FAQ: Precast Insulated Wall Panels

Want quick responses to our most asked precast questions? Our blog series, “FAQ Fridays,” is designed to answer your most popular questions, organized by topic and product category. In Part 11 of this series, we discuss Precast Insulated Wall Panels.

What are insulated precast concrete panels?

Precast insulated wall panels (sometimes referred to as precast concrete sandwich panels) are a complete, inclusive and efficient building enclosure system: water, vapor, and thermal barriers all in one product—just add windows and doors!
Whether derived from reduced energy and operating costs, lower maintenance costs, improved functionality or productivity, or continued operational capability after a catastrophic event, a high-performance building offers its owners a greater return on investment than a conventional building.

High-performance precast concrete insulated wall panels, also known as precast concrete sandwich panels, can provide significant contributions toward these goals. These panels are composed of two wythes of concrete separated by a continuous (edge-to-edge) layer of insulation. Panels can be bearing walls, supporting gravity loads, as well as resist wind, seismic, and blast loads, or they can be cladding (non-loadbearing) panels transmitting wind, seismic, and blast loads to the structural frame and foundation. Precast insulated wall panels provide a versatile and economical means to meet the structural, thermal, moisture, and architectural requirements of a structure.

What are the benefits of precast insulated wall panels?

Insulated precast concrete panels offer a range of benefits that make them a preferred choice for efficient, resilient, and high-performance construction. Some of these advantages include: faster construction, high thermal performance, fire resistance, durable, storm shelter designation, and durable interior finish.

Fewer Trades & Faster Construction: Precast insulated wall panels are made off-site, reducing the need for multiple trades on-site, minimizing material waste, and accelerating project timelines. This approach requires less field labor and mitigates project risks, especially during adverse weather.
High Thermal Performance: Concrete’s thermal mass allows it to absorb and release heat gradually, reducing temperature swings inside the building. This energy efficiency supports lower heating and cooling costs and helps maintain a more stable indoor environment.
Built-In Fire Resistance: Concrete’s natural fire-resistant qualities allow precast panels to achieve up to 4-hour fire ratings, enhancing a building’s safety and meeting strict fire codes. This property adds critical protection for both occupants and structures.
Resilient & Durable: Precast concrete withstands a variety of environmental challenges, including impacts, high winds, and seismic events, offering a long-lasting, low-maintenance solution that ensures multi-hazard resilience.
Storm Shelter Designation: In certain regions, precast wall panels can qualify as community storm shelters, meeting safety standards for severe weather protection and providing reliable shelter options for vulnerable areas.
Durable Interior Finish: The interior side of precast panels is sturdy enough to serve as a finished surface, reducing the need for additional materials. This ready-to-use finish adds efficiency and an attractive look, streamlining a project’s final stages.

What are wythe connections?

A wythe is a continuous vertical segment of masonry that consists of a single unit in thickness. It can either stand independently or be interlocked with an adjacent wythe. Precast concrete sandwich panels are typically made of an outer and inner layer, or wythe, of concrete separated by the insulating material. Wythe connectors link two concrete wythes together and help keep a precast panel intact throughout transportation, handling, and servicing work.

What is thermal mass?

A key benefit of a concrete structure is thermal mass and its ability to absorb and release heat.

Concrete has a high specific heat, high density, and low conductivity; therefore, a large amount of heat energy can be absorbed with little change in temperature. The high thermal mass provides thermal storage, reducing daily and seasonal temperature swings, absorbing heat during the day in summer and cooling the building by storing heat from the sun over the surface of the building rather than allowing it to flow into the building. This cycle reverses at night, during the cooler time of the day, when heat is released back out into the atmosphere. By damping and shifting peak loads to a later time, thermal mass reduces peak energy requirements for building operations. As an added benefit, indoor temperature fluctuations are reduced and occupant comfort is enhanced. The required capacity of the mechanical equipment is also reduced, lowering initial costs as well as ongoing operating costs since smaller equipment running continuously uses less energy than large equipment running intermittently.

ASHRAE 90.1-2010 acknowledges the thermal mass benefits of concrete walls in specifying lower minimum insulation R-values and higher maximum wall U-factors for mass (concrete) wall construction in specific geographic areas. Thermal mass is not a total substitute for insulation. Although much of the heat stored in mass exterior walls is reradiated to the exterior of the building, some is also radiated to the interior. High performance precast concrete sandwich panels construction is an excellent way to combine mass and insulation in walls. The function of insulation is to form a zone with low thermal conductivity (high R-value) that slows transmission of heat energy through the building envelope. When used in the right combination, insulation and thermal mass, along with a building design that captures solar light and heat energy, can improve the thermal performance of buildings and lower overall energy requirements.

