The energy needs of a house are essentially determined by the tightness and homogeneity of the building envelope. The weak points of the external covering, i.e. thermal bridges, allow heat to escape towards the outside and cold to penetrate into the rooms. This costs energy and can lead to mold and structural damage due to condensation. Where do these thermal bridges form and how can they be avoided? We give the answer below:
CAUSES OF THERMAL BRIDGES
Thermal bridges are thermal weak points in the building envelope through which energy is lost and cold can penetrate from the outside. This is why they are commonly called cold bridges. Thermal bridges mainