Preventing Thermal Bridges in Buildings

Thermal bridges in buildings are most commonly described as the occurences of penetrations through the insulation plane by highly conductive materials, such as structural steel components.^[1] For those concerned with building energy performance, the reduction or elimination of thermal bridges can reduce the total energy used. What this means for the typical building/home owners, who are not typically concerned with the physics, is a reduction in monthly bills and more comfort for occupants(i.e. More comfort for less money).

The Problem[edit | edit source]

Thermal bridging has a dramatic impact on the energy performance of new airtight buildings, but should only be adressed after comlying with air tightness, ventalation, space conditioning and insulation requirements. Speaking in termas of R-value thermal bridging can range from anywhere from 10% to 50% for stud construction. In situations where thermal bridging is high it is important to reduce or eliminate conductive heat transfer through thermal bridges. This is typically done by the use of thermal isolation, contact area reduction, and proper material selection.

A Brief History[edit | edit source]

It was not until the latter part of the 20th century that energy efficiency became a major concern in the commercial and residention building industries. The 1970s energy crisis was the catylist that lead to the building energy efficiency experiment. The first step was the use of airtight construction, which after many moisture related failures lead to the incorporation of ventelation.^[2] In the following years other concerns, such as proper insulation and thermal bridging began to arise. The occurrence of thermal bridging in buildings has been recognized since the 1980s^[3],^[4] but at the time was not well known in the construction industry .^[3] In the mid-1980s, while Canada and Europe continued to fund building science (Building Physics in Europe)research, research in the United States was at a stand still .^[2] Europe's role at the forefront of building performance led to the introduction of the ISO 10211 standard, which addresses thermal bridges, in 1995. Since the mid 1990s, primarily brought on by the Energy Policy Act of 1992, the United States began to gain momentum in building performance. In North American standards thermal bridging has primarily been handeled by the American Society of heating, refridgeration, and air-conditioning Engineers (ASHRAE), but a document similar to ISO 10211 has yet to be produce. The advancement in computational modeling has produced software capable analyzing the heat transfer in building assemblies, which is a stong tool in the analysis and prevention of thermal bridges.

Who's to Blame[edit | edit source]

The truth is that everyone on the design team should be aware of thermal bridges. However, it has typically fallen to those whith an understanding of energy efficiency (e.g. architect, mechanical engineer, or enclosure specialist), however when it comes to structural thermal bridges it should be the responsibility of the structural engineer^[5] .^[6] Recognizing this structural engineers have recently joined the game, with the argument is that one would not want those untrained in structural engineering to impliment design changes.^[6]

Solutions[edit | edit source]

Thermal Isolation[edit | edit source]

Area Reduction[edit | edit source]

Material Selection[edit | edit source]

References[edit | edit source]