A Superior Solution to Thermal Bridging


Preventing thermal bridging in a building's envelope requires continuous insulation and a weather-resistant barrier. Fox Blocks insulated concrete form (ICF) all-in- one wall system combines both of these elements, along with structure and attachments, which effectively stops thermal bridging.

What is Thermal Bridging?

A break or penetration in the building envelope creates a thermal bridge. The building's envelope provides the thermal barrier that controls the flow of heat, moisture, and air between the exterior and interior of the building or home. Any defects or openings in the envelope allows moisture and air to infiltrate a wall system. Common areas in the envelope where thermal bridges occur include the junctions between the wall, floor, or roof, near windows and doors, by studs, and around holes for cables and pipes.

Thermal bridges lower a building's effective R (resistance)-value, which diminishes the energy-efficiency of the home or building, along with the comfort of the occupants. The R-value represents the insulation's capacity to resist heat flow — the higher the R-factor, the better the insulation's thermal resistance. The effective R-value includes all the construction products: insulation, siding, studs, plywood, drywall, etc.

Thermal bridges also increase the level of condensation within the wall assembly.

Condensation happens when the temperature inside the wall system drops below the dew point - the temperature when the water in the air condenses into a liquid. The more air (and the moisture associated with it) that infiltrates a wall system by thermal bridging, the more condensation can occur - which will result in excessive moisture accumulation within the wall assembly. Moisture in the wall system degrades the thermal resistance of the cavity insulation and leads to the growth of mold and rot. Mold diminishes the indoor air quality (IAQ) in a home or building, and rot destroys the integrity of a structure.

How to Prevent Thermal Bridging

Preventing thermal bridging in the building envelope, to maintain the effective R-value and stop condensation, requires applications of continuous insulation (CI) and air/vapor barriers.

Continuous Insulation

Correctly applied CI prevents thermal bridging by producing a tight building envelope. Notably, the ASHRAE 90.1 and 2018 IECC requires CI. The ASHRAE Standard 90.1-2013 defines CI as continuous insulation across all structural members (including the walls, roofing, foundations, windows, and doors) without thermal bridges other than fasteners and service openings. The standard and the home’s or building’s climate zone mandate the quantity of insulation (as indicated by the R-value) to achieve CI and stop thermal bridging.

Air and Vapor Barriers

Preventing air and moisture infiltration through thermal bridges, along with moisture accumulation within the wall system, requires an application of a continuous air barrier and vapor barrier to the building envelope.

  • Building envelopes must be protected with a vapor barrier to prevent air and moisture infiltration into the wall cavity by thermal convection. Thermal convection happens when heat moves by the flow of air or liquid molecules from the warmer to the colder side of a wall, by way of a thermal bridge. Uncontrolled thermal convection causes drafty buildings and homes.
  • Moisture can infiltrate even the tightest building envelope. Therefore, to prevent moisture from accumulating, the wall system must include a vapor-permeable WRB. A vapor-permeable WRB allows moisture in the wall system to escape.

Fox Blocks Insulated Concrete Forms Stop Thermal Bridging

The Fox Blocks ICF wall system, with built-in CI and moisture and air barriers, stops thermal bridging. Easy to install and code-compliant Fox Blocks also provide good IEQ and will maintain the full effective R-value for the life of the building without the concern of mold, mildew or rot.

Fox Blocks prevent thermal bridges by creating airtight building envelopes with superior moisture resistance. The high thermal mass of Fox Blocks ICFs provides CI with an R-value of 23. Fox Blocks’ solid continuous monolithic concrete wall also provides a tested and proven permeance rating below1.0.

Along with preventing thermal bridges, Fox Blocks offer other essential features:

  • All-in-one wall assembly combines five steps into one, structure, vapor retarder, insulation, air barrier, and attachment - a feature that hastens the project delivery by eliminating the need to coordinate specific trades
  • An interior and exterior wall system with high sound reduction, that achieves a high ASTM E90 Sound Transmission Classification (STC) rating of more than 50.
  • Non-toxic, containing little to no VOC.
  • Lacks organic material, so it resists pests like termites. Fox Blocks recommends Polyguard Products, Inc. 650 XTM or 650 XTP membranes, to ensure protection against termites
  • Resists winds of over 200 MPH, and projectile debris traveling over 100 MPH - particularly crucial in tornado and hurricane areas.
  • Provides superior passive firewall protection.

Please contact Fox Blocks professionals for more tips on how to prevent thermal bridging.