Building Science

What Is Thermal Bridging & How to Reduce It?

The exterior wall of a building is the barrier that keeps tem­per­a­ture, moisture, wind, and pollution outside and creates a com­fort­able and healthy indoor envi­ron­ment. A primary goal of con­trac­tors and archi­tects is to design a wall assembly with a thermal barrier that resists heat transfer between the inside and outside. Thereby the interior of a building stays warm in cold winter months and cool in the summer. A build­ing’s wall assembly resis­tance to this flow is measured by its effective R‑value. The effective R‑value includes all the materials used in its con­struc­tion: the drywall, studs, fiber­glass batts, plywood or OSB sheathing, water control plane, and siding. The larger the R‑value, the lower the con­duc­tiv­i­ties of the wall assembly. Problems in a wall’s assembly, such as thermal bridging, increase the wall’s con­duc­tiv­i­ty, which leads to increased air flow through between the interior and exterior of the building. Building exterior walls with low con­duc­tiv­i­ty and high effective R‑values will keep unwanted outdoor elements outside and ensure a com­fort­able indoor environment.

What is Thermal Bridging?

A thermal bridge is a more con­duc­tive area of a wall assembly, compared to the sur­round­ing space, like the stud space and the exterior insu­la­tion. Heat and energy flow through the thermal bridge at a higher rate than the sur­round­ing areas; which reduces the effective R‑value of the wall assembly. Thermal bridging typically occurs near highly con­duc­tive materials like wood studs, metal studs, steel, and concrete. For example, wood studs allow heat to flow through the wall at a rate that is three times faster than the heat flow through the insu­la­tion. So, even though the insu­la­tion has a nominal R‑value of 19, the building’s effective R‑value is lower. Steel framing is even more con­duc­tive than wood. In fact, steel framing typically reduces the sur­round­ing insu­la­tion’s R‑value by as much as 50%, while wood framing reduces the sur­round­ing insu­la­tion’s R‑value by less than 10%. Deter­min­ing and pre­vent­ing potential thermal bridges within a wall assembly is essential for con­struct­ing a com­fort­able and energy effi­cien­cy building.

How to Reduce Thermal Bridging

Wrapping a building’s envelope with a layer of con­tin­u­ous insu­la­tion cuts off thermal bridging. Stopping thermal bridging saves energy and lowers the risk of mold and rot by elim­i­nat­ing or reducing con­den­sa­tion. Con­tin­u­ous insu­la­tion is installed on the exterior of all areas of the building envelope except openings for windows, skylights, doors, and building service systems. Con­tin­u­ous insu­la­tion is required by ASHRAE 90.1 and 2015 IECC. ASHRAE 90.1 is the U.S. energy standard for all com­mer­cial and res­i­den­tial single or multi‐​family struc­tures greater than three stories in height above grade.The standard defines con­tin­u­ous insu­la­tion as insu­la­tion that is con­tin­u­ous across all struc­tur­al members without thermal bridges other than fasteners and service openings.The amount of insu­la­tion required (as indicated by the R‑value) by the standard depends upon its climate zone. Con­tin­u­ous insu­la­tion complies with building codes, elim­i­nates thermal bridging and increases the effective R‑value in a wall assembly.

Bautex Block Continuous Insulated Wall System

The Bautex Wall System con­tin­u­ous insu­la­tion stops thermal bridging and exceeds the energy effi­cien­cy require­ments of the most strict building codes. The R‑value for Bautex Blocks is R‑14, without exterior or interior finishes. A building with Bautex Block con­tin­u­ous insu­la­tion with brick veneer is an R‑18 system; far exceeding ASHRAE 90.1 rec­om­men­da­tions. In warmer, southern climate zones, ASHRAE 90.1 minimum R‑value require­ments for con­tin­u­ous insu­la­tion (above grade, mass walls), are less than R‑8. The Bautex Block is also fire-rated, noise-reducing, storm-resistant and easy to install. Interior and exterior walls of res­i­den­tial and com­mer­cial buildings can utilize Bautex Walls. The use of Bautex Wall System con­tin­u­ous insu­la­tion, stops thermal bridging, improves energy effi­cien­cy and saves building owners money for years to come.

Other Sources of Thermal Bridging — the Window and Doors

Thermal bridging also occurs through windows and doors. The addition of insulated shades and storm doors can reduce the thermal bridging through these openings. 

Thermal bridging occurs in buildings near highly con­duc­tive, low R‑value materials like wood studs, steel, and concrete. These highly con­duc­tive materials allow heat to transfer through the thermal barrier, usually the exterior wall. A proven method for elim­i­nat­ing thermal bridging is con­tin­u­ous insu­la­tion. Con­tin­u­ous insu­la­tion covers all parts of a building, elim­i­nat­ing thermal bridges other than those caused by fasteners, windows, doors, and skylights. Bautex Block is an excellent choice for con­tin­u­ous insu­la­tion. Bautex System’s light­weight stay-in-place insulated concrete block is a highly per­form­ing, strong, and simple-to-install wall system, with an R‑value far exceeding industry rec­om­men­da­tions. The Bautex Block gives con­trac­tors and archi­tects an efficient method to eliminate thermal bridging; reducing energy loss and ensuring savings for owners of both res­i­den­tial and com­mer­cial buildings.