Thermal Bridge-Free Insulation in Construction Building
The thermal performance of a building’s envelope can be greatly affected by thermal bridging, or localized areas of high heat flow through walls, roofs and other insulated building envelope components. Additional heat flow due to thermal bridging at interface details, such as shelf angles or the interface between windows and walls, can add up to be a significant portion of the heat flow through the building.
If major thermal bridges are not addressed adding insulation to building envelope assemblies may not provide significant benefits.
With the Building Envelope Thermal Bridging (BETB) Guide, Morrison Hershfield and project sponsors ultimately seek to facilitate the design and construction of more thermally efficient building envelopes. The guide serves as a valuable reference tool. It contains essential information for evaluating building envelope thermal performance, including easy-to-use methods for understanding, accurately calculating and mitigating thermal bridging.
What is Thermal Bridging
Also called a heat bridge or a cold bridge, thermal bridging occurs in the building envelope when a material component transfers heat through itself at a greater rate than surrounding components.
Thermal bridging at interface details, such as slabs, parapets and glazing transitions, can be sources of significant heat flow through the building envelope.
This transferring of heat through the envelope of the building results in energy reduction as heat flows through the thermal barrier.
Due to differing material components and envelope designs, adding more insulation will not necessarily decrease the energy use of the building, as many thermal bridging leads to heat flow bypassing insulation through these components.
Mitigating the impact of thermal bridging in the design of the envelope can therefore greatly impact energy and cost savings of the building, an increasingly essential consideration as the engineering and construction industries are tasked with designing and erecting buildings that consume less energy.
Key Components of Thermal Bridging
There are three components of heat loss: clear wall, linear and point.
Clear wall heat loss refers to the heat loss associated with the assembly, away from transitions and interfaces with major components.
The linear heat loss elements are interface details whose additional heat losses have been quantified per unit length. This includes elements such as slabs, parapets, corners, glazing transitions, etc.
Point transmittances are interface details whose additional heat losses have been quantified per occurrence, such as a beam or mechanical penetration.
What is a Thermal Break?
A thermal break is a non-conductive material that interrupts the conductive heat flow path. Proper design placement of thermal breaks aids in reducing heat loss through the building envelope.
Proper detailing at transitions between systems to ensure thermal breaks have been incorporated is important for mitigating thermal bridging.
Glazing systems can be designed as thermally broken with the addition of properly placed insulation within the assembly, preventing heat flow from traveling from the interior to the exterior and vice versa.