Many have met the concept of a cold bridge in literature and articles related to construction, but the essence of this phenomenon often remains unclear. Today we will take a closer look at this topic and explain what the emergence of cold bridges is fraught with, and also give the most typical examples..
Basic concepts of heat engineering
The temperature of all objects in the world around us is characterized by the intensity of vibrations of atoms: the more excited they are, the hotter the body in question. However, elementary particles cannot conserve their energy forever, they dissipate it, colliding with neighboring atoms and molecules. Because of this, two bodies with the same temperature, placed in an isolated environment, will gradually acquire the same degree of heating, in the same way, a heated house in winter will completely cool down over time..
To slow down the cooling of the house, construction technologies provide for a number of measures to improve thermal protection. First of all, a device is used for an outer shell made of materials that do not transmit heat well: mineral wool, aerated concrete, foamed polymers and the like. The essence of the action of thermal protection lies in the fact that all materials used have porosity, due to which the length of the route that thermal energy is forced to pass along the way to the external environment significantly increases. The efficiency with which various materials contain heat is called heat transfer resistance..
The very principle of thermal insulation has been known for a long time; previously, natural materials were used for these purposes: moss, sawdust, straw, crushed peat. The current materials are more effective, but the specifics of their use are such that in most cases it is necessary to use mechanical fasteners made of dense and therefore heat-conducting materials. In addition, the design of many buildings requires the use of reinforcing elements, such as lintels over openings or posts of frame walls. Their resistance to heat transfer is lower, due to which the overall efficiency of thermal protection decreases..
Consequences of a temperature bridge
Despite the fact that the share of temperature bridges in the total cross-section of the enclosing structures is small, they have an extremely negative effect on the energy efficiency of the building and provoke a number of related problems. First of all, you need to understand that the cold bridge never contributes to the increased heat outflow in a point, it also cools the adjacent area, often quite strongly. Because of this, the intensity of the heat flux increases markedly..
Another negative effect of the appearance of gaps in thermal protection is the cooling of sections of internal walls or hidden elements to the temperature at which condensation falls on them. This is extremely bad for the durability of building structures and, among other things, can cause the formation of mold and mildew, dangerous to health..
Examples and remedies
The most common example of a cold bridge is a nail driven into wood. In a frame house, where metal fasteners are used everywhere, such point heat leaks reduce the already low resistance to heat transfer, due to which the frame racks are greatly overcooled, which is clearly visible during thermal imaging. There are several solutions to this problem: use self-tapping screws that provide sufficient fastening reliability at a shallow screw-in depth, or make the frame two-row and shift the racks.
Heat distribution in the thickness of the wall with metal fasteners (left) and through floor slabs (right)
Another example is concrete lintels for reinforcing openings and ends of monolithic floors. The cross section of these elements is large enough, which leads to a very significant increase in heat loss. To block the outflow of heat, barriers made of synthetic insulation are used to act as a thermal break. During pouring, partitions made of expanded polystyrene are inserted into the concrete lintels, and the ends of the floors are shifted into the section of the walls and surround them along the perimeter with a belt of reinforced thermal protection. Both of these principles – breaking the heat flux and enhancing thermal protection along the circuit – are the main ways to counteract extensive cold bridges..