  • Air Permeance: Meets the maximum air permeance properties described in the Design Checklist discussion on page i-44.
  • Water Vapor Transmission: Less than 1 perm at 2-inch thickness when tested to ASTM E96.5
  • Closed-Cell Content: Exceeds 95% when tested to ASTM D6226.6
  • Density: Approximately 2 lb/ft3 when tested to ASTM C518.4

Use of alternative insulation types should be carefully considered along with a project’s specific application and exposure.

  • Vapor- and Air-Permeable Insulation. This includes fiberglass and mineral fiber batt or semi-rigid mineral fiber insulation. These products alone do not serve as air, water, and vapor control layers; thus they require additional materials or systems be implemented into the system. When additional materials are implemented to serve as these control layers, carefully consider the risk for condensation on the interior face of the CMU wall. Lack of a fully adhered water control layer membrane, such as a fluid-applied membrane, at the interior or exterior face of this wall system may also reduce the rain penetration resistance of the system when compared to the CCSPF insulation strategy.
  • Rigid Board Insulation. This includes extruded polystyrene (XPS) or moisture- resistant foil-faced polyisocyanurate insulation products. These products provide an air and vapor control layers at the interior face of the product, which is fully taped and/or sealed at seams, edges, and penetrations and to perimeter elements such as floor slabs and roof structures. Rigid board insulation products require notching around wall projections such as roof joists and pipe penetrations; thus, additional insulating and air (and possibly vapor) sealing mechanisms at these locations can provide a continuous barrier. Rigid board insulation products do not provide continuous adhesion to the CMU wall structure like a CCSPF product does. As a result, if water is allowed to bypass the CMU wall structure, it is not contained within the wall but instead may reach horizontal elements. This risk can be minimized by stepping foundation elements to terminate the insulation at a lower elevation than the floor slab and by installing an elastomeric coating to the exterior wall face (see Elastomeric Coatings discussion on page i-62).

 

Fig. 5-3 System 5 water-shedding surface and control layer location

Fig. 5-3 System 5 water-shedding surface and control layer location

Install steel studs prior to installation of the continuous CCSPF layer as shown in Fig. 5-4. This eliminates the difficulty of installing studs against the irregular surface of the first li and allows continuity of the CCSPF when multiple li s are installed.

Although masonry is defined as a noncombustible cladding material, the use of a combustible air barrier and WRB system product or foam plastic insulation products within a wall cavity can trigger fire propagation considerations and requirements. Depending on the local jurisdiction, IBC Section 1403.52 regarding vertical and lateral flame propagation as it relates to a combustible air barrier and WRB system may require acceptance criteria for NFPA 285.3 The use of foam plastic insulation within a wall cavity should also be addressed for IBC Chapter 262 provisions.

Fig. 5-4 Closed-cell spray foam insulation installed between steel studs.

Fig. 5-4 Closed-cell spray foam insulation installed between steel studs.

Movement Joints

Because CMU is a concrete product, it will shrink over time (along with the mortar) due to initial drying, temperature fluctuations, and carbonation. Not only will shrinkage movement need to be considered, but differential movement between the CMU structure and other structural elements due to deflection, settlement, and various design loads will also need to be addressed.

Crack control within the CMU can increase the rain penetration resistance of this system. Material properties and reinforcing methods of the CMU structural wall should be implemented to reduce cracking; however, control joints within the CMU wall also need to be implemented to provide a plane of weakness to reduce shrinkage stresses and provide continuity of the water-shedding surface at these locations. Control joints in CMU can be constructed in a number of ways. Regardless of the method used, a continuous backer rod and sealant joint is installed at the joint to assist with water shedding and to provide a continuous water control layer.

Refer to the Movement Joints discussion on page i-48 for more information on locating joints and sealant joint best practices.

Structural Considerations

The CMU block wall of this system provides the primary structure of this system. It is the responsibility of the Designer of Record to ensure that all structural elements of the wall are designed to meet project-specific loads and local governing building codes. Generic placement of the grout, reinforced elements, and supports/anchors is demonstrated within the details of this chapter and is provided for diagrammatic purposes only.

