BREAKING THE BRIDGE

摘要

Not so long ago, in simpler times, thermal bridging was considered to be of limited importance and largely overlooked. Today, it sits alongside airtightness and insulation as a critical aspect of design and an essential element in delivering energy efficiency in all forms of construction. A thermal bridge, also known as a cold bridge, occurs within the building envelope where an area has significantly higher heat loss than the surrounding fabric, due to either geometry or the presence of materials with poor insulating properties. This creates a bridge for heat to escape, reducing energy efficiency. The resulting cold patch can also attract condensation, potentially leading in turn to a mould problem. Common examples of thermal bridges include lintels, balconies and the junction between floors and walls. These are referred to as "non-repeating" or "linear" thermal bridges, for which the specific heat loss should ideally be calculated and included in the overall loss from the building. There are also "repeating" thermal bridges - for example, those created by wall ties or the studs in timber frame construction. These are accounted for in the U-value for the wall, so don't require a separate thermal calculation.