Eliminating Thermal Bridging in Precast Sandwich Panels

Thermal bridging in a precast sandwich panel almost never comes from the insulation itself. It comes from whatever holds the two concrete layers together. Solid concrete ribs and steel connectors conduct heat straight through the insulation layer, so eliminating the bridge means changing the connector, not the insulation.

What Actually Causes Thermal Bridging in a Sandwich Panel

A precast sandwich panel is three layers: an exterior concrete wythe, a layer of rigid insulation, and an interior concrete wythe. Wythe connectors run through the insulation to hold the two concrete layers together and, depending on the design, to transfer structural load between them.

That’s where the problem starts. Any connector made of a material that conducts heat, steel trusses, or a solid concrete rib poured straight through the insulation to tie both wythes together, gives heat a direct path from the exterior wythe to the interior one. The insulation layer can be rated at a high R-value on paper and still perform far worse in the finished wall, because the connectors and any solid concrete zones at edges or openings are doing an end-run around it.

This is exactly why ASHRAE 90.1 doesn’t let a designer use the insulation’s rated R-value alone for a precast wall. Insulated precast panels are classified as mass walls under ASHRAE 90.1 Appendix A, and the prescriptive path requires either a minimum insulation R-value with defined connector limits, or a full U-factor calculation for the assembly that accounts for thermal bridges, not just the clear-field insulation.

Composite, Non-Composite, or Partially Composite: The Real Trade-off

Connector choice comes down to three approaches, and each one trades structural performance against thermal performance.

For most building envelope applications, including data centers, partially composite is the practical middle ground: meaningfully better thermal performance than a steel or solid-concrete composite panel, without giving up as much structural capacity as a fully non-composite design (see how each connector type performs).

Four Things That Actually Eliminate Thermal Bridging

• Low-conductivity connectors. Swapping steel trusses or solid concrete ribs for GFRP or fiberglass connectors is the single biggest lever available. This is the decision that determines whether the connectors themselves become a thermal bridge, more than any other spec on the panel.
• Continuous, edge-to-edge insulation. Solid concrete “short circuits” at panel edges, window and door openings, and connections into foundations or floor slabs undo the benefit of a good connector choice. Insulation needs to run edge-to-edge with as few solid concrete penetrations as possible.
• Insulation type matched to the application. EPS, XPS, and polyiso each perform differently. XPS resists moisture absorption better in wet climates, polyiso holds up to higher temperatures, roughly 250°F, in hot climates, and local codes increasingly restrict certain foam products outright (see PCI-MA’s comparison of insulation options).
• Joint and connection detailing between panels. The connector inside the panel isn’t the only place heat can cross. Where one panel meets the next, and where panels tie into the structure, needs its own thermal break and sealant detailing, or the joint becomes the next bridge after the connector problem is solved.

Why This Matters More in a Data Center Specifically

Two things make thermal bridging a bigger deal on a data center envelope than on a typical commercial building.

First, a thermal bridge creates a cold spot on the interior wall surface. In most buildings, that’s an energy efficiency issue. Next to electrical switchgear, cable pathways, or IT equipment, a cold spot is also a condensation risk, and moisture near electrical equipment is not a minor problem.

Second, ASHRAE 90.1’s mass wall U-factor requirement affects the cooling load at the building perimeter, which feeds directly into the facility’s overall power usage effectiveness. Data center owners already track PUE closely, and a wall assembly that underperforms its rated insulation because of connector bridging is a quiet, permanent drag on that number.

Get the Connector and Insulation Strategy Engineered Before Drawings Lock

Connector type, insulation continuity, and panel joint detailing all need to be settled before a precast wall panel goes into production, not adjusted after. Locke’s in-house engineering team, PE-stamped in five states, works through this as part of Locke’s custom engineered precast solutions, rather than defaulting to a standard panel design that wasn’t built for your specific envelope requirements. Talk to Locke’s engineers about your wall assembly before your design is finalized. When the connector, insulation, and joint detailing are locked, submit your drawings to move into production, and see the full range of precast solutions for data centers Locke manufactures, including its NPCA-certified plant and quality control program.

Frequently Asked Questions

What actually causes thermal bridging in a precast sandwich panel?

The wythe connectors, not the insulation. Steel trusses and solid concrete ribs that tie the two concrete layers together give heat a direct conductive path through the insulation layer.

Do steel connectors ruin the thermal performance of a sandwich panel?

They significantly reduce it. A fully composite panel using steel or solid concrete connectors gives the best structural performance but the worst thermal performance of the three connector approaches, because the connector itself becomes the bridge.

What’s the difference between composite and non-composite sandwich panels?

Composite panels use conductive connectors to transfer structural load fully between wythes, maximizing strength but creating thermal bridges. Non-composite panels use low-conductivity pin connectors that don’t transfer load, maximizing thermal performance but leaving the exterior wythe non-structural. Partially composite panels, often using GFRP connectors, sit between the two.

Why does thermal bridging matter more in a data center wall than in a typical building?

A thermal bridge creates a cold spot on the interior wall surface, which is a condensation risk near electrical and IT equipment specifically, not just an energy efficiency issue. It also affects the building’s U-factor compliance under ASHRAE 90.1, which feeds into the facility’s overall power usage effectiveness.