Thermal Bridging and How to Reduce It

By Tobias Roberts Rise Writer

Jun 23, 2021

If you have ever done an energy audit on your house, the chances are that the home energy consultant mentioned the word thermal bridging at least a few times. Even if you didn't quite understand what the consultant was talking about, you probably got the idea that thermal bridging does not improve your home's energy efficiency. This short article explains what thermal bridging is, why and where it commonly occurs in homes and strategies that every homeowner can implement to reduce this problem.

What Is Thermal Bridging?
Where Does Thermal Bridging Occur?
Thermal Bridging in New Home Construction
How Can You Prevent Thermal Bridging in New Home Construction?
What About Thermal Bridging in Existing Homes?
How Do You Reduce Thermal Bridging in Existing Homes?

What Is Thermal Bridging?

Thermal bridging occurs when heat passes through a material that is more conductive than the materials around it. This heat loss travels from the inside to the outside of a building in cold weather. In reverse, heat gain occurs from outside to the interior of a home during hot summer days. For example, wood or steel beams with cavity insulation will create a pathway for heat loss or heat gain. This unwanted transfer of energy causes significant reductions in energy efficiency in homes, driving up energy bills.

The movement and transfer of heat can be tricky to understand. However, most homeowners comprehend that reducing unwanted heat loss and heat gain is a fundamental aspect of reducing energy bills. Builders, energy auditors, and others in the sustainable building industry focus on high-performance insulation and airtight building envelopes as the two most essential factors in optimizing a home's energy efficiency and thermal performance. Though both of these elements certainly play an indispensable role, thermal bridging can drastically reduce a homeowner's investment in high-performance insulation.

A thermal bridge acts as penetration into the insulation layer with a highly conductive material. This transfer usually occurs in your home's walls and roofs. However, we explain in more detail below where exactly thermal bridging can and does frequently happen. These highly conductive materials placed within your insulation cavities allow for an increased rate of heat flow through the insulating material.

Why Does Thermal Bridging Matter?

Essentially, conductive materials worsen the insulating properties of your fiberglass batts, closed-cell spray foam, sheep wool batts, or whatever other types of insulation your house uses. Higher energy bills and colder or hotter areas lead to reduced comfort levels inside the home. In some cases, thermal bridges may even compromise your building's integrity.

A thermal bridge might be compared to a sturdy fence that a homeowner builds, intending to keep their pet inside the yard. Even if the fence was constructed with the sturdiest and most durable materials, one loose fencing panel could allow your furry friend to escape into the street.

The conductive material located around your home's insulation creates a path of least resistance for heat transfer. This doesn't render completely inept the R-value of your home's walls, ceilings, foundation, or attic. But, a thermal bridge does give rise to a general drop in the R-value and thermal resistance of your home.

A thermal bridge in a building or home may also lead to mold growth that could negatively affect your indoor air quality and the structural integrity of your house. The heat transfer through thermal bridges often leads to condensation or moisture building up within the building envelope. This thermal bridging not only results in thermal discomfort but also can quickly lead to mold and mildew growth.

Where Does Thermal Bridging Occur?

Thermal bridges occur where highly conductive materials penetrate the insulation around your home. Thermal bridges are worse when the highly conductive materials form a continuous interruption of the insulation from the exterior to the interior.

The framing of your home is the most common source of thermal bridging. A 2x6 or 2x8 stud in your wall will provide that dreaded "path of least resistance" for heat transfer to occur. Besides wooden or metal studs in your walls, thermal bridges tend to occur most commonly at the junctions between two or more building elements in your building envelope. Some of the most common areas for serious thermal bridging include:

Floor-to-wall or balcony-to-wall junctions
Roof/Ceiling-to-wall junctions
Window-to-wall junctions
Door-to-wall junctions
Wall-to-wall junctions
Wood, steel, or concrete studs and joists built into an exterior wall, ceiling, or roof construction
Recessed lights that penetrate insulated ceilings
Window frames and door frames
Metal ties in masonry cavity walls

It is also important to mention that the level of thermal bridging is also impacted by the type of material used.

What Building Materials Transfer the Most Heat?

Metal is much more conductive of heat than wood. Galvanized steel studs in your walls will thus lead to much more unwanted heat transfer. However, as the price of lumber in North America continues to skyrocket, many builders turn to steel and metal.

