You may have heard the term thermal bridging before, but do you know what it means? In the same way a bridge gives people easy access across a waterway, a thermal bridge gives energy an easy path to travel through a building envelope.
What is Thermal Bridging?
It is said that the building envelope has one of the most important jobs within a structure. One of the primary goals of a building envelope is to separate two environments, the conditioned interior and un-conditioned exterior. A building envelope consists of several layers of materials that offer support and climate control. Securing and attaching all the building envelope layers is just as necessary as the materials themselves. Controlling thermal energy and moisture through the building envelope plays a significant role in a successful and effective structure.
To maintain the temperature of an interior space, it is essential to use a best practice continuous insulation (CI) system to slow down the temperature flow into or out of the building. Continuous insulation systems are good at their job, but best practices must be followed when it comes to fasteners and sub-framing materials. If the proper components and materials are not used, these areas can be prone to thermal bridges.
Thermal bridging can occur when highly conductive materials create a passageway allowing thermal energy or moisture to travel through the layers of building envelope material. An example may be using a metal screw with metal sub-framing on a building with metal studs. As the metal screws cool down due to exposure to cold air outside, that cool energy can travel through the connected metal building envelope components. When this cold exterior energy travels through the thermal bridge within the building envelope and is met with warmer interior energy, an exchange occurs. Condensation can them form at the point in which the exchange of hot and cold energy occurs. As condensation collects, a drop of water forms within the building envelope. One drop of water may seem like no big deal, but severe damage can result if this occurs over time.
Thermal bridging and the moisture issues it can cause have detrimental effects on the building’s life expectancy and the overall health of its occupants. To make matters worse, these issues can develop long before they become visible in some cases.
Common Effects of Thermal Bridging:
- Reduced Building Envelope Effectiveness – If passageways are created within the building envelope, it’s effectiveness in separating two environments decreases.
- Increased Energy Loss and Costs – If thermal bridging occurs within a building envelope, energy can easily escape or enter a building. The energy you are consuming to either heat or cool your building is wasted when this happens. In the end, you will expel more energy, thus increasing your operating costs.
- Increased Risk of Moisture Damage – If energy can travel through a building envelope due to thermal bridging, moisture can too. So whether it is water, condensation, or vapor, thermal bridges are a highway for moisture.
- Decreased Life Expectancy of Building – Moisture can build up within your building envelope, forming mold or mildew before you may be able to even see it. As a result, your building will likely have a decreased life expectancy and may need to be repaired or replaced sooner if this occurs.
- Increased Risk of Negative Effects on Occupant Health – If mold or mildew occurs, occupants may be at a health risk and at risk of occupying a building with unidentified structural issues.
- Increased in Building Material Waste Sent to Landfills – If buildings need to be replaced or repaired more frequently due to thermal bridging and moisture damage, more building material waste gets sent to landfills over time.
- Decreased Comfort of Interior Space – Controlling a building’s conditioned interior climate becomes increasingly tricky. If thermal energy from the unconditioned exterior can easily pass through the building envelope, this results in a more uncomfortable internal environment.
How Can Sub-Framing Material Affect Thermal Bridging?
Preventing thermal bridging within your building envelope is vital in avoiding the common building envelope issues listed above. So, how do you prevent thermal bridging? To stop a thermal bridge, you need a thermal break. A thermal break is a barrier that blocks energy flow. Incorporating materials and components with thermal breaks and low conductivity within your building envelope can make or break the success or effectiveness of your structure.
Thermal Bridging (Metal) Thermal Break (GreenGirt CMH)
Standard Metal Z-Girt Sub-Framing
There are two common types of material used for continuous insulation system sub-framing. These two materials are metal or fiber-reinforced polymer (FRP). Figure 1.1 below shows a standard metal sub-framing z-girt with a steady and highly conductive pathway for thermal energy or moisture to travel from the exterior cladding through a metal fastener, metal z-girt, and metal framing. This continuous insulation system is highly conductive, as the system components consist of all metal materials.
Standard FRP Z-Girt Sub-Framing
Another common continuous insulation sub-framing material is fiber-reinforced polymer (FRP). FRP continuous insulation sub-framing is demonstrated in Figure 1.2 below. Although thermal bridging is eliminated with the FRP sub-framing, the FRP material does not offer the same structural benefits as metal.
GreenGirt® Composite Metal Hybrid (CMH™) Z-Girt Sub-Framing
Advanced Architectural Products, creators of GreenGirt Composite Metal Hybrid (CMH™) z-girt sub-framing, has the best practice, thermally-broken, continuous insulation solution for your building envelope. GreenGirt® CMH™ material consists of a combination of fiber-reinforced polymer (FRP) paired with metal fastener retention plates. GreenGirt® CMH™ offers a complete thermal break with the use of FRP without compromising the structural strength of metal.
Figure 1.3 below demonstrates how the FRP component of GreenGirt CMH breaks the passageway for energy to travel through conductive components, while offering a structurally sound surface for fastener attachment and retention. Advanced Architectural Products offers a variety of SMARTci™ continuous insulation systems to fit your project’s specific needs. All SMARTci systems include GreenGirt CMH sub-framing, making SMARTci + GreenGirt CMH the overall, best practice continuous insulation solution for your building envelope.
Utilizing GreenGirt Composite Metal Hybrid (CMH) Z-Girt Sub-Framing:
- Eliminates thermal bridging
- Increases your building envelope effectiveness
- Decreases thermal energy loss and operating costs
- Decreases the risk of moisture damage
- Increases the lifespan of your building
- Decreases the amount of building material waste sent to landfills
- Decreases occupant health risk
- Increases the comfort of the interior environment
Download our Structural Engineering Study on GreenGirt® Composite Metal Hybrid (CMH™) vs. Generic FRP
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