Also, smooth steel troweled interior concrete walls or ceilings can be painted or left bare to provide a clean, durable, and mold-resistant surface. Not only is less material used, but the exposed thermal mass elements can more readily absorb heat from interior spaces and later release heat in the evenings when buildings are not occupied.

For more details on the benefits of precast insulated wall panels, please download:

What R-value is possible with precast insulated wall panels?

A range of R-values can be obtained by varying the insulation thickness and material or, in some cases, by varying the unit weight of the concrete. The effects of thermal damping can vary with the climate and the building use. However, insulated precast concrete panels for walls will almost always provide both reductions and delays of the peak loads affecting a building. Therefore, even with equal R-values, a concrete sandwich wall will provide greater energy savings than a wall constructed of lightweight (low mass) materials. This effect is recognized by the major building codes and can be considered during the panel design.

PCI does not recommend one type of insulation over another, but rather it depends on a specific project, its use, location, R-value of different products in panel design, and other factors. Some considerations to keep in mind include:

If a project is being built in a very hot climate, then the maximum temperature may influence the choice, such as a POLYISO, which has a maximum temperature of 250 degrees.
If a project is being constructed in a moist environment with a lot of cycle wetting and drying, XPS may be more appropriate. XPS usually has about 1/10 of the moisture absorption. Moisture is a concern, since as materials absorb moisture, their resistance to heat flow decreases since moisture is a thermal conductor.
Note rigid foam insulation varies in R-value per inch.

The three main types of insulation used in the manufacture of precast concrete insulated wall panels are: expanded polystyrene or EPS, extruded polystyrene or XPS, and POLYISO. Recent climate changes regarding the compliance of these common rigid foam insulation products by county or state jurisdiction must be consulted as part of the selection and specification processes. Consult your local PCI-certified precaster regarding R-value requirements as well as panel design considerations for your next project.

How can I avoid thermal bowing when specifying insulated precast wall panels?

To minimize thermal bowing in precast insulated wall panels, consider the following strategies during the design and specification process:

Use Symmetrical Panel Design: Ensure that the thickness and type of concrete on both sides of the insulation layer are balanced. This symmetrical design can help reduce differential expansion and contraction, which leads to bowing.
Specify Low-Expansion Insulation Material: Choose an insulation material like extruded polystyrene (XPS) with a low thermal expansion coefficient to reduce the movement caused by temperature changes.
Allow for Movement: Use flexible connections or fasteners that allow minor movements without stressing the concrete panels. This helps prevent bowing by accommodating small expansions and contractions.
Use Proper Panel Sizing & Spacing: Choose shorter panel lengths, as longer panels are more susceptible to bowing due to temperature variations. Ensure adequate spacing between panels to allow for independent movement.
Design for Ventilation: Proper ventilation behind panels can help equalize temperatures across the panel, reducing the risk of differential heating that can cause bowing.
Include Joint Details for Expansion Control: Implement control joints or expansion joints at intervals within the panel layout. These joints accommodate thermal expansion and contraction without causing deformation.

What are the common types of precast insulated wall panels?

There are three options for considering insulated precast concrete sandwich panels and cladding. These types are composite, non-composite, and partially composite wall panels. Which type used is greatly dependent upon the use of cladding and how it is attached to the structure.

Non-Composite Panels: Cladding panels which are structurally secured to a building’s superstructure solely by attachments cast into a thick back wythe. An example is a 6” structural back section that contains all bearing and lateral connections as well as carries the weight of the entire panel along with any other materials (windows, metal panel, etc.) without the need of transfer through the insulation to engage concrete reinforcement of the exterior section. This method allows the two concrete wythes to act independently both structurally and limiting influence of thermal bowing.

Composite Panels: Cladding panels which are bearing to a foundation and support panels and/or other product above. The horizontal joints are grouted to transfer of loading evenly to the foundation. Panels are still connected to the superstructure for lateral support. Depending on the precast panel shapes, bearing panels onto columns are not always an option, and the use of composite action for panel stability may also need to be employed. By connecting the exterior and interior wythes of concrete with composite type connectors, thermal bowing occurs when temperature differences on interior and exterior surfaces cause expansion differences in the two sides.
Partially Composite Panels: Partially composite panels strike more of a balance by allowing some load transfer between the interior and exterior wythes without fully linking them. With selective connectors, these panels gain stability and reduce thermal bowing, as the wythes can move somewhat independently. This makes partially composite panels a practical choice when both thermal performance and structural support are priorities.

Want to work with precast concrete insulated wall panels in your upcoming projects? Explore helpful tools, detailed information on working with precast, and expert guidance to support your next project in our Solutions Center.

FAQ Fridays: Precast Insulated Wall Panels