Tech Talk:  CLT and Continuous Insulation (Ci): A Perfect Match

Cross Laminated Timber (CLT) is gaining popularity as a building method due to its numerous advantages. Made from renewable dimensional lumber laminated in cross-directional layers, CLT is not only structurally sound but also offers a range of benefits that make it ideal for low- and mid-rise buildings. These include:

• Fabrication to custom thicknesses, sizes, and openings off-site.
• Fast field installation.
• Good fire resistance and sound-dampening properties.
• Use as structural walls, floors, and roof/ceiling assemblies.
• Environmental sustainability.

Architects, designers, engineers, and building owners appreciate these qualities and are increasingly incorporating CLT into structures across North America.

The Role of Insulation in CLT Construction

While CLT inherently has an R-value due to its dimensional lumber makeup—typically 1.25 per inch of thickness (C or U-factor of 0.80)—this alone is often insufficient to meet the minimum R-values or U-factors required by the 2024 International Energy Conservation Code (IECC) in many climate zones.

For example:

• A 3.9" CLT wall has an R-value of 4.9.
• A 9.4" CLT roof has an R-value of 11.75.

In Climate Zones 5 and 6, additional insulation is necessary to achieve the IECC’s minimum requirements for walls (R-19.5) and roofs (R-31.25). One of the best strategies for achieving these standards is adding continuous insulation (Ci) to the exterior of CLT structures.

R-Shield®: The Ideal Ci Solution for CLT

Premier Building Systems offers a variety of R-Shield Ci products, with or without sheathing and facers, designed to complement CLT construction and meet IECC requirements. These include:

• R-Shield Insulation
• Nailbase
• Nailstrip
• PLUS Film-Faced Products

For this example, we’ll focus on R-Shield Nailbase, an insulation board laminate made of R-Shield Graphite Polystyrene (GPS) and 7/16” OSB.* R-Shield Nailbase is screw-applied to the exterior of CLT walls and roofs, with the OSB facing outward to support wall or roof claddings.

Meeting 2021 Onward IECC Requirements with CLT and R-Shield Nailbase

Let’s break down an example project:

• Project Type: 3-story light commercial office building.
• Roof Slope: 3” in 12”.
• Project Locations: Reno, NV; Salt Lake City, UT; or Denver, CO.
• Climate Zones: 5 & 6 under the 2024 IECC.

IECC Insulation Requirements:

• Walls: U-factor ≤ 0.051 (R-value ≥ 19.5).
• Roofs: U-factor ≤ 0.032 (R-value ≥ 31.25).

CLT Walls

• A 3.9" CLT wall provides R-4.9.
• Additional R-14.7 is needed to meet R-19.5.
• Solution: R-Shield Nailbase at 3.5" thickness provides R-14.7, achieving the IECC minimum when combined with the CLT’s R-4.9.

CLT Roofs

• A 9.4" CLT roof provides R-11.75.
• Additional R-19.5 is needed to meet R-31.25.
• Solution: R-Shield Nailbase at 4.5" thickness provides R-19.5, achieving the IECC minimum when combined with the CLT’s R-11.75.

These examples demonstrate how the appropriate thicknesses of R-Shield Nailbase applied to CLT walls and roofs can meet IECC insulation requirements while delivering a high-performance building envelope. Explore more on using the performance method and U-factors in various building envelope assemblies to meet 2021 and the upcoming 2024 building code here. 

Additional Benefits of R-Shield Ci Products

Beyond meeting IECC standards, R-Shield Ci products offer enhanced functionality for CLT structures, including:

• Rain screen capabilities.
• Factory-applied weather resistive barriers.
• A variety of configurations tailored to specific project needs.

A Perfect Match for CLT Construction

R-Shield Ci products, including Nailbase, are the ideal solution for achieving energy code compliance and high-performance building envelopes in CLT structures. To learn more about integrating R-Shield products into your CLT projects, contact a Premier Building Systems representative today. Our team is here to help you design durable, efficient, and sustainable buildings that exceed expectations.

*Greater thicknesses of OSB, plywood, or FR plywood can be specified for specific wall or roof assemblies.

Want to learn more about incorporating insulated nail base and our continuous insulation on your projects? Reach out to your local Rep here.