CMU Wall

The CMU in this system complies with ASTM C90,10 mortar designed for the CMU conforms to ASTM C27011 or ASTM C171412 when specifying preblended mortar. The mortar type selected should be appropriate for the CMU application; Type S is typically specified. Grout components should comply with ASTM C 47613 while aggregate within the grout should comply with ASTM C 404.14

Block and mortar are both specified with a water-repellent admixture as discussed in the Water Repellents discussion within this chapter. Additionally, refer to the Northwest Concrete Masonry Association (www.nwcma.org) for additional information on specifying block, mortar, and grout.

Install the CMU and mortar joints of this system in conformance with industry- standard best practices, manufacturer requirements, and guidelines outlined in the NWCMA Tek Note on Rain-Resistant Architectural Concrete Masonry;1 appropriate product selection and installation of CMU and mortar materials is necessary to provide a durable and water-resistive cladding system.

A qualified Designer of Record should design and review the specifics of the architectural characteristics and structural properties of the block, mortar, grout, and reinforcing. Various industry resources are available to assist with CMU wall design and are listed in the Resources section at the back of this guide.

Corrosion Resistance

For sheet-metal flashings that are integrated within this system (including flashings and sheet-metal drip flashings), it is best practice to provide components that are manufactured of ASTM A66615 Type 304 or 316 stainless steel, which are nonstaining and resistant to the alkaline content of mortar and grout materials. Consider prefinishing sheet-metal where stainless steel sheet-metal flashing components are not economically feasible or aesthetically desirable. Where used, this guide recommends the base sheet metal be a minimum G90 hot-dipped galvanized coating in conformance with ASTM A65316 or minimum AZ50 galvalume coating in conformance with ASTM A792.17 Coating the exposed top finish of the sheet metal with an architectural-grade coating conforming to AAMA 62118 is recommended.

Water Repellents

Both integral water-repellent admixtures and a surface-applied clear water repellent are used in this system and assist with reducing the water absorption of the CMU wall and encourage water shedding. Use water-repellent admixtures both in the CMU and mortar. Admixture within block units should comply with NCMA TEK 19-7,19 while mortar admixture should comply with ASTM C1384.20 More discussion on surface-applied clear water repellents is provided in the Surface- Applied Clear Water Repellents discussion on page i-59.

Make sure that both CMU and mortar admixtures as well as surface-applied water repellents have known compatibility performance.

Details

Typical Window Head (Detail 5-A)

Chapter 5 Details 5-ALEGEND

  1. Typical Assembly:
    – Interior gypsum board
    – Steel-framed wall
    – Closed-cell spray foam insulation between studs (CCSPF)
    – 2 inches CCSPF
    – Single-wythe CMU wall with water-repellent admixture
    – Clear water-repellent
  2. Preservative-treated wood blocking and plywood
  3. Sealant over backer rod
  4. Fluid-applied flashing membrane
  5. Continuous back dam angle at rough opening perimeter, minimum 1-inch tall, with window fastened through the back dam angle per window manufacturer recommendations.
  6. Continuous air barrier sealant, tie to continuous seal at window perimeter
  7. Storefront window

Detail Discussion

  • A sheet-metal flashing as shown in Chapter 4 in Fig. 4-6 on page 4-15 may also be considered.
  • Air control layer continuity is provided by the CCSPF fluid-applied flashing membrane at the rough opening and the air barrier sealant transition to the storefront window.
  • Water control layer continuity is provided at the CMU wall, fluid-applied flashing membrane at the rough opening, and the air barrier sealant transition to the storefront window.
  • Preservative-treated blocking and plywood provide a low–thermal conductivity structural support for the window perimeter and a suitable substrate for the fluid-applied flashing membrane application.

Chapter 5 Details 5-A

Precast Windowsill (Detail 5-B)

Chapter 5 Chapter 5-BLEGEND

  1. Typical Assembly:
    – Interior gypsum board
    – Steel-framed wall
    – Closed-cell spray foam insulation between studs (CCSPF)
    – 2-inches CCSPF
    – Single-wythe CMU wall with water-repellent admixture
    – Clear water-repellent
  2. Storefront window on minimum 1/4-inch-thick intermittent shims
  3. Sealant over bond breaker tape
  4. Sloped sheet-metal sill flashing with hemmed drip edge
  5. Drainage mesh or minimum 1/4-inch-thick intermittent shims
  6. Fluid-applied flashing membrane
  7. Preservative-treated wood blocking and plywood
  8. Sloped precast concrete sill
  9. Continuous air barrier sealant, tie to continuous seal at window perimeter
  10. Continuous back dam angle at rough opening perimeter, minimum 1-inch tall, with window fastened through the back dam angle per window manufacturer recommendations.

Detail Discussion

  • Air control layer continuity is provided by the CCSPF, the fluid-applied flashing membrane at the rough opening, and the air barrier sealant transition to the storefront window.
  • Intermittent shims below the storefront window and sheet-metal sill flashing encourage drainage of the window rough opening to the exterior environment.
  • The sheet-metal sill flashing promotes water shedding at the sill area and protects the fluid-applied air barrier/WRB flashing from UV exposure. The projected precast sill also promotes watershed away from the wall face.
  • Anchor locations for rough opening preservative-treated blocking should be confirmed with the project’s structural engineer.

Chapter 5 Detail 5-B

Storefront Window Jamb (Detail 5-C)

Chapter 5 Detail 5-CLEGEND

  1. Typical Assembly:
    – Interior gypsum board
    – Steel-framed wall
    – Closed-cell spray foam insulation between studs (CCSPF)
    – 2-inches CCSPF
    – Single-wythe CMU wall with water-repellent admixture
    – Clear water-repellent
  2. Storefront window
  3. Sealant over backer rod
  4. Preservative-treated wood blocking and plywood
  5. Fluid-applied flashing membrane
  6. Continuous air barrier sealant, tie to continuous seal at window perimeter
  7. Continuous back dam angle at rough opening perimeter, minimum 1-inch tall, with window fastened through the back dam angle per window manufacturer recommendations.

Detail Discussion

  • Air control layer continuity is provided by the CCSPF, fluid-applied flashing membrane at the rough opening, and the air barrier sealant transition to the storefront window.
  • The sealant and backer rod joint between the storefront window and CMU wall provides water shedding surface continuity between the CMU wall and window face.
  • The continuous back dam angle shown allows for perimeter attachment of the storefront window without the need for F-clips or similar anchors, which o en inhibit the air barrier sealant (and thus, the air control layer) at the window perimeter. Project-specific window attachment methods should be confirmed with the window manufacturer during the design phase of the project.

Chapter 5 Detail 5-C

Slab and CMU Foundation (Detail 5-D)

Chapter 5 Detail 5-DLEGEND

  1. Typical Assembly:
    – Interior gypsum board
    – Steel-framed wall
    – Closed-cell spray foam insulation between studs (CCSPF)
    – 2-inches CCSPF
    – Single-wythe CMU wall with water-repellent admixture
    – Clear water-repellent
  2. Rigid XPS insulation
  3. Underslab vapor barrier
  4. Rigid XPS underslab insulation
  5. Hardscape joint at sidewalk
  6. Damp proofing
  7. Drainage composite or gravel backfill

Detail Discussion

  • The XPS insulation provides a thermal break between the slab and CMU wall and allows for a continuous thermal control layer at the slab-to-wall transition.

Chapter 5 Detail 5-D

Typical Parapet at Inverted Roof Membrane Assembly (Detail 5-E)

Chapter 5 Detail 5-ELEGEND

  1. Typical Assembly:
    – Interior gypsum board
    – Steel-framed wall
    – Closed-cell spray foam insulation between studs (CCSPF)
    – 2-inches CCSPF
    – Single-wythe CMU wall with water-repellent admixture
    – Clear water-repellent
  2. Inverted roof membrane assembly
  3. Typical Parapet Assembly:
    – Inverted roof membrane
    – Single-wythe CMU wall with water-repellent admixture
    – Clear water repellent
  4. Sloped standing-seam sheet-metal coping with gasketed washer fasteners
  5. Preservative-treated wood blocking
  6. High-temperature self-adhered membrane

Detail Discussion

  • The sheet-metal coping with hemmed drip edge sheds water away from the wall top and CMU wall face below. It is recommended that the sheet-metal cap counterflash the top course of block by a minimum of 3-inches.
  • The CCSPF extends tight up to the underside of the deck, around roof structure and anchor elements. This reduces the opportunity for warm, moisture-laden interior air to contact the deck and CMU wall where it’s coldest. It also provides air control layer continuity from the wall insulation to the metal pan deck assembly.

