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.
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:
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.
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.
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.
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.
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.
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.
An interior application of CCSPF is recommended for this system and typically has the following properties:
Use of alternative insulation types should be carefully considered along with a project’s specific application and exposure.
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.
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.
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.
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.
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.
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.
LEGENDPreservative-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.
LEGENDAnchor locations for rough opening preservative-treated blocking should be confirmed with the project’s structural engineer.
LEGENDThe 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.
LEGENDThe 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.
LEGENDThe 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.
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.
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:
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.
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.
The following are modeling variables specific to this system:
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.
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 5-1 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.
Fig. 5-7 System 5 insulation options reflected in the three-dimensional thermal modeling results shown in Table 5-2
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 5-3 System 5 CMU wall with interior insulation pricing summary