Though contractors might market steel framing as superior in strength and durability, there are a few downsides that need to be taken into consideration. Steel components for structural framing will have a much higher embodied energy footprint than their wooden or lumber counterparts. Nor can steel building elements be able to capture or sequester carbon as can wood. If not thermally broken (eliminated thermal bridge), steel structural components risk increasing thermal bridging in your walls, roof, and foundation.

Though your home builder or contractor might tell you that your walls have achieved an R-19 insulation rating, these ratings rarely consider the thermal bridging that occurs through the house frame. In most cases, a structure that was framed with wood 2x6s placed 16 to 24 inches apart might only have a total R-value of R-13. For metal-framed homes, that insulation rating is most likely significantly lower.

Thermal Bridging in New Home Construction

Okay, by now, you should be convinced that thermal bridging presents a sizeable problem for your home's energy efficiency and thermal performance. But does his mean that you essentially have to choose between the structural integrity of your home and maximizing energy efficiency? The structural elements and framework of a house are certainly the primary cause of thermal bridges that result in high heat loss and low surface temperatures in a room. Fortunately, innovative building techniques can allow you to essentially stop thermal bridging from occurring within and around your home's structural elements.

How Can You Prevent Thermal Bridging in New Home Construction?

In new home construction, the following building strategies can help to reduce thermal bridging drastically:

Add continuous rigid insulation to the exterior of your home.
Build with SIPs (structural insulated panels).
Use advanced framing techniques.
Apply strips of insulation directly on top of the wood studs.
Add insulation on the exterior of the basement walls.

Continuous Exterior Insulation

On the exterior side of your structural studs, continuous insulation - also sometimes known as "outsulation" - will form a tight building envelope over your home. This continuous layer of insulation will break the path of least resistance that occurs with thermal bridging. Rigid insulation panels placed under your exterior cladding offer an easy way to cut back on thermal bridging. Homeowners can choose from expanded polystyrene (EPS), extruded polystyrene (XPS), graphite polystyrene (GPS), and mineral wool rigid insulation, to name just a few products.

Build with SIPs (Structural Insulated Panels)

Another way to cut back on thermal bridging is to build with structural insulated panels. SIP assembly works together as an engineered system to provide insulation and structural integrity for your home, drastically reducing the need for studs that penetrate your insulation barrier. SIPs made from graphite polystyrene offer more than 20 percent higher R-value than many alternative SIPs. They can be manufactured using post-consumer or post-industrial recycled content.

Advanced Framing Techniques

Today, many builders are using advanced framing techniques that attempt to reduce the amount of lumber used to construct a wood-framed house. According to the ENERGY STAR Program, "advanced framing improves energy efficiency by replacing lumber with insulation material. The whole-wall R-value is improved by reducing thermal bridging through the framing and maximizing the wall area that is insulated."

Insulation on Wood Studs

Recently, some builders have been experimenting with a new approach that involves applying strips of insulation over wood studs. This step is most likely the least expensive way to limit thermal bridging as the small insulation strips provide a thermal break. Another innovative take on this has been the production of insulated studs by the company Tstud, which create an effective thermal break.

Insulation Outside Basement Walls

This technique also helps to lower thermal bridging and reduce foundation heat loss.

What About Thermal Bridging in Existing Homes?

Unfortunately, thermal bridging was largely ignored by home builders for much of the past century. This neglect leads to higher energy bills, more uncomfortable home interiors, and even issues with mold growth in interior walls. Luckily, every homeowner can do a few simple renovation techniques to limit thermal bridging in an existing home.

How Do You Reduce Thermal Bridging in Existing Homes?

Providing a layer of continuous insulation on either the interior or exterior wall is the best way to stop thermal bridging from occurring. For existing homes, adding continuous insulation from the interior generally requires a complete remodel as you would be forced to remove and remodel drywall, trim, or other interior finishes.

However, adding that needed layer of continuous insulation from the outside is relatively easy, especially if you are planning to renovate the exterior cladding of your house. When you install new siding, it offers a perfect opportunity to add continuous rigid board insulation underneath.

Thermal bridging has most likely cost you hundreds, if not thousands, of dollars in higher energy bills in the past. Fortunately, improved building techniques for both new builds and remodels offer a relatively straightforward path to eliminating this pesky problem.

Disclaimer: This article does not constitute a product endorsement however Rise does reserve the right to recommend relevant products based on the articles content to provide a more comprehensive experience for the reader.Last Modified: 2021-06-23T19:16:15+0000

Article by:

Tobias Roberts

Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.