Chapter 5 Detail 5-E

Parapet Assembly Section Cutaway (Interior) (Detail 5-F)

LEGEND

  1. Single-wythe CMU wall with water-repellent admixture
  2. Preservative-treated wood blocking and plywood anchored to CMU wall
  3. Roof structure
  4. Steel-framed wall
  5. Sloped, preservative-treated wood blocking
  6. Inverted roof membrane assembly
  7. High-temperature self-adhered membrane
  8. Sloped standing-seam sheet-metal coping with gasketed washer fasteners
  9. Continuous back dam angle at rough opening perimeter, minimum 1-inch tall, with window fastened through the back dam angle per window manufacturer recommendations.
  10. Continuous air barrier sealant, tie to continuous seal at window perimeter.
  11. Storefront window
  12. CCSPF
  13. Interior gypsum board

3-D Detail Discussion

  • Three-dimensional cutaway sections on the next three pages represent two-dimensional details of this system.
  • The preservative-treated blocking and plywood, as shown in Detail 5-F, at the window rough opening provide a low thermal conductivity structural support for the window perimeter and also provide a suitable substrate for the fluid-applied flashing membrane. The preservative-treated blocking and plywood is 2-inches deep to accommodate the minimum continuous CCSPF depth necessary to achieve a Class II permeance (vapor retarder).
  • As shown in Detail 5-F, the steel studs bridge the interior 2-inches of CCSPF. The steel-stud framing may be moved inboard of the insulation entirely to eliminate thermal bridging and improve the system’s thermal performance. See Fig. 5-7 on page 5-11 and the related text discussion for additional insulation options.
  • As shown in Detail 5-G, The XPS insulation provides a thermal break between the slab and CMU wall and allows for a continuous thermal control layer at the slab-to-wall transition.
  • Detail 5-H describes a typical rough opening with continuous back dam angle. The sill back dam angle creates a sill pan below the window; intermittent shims below the storefront window promote drainage at the sill and below the sheet-metal sill flashing.

Assembly 5 Detail 5F

Base-of-Wall Cutaway Section (Detail 5-G)

LEGEND

  1. Concrete floor slab over XPS insulation and vapor barrier
  2. Single-wythe CMU wall with water-repellent admixture
  3. Damp-proofing
  4. Drainage composite or gravel backfill
  5. Hardscape, sloped away from structure
  6. Hardscape sealant joint between hardscape and CMU wall
  7. Steel-framed wall
  8. CCSPF insulation per assembly
  9. Sloped sheet-metal sill flashing
  10. Fluid-applied flashing membrane
  11. Storefront Window
  12. Sloped precast concrete sill

Chapter 5 Detail 5-G

Window Jamb and Sill Section Cutaway Section (Detail 5-H)

LEGEND

  1. Single-wythe CMU wall with water-repellent admixture
  2. Minimum 1/4-inch-thick intermittent shims
  3. Continuous back dam angle at rough opening perimeter, minimum 1-inch tall, with window fastened through the back dam angle per window manufacturer recommendations.
  4. Sloped precast concrete sill
  5. Fluid-applied flashing membrane
  6. Continuous air sealant, tie to continuous seal at window perimeter.
  7. Storefront window
  8. Sloped sheet-metal sill flashing over drainage mesh or minimum 1/4-inch-thick intermittent shims
  9. Sealant over backer rod, continuous at window perimeter

Chapter 5 Detail 5-H

Specifications

Thermal Modeling

Thermal Performance and Energy Code Compliance

This wall system is typically classified as a mass above-grade wall for energy code compliance purposes. Prescriptive energy code compliance values for this wall system are summarized in Table 5-1 on page 5-10 and describe:

  • Minimum insulation R-values for a prescriptive insulation R-value method strategy.
  • Maximum system U-factors for a prescriptive assembly U-factor method strategy. Note that the equivalent effective R-value of this U-factor has been calculated and is denoted in parenthesis ( ) for easy comparison to thermal modeling results included within this chapter.
  • Footnote (2) for compliance by exception. The ability to use this option depends on the jurisdiction, building’s use, and availability of CMU cores to be filled with insulation. If this exception is to be used, refer to the Chapter 4 Thermal Performance and Energy Code Compliance discussion on page 4-5.

For all energy code compliance strategies except the prescriptive insulation R-value method strategy, this wall system’s U-factor will need to be calculated or determined from tables; however, it may or may not be required to be less than the prescriptive U-factors in Table 5-1.

