Recent Trends and Development in Construction

civil 

Recent Trends and Development in Construction

THERMAL BRIDGING

INTRODUCTION


Thermal bridging occurs in building envelopes when materials with high thermal conductivity, such as steel, timber and concrete create pathways for heat loss that bypass thermal insulation. When these poor insulating materials provide an uninterrupted “short circuit” between the interior and exterior of a building, the thermal bridge can result in

a) Accelerated heat loss through that area,

b) Localized cold spots on the interior of a wall that may cause a risk of condensation.


This effect is most significant in cold climates during the winter when there is a great differencein the indoor-outdoor temperature. Thermal bridging can also occur in building envelopes when there are gaps or breaks in the insulation envelope prevail. The reduced or missing insulation allows warm air that makes contact with cold external surfaces. It accelerates heat loss through the area and localizes cold spots on the interior.

Thermal bridging must be considered if there is more than one possible heat flow path through that surface. If the thermal bridge allows two or more possible heat flow paths, in the main body of the floor, wall, roof. etc. then its effect must be considered.

Typically, construction details are broken down into two parts when considering thermal bridging:

Part 1. When the thermal bridge is part of the main structure of the floor, wall, roof, etc., the effect of the thermal bridge is included in the calculation of the U-value for that element.

Part 2. The thermal bridge occurs around doors, windows and other penetrations of the insulation envelope. These are typically grouped together as one major contributor to heat loss from the building.

thermal-perf-cw-panel


THERMAL BRIDGING IN CONSTRUCTION


Thermal bridging is a layer of the building enclosure system that resists heat flow between the interior conditioned environment and the exterior unconditioned environment.This method is used frequently with reference to a building’s thermal envelope. Heat will transfer through a building’s thermal envelope at different rates depending on the materials present throughout the envelope. Heat transfer will be greater at thermal bridge locations than the area of insulation because there is less thermal resistance. In the winter, when exterior temperature is typically lower than interior temperature, heat flows outward and will flow at greater rates through thermal bridges.

At a thermal bridge location, the surface temperature inside the building envelope will be lower than the surrounding area. In the summer, when the exterior temperature is typically higher than the interior temperature, heat flows inward at greater rates through thermal bridges. This causes winter heat losses and summer heat gains for conditioned spaces in buildings.

Despite insulation requirements specified by various national regulations, thermal bridging in a building's envelope remains a weak spot in the construction industry. Moreover, in many countries, building design practices implement partial insulation measurements that are foreseen by regulations. As a result, thermal losses are greater in practice that is anticipated during the design stage.