The Superior Thermal Performance of ICF Lintels over Wood Lintels

Glasgow schooluc

Quick and easy to install Fox Blocks insulated concrete lintels provide superior thermal performance over wood-lintels. Fox Blocks ICF lintels help create healthy homes and buildings with low maintenance and disaster-resistance.

Why Do Building Openings Need Lintels?

Builders install lintels (beams) along the top of windows, doors, and other openings in a building or home to support the loads from the above floor or roof. The lintel transfers the load to the supports along the sides of the openings.

Wood Lintels vs. ICF Lintels

When it comes to energy-efficiency, ICF lintels provide a significant advantage over wood lintels.

Wood Lintels

Wood lintels diminish the thermal performance around the opening.

Installing a lintel on a wood-framed structure typically involves doubling or tripling a 2”x8” or 2”x12” between the jack (double) studs on the sides of the opening, which reduces or eliminates the wall cavity and limits the placement of insulation over the opening - ultimately diminishing the building’s thermal performance by creating a substantial thermal bridge and reducing the insulating value to about R-9 or less.

ICF Lintels

When building ICF lintels, contractors use a regular, high thermal mass ICF block, with reinforcement bars inside the concrete core. The process does not comprise the thermal performance around the opening like the application of wood lintels. In fact, the thermal performance of Fox Blocks ICF lintels, for all openings, maintains the system's full thermal capacity of R-23.

Installing an ICF Lintel

The design of ICF lintels should follow ACI 318-14 Building Code Requirements for Structural Concrete acting as beams spanning over wall openings. For optimum performance, the installation of ICF lintels must follow manufacturer's specific reinforcement requirements, commonly based on the following criteria:

  • The load conditions
  • The depth of the lintel
  • The width of the opening
  • The concrete strength
  • The wall thickness

Fox Blocks provides engineered lintel tables for installing lintels in Fox Block ICF walls. Contractors can use the information from the tables during the building process and for submission to the local building department. However, there are two construction situations that cannot utilize the tables and therefore require special engineering:

  1. Non-rigid lintels fixed against rotation, and
  2. The superimposed and uniformly distributed load on the lintel (i.e., there are no concentrated point loads)

Most ICF lintels installations involve the following steps:

  1. Install the standard ICF over the top of the opening and place the top horizontal rebar into position.
  2. Lay the lower horizontal reinforcing steel rebar on top of the lintel above the opening so that it extends a minimum of 24 inches (610 mm) past each side of the opening. If placing two lengths or more of rebar, tie wire them together.
  3. Clip the top rebar into the reinforcement notches (cradles) located on the top of the webs.
  4. Measure and bend the stirrups in a C or S shape. Hook the stirrups around the top rebar and use them to support the bottom rebar(s). The installation instruction specifies the stirrup dimensions and required spacing.
  5. To keep the walls straight, install a course of Fox Blocks HV clips horizontally over the openings.
  6. Install vertical rebar, as required, in the ICF wall on both sides of the opening.
  7. Prior to concrete placement, confirm the lintel rebar has been placed over every opening as per the engineering requirements.

More Benefits of Fox Blocks ICF Lintels

Beside superior thermal performance, Fox Blocks ICF lintels offer numerous other advantages over wood lintels:

  • They maintain a perm rating of less than 1.0, which controls moisture intrusion and stops the growth of unhealthy and damaging mold.

Wood lintels may absorb moisture, which can cause swelling, shrinking, and mold - all of which can lead to expensive repairs.

  • They have a fire-resistance rating (ASTM E119) of 4 hours for the 6-inch blocks and 2 hours for the 4-inch blocks.

Wood lintels are especially susceptible to fire damage, particularly during construction and before the application of fire protection to the structure.

Wood lintels may contain adhesives, chemicals, and VOCs that compromise indoor air quality.

  • They are less prone to termite damage than wood lintels because they lack organic material, which termites eat. For termite protection waterproofing, Fox Blocks recommends the application of Polyguard Products, Inc. 650 XTM or 650 XTP membranes.

The thermal performance of Fox Blocks easy-to-install ICF lintels plus the use of the Fox Blocks EPS buck system, far exceeds that of wood lintels. Fox Block lintels are low maintenance, disaster-resistant, and will provide a healthy home or building. For more information on how ICF construction creates high-performing and energy-efficient buildings and homes, please refer to the Fox Blocks website.