The Thermal Performance and Energy Code Compliance discussion on page i-33 and Fig. i-26 on page i-39 of the introductory chapter describes the typical process of navigating energy code compliance options. Additionally, the thermal modeling results demonstrated in this chapter may be used to assist with selecting wall system components (e.g., insulation R-value/inch and placement relative to steel studs, etc.) to achieve a target U-factor. Options for thermally optimizing this wall system, as determined through the modeling results, are also discussed.

System Effective Thermal Performance

The depth and location of the steel studs in this system will impact the system’s effective thermal performance depending on their placement relative to the system’s interior insulation. As shown in Fig. 5-5 and Fig. 5-6, various levels of thermal bridging can occur depending on the steel stud placement relative to the CMU and insulation. This thermal bridging reduces the system’s effective thermal performance.

Three-dimensional thermal modeling demonstrates this system’s effective thermal performance with various framing locations (relative to the insulation and CMU wall) and insulation thicknesses. A discussion on the modeling performed for this guide is included in the Appendix.

Thermal  Modeling: Variables

The following are modeling variables specific to this system:

  • Wall Structure: An 8-inch medium-weight block.
  • Wall Framing: Galvanized steel studs at 16-inches on-center, including a top and bottom track. Various system options for locating framing relative to insulation are considered and depicted in Fig. 5-7 on page 5-11.
  • Insulation: Cavity insulation is either R-15 batt insulation or R-6/inch insulation, such as CCSPF. Continuous insulation is either R-5 or R-6/inch; typical R-values for either rigid XPS or CCSPF insulation, respectively.

Thermal Modeling: Results

Modeling results are shown in Table 5-2 on page 5-11 and demonstrate the system’s effective R-value under various conditions. Of the modeling results presented, many of the insulation strategies provide an effective R-value that satisfies the various prescriptive energy code requirements shown in Table 5-1. Key points for thermally optimizing this wall system are italicized in boldface.

  • Options 2, 4, 5, 7, and 8 from Table 5-2 on page 5-11 provide an effective R-value in excess of R-20. In comparison to the remaining options, the greatest R-values achieved for this system are those that provide continuous insulation or continuous insulation with cavity insulation. When thermally optimizing this wall system, it is more effective to provide unbridged continuous insulation or continuous insulation in addition to cavity insulation.
  • Cavity-only insulation produces an effective R-value of 7.2 for 2-inches of CCSPF (Option 1) and an effective R-value of 9.1 for 4-inches CCSPF (Option 6). These options reduce the thermal performance of the insulation by 53 to 67%. The steel studs and CCSPF may still provide a vapor control layer for this wall system; however, the insulation is de-bridged from the CMU at vertical framing and at head and sill tracks, creating discontinuities in the air control layer (and sometimes in the water control layer). Cavity-only insulation for this system is a poor insulation strategy for thermal control and may be a poor strategy for air, water, and vapor control depending on the type of insulation and other materials used within the system.

Project-specific thermal performance values for the opaque above-grade wall should be used for energy code compliance and determined from a source that is approved by the authority having jurisdiction. Thermal performance sources may include the appendices of the 2015 WSEC7, ASHRAE 90.18, Comcheck9, thermal modeling and calculation exercises, or other industry resources.

Table 5-2 Assembly 5 prescriptive energy code compliance values.

Table 5-1 System 5 prescriptive energy code compliance values

Although the insulation strategies shown at right may meet the opaque wall prescriptive energy code requirements, additional considerations for how the various insulation strategies impact the remaining control layers is an important consideration.

Table 5-2 System 5 effective R-value comparison chart. Insulation options are described in Fig. 5-7.

Table 5-2 System 5 effective R-value comparison chart. Insulation options are described in Fig. 5-7.

Fig. 5-7 System 5 insulation options reflected in the three-dimensional thermal modeling results shown in Table 5-2

Fig. 5-7 System 5 insulation options reflected in the three-dimensional thermal modeling results shown in Table 5-2

Pricing Analysis

A pricing summary for this system is provided on Table 5-3 on page 5-15. Pricing demonstrates the relative price per square foot and is based on a 10,000-square- foot wall area with easy drive-up access. Pricing provided does not include interior finishes or steel framing components. Pricing is valid for 2018. Current pricing is also available at www.masonrysystemsguide.com.

Table 5-4 Assembly 5 CMU wall with interior insulation pricing analysis.

Table 5-3 System 5 CMU wall with interior insulation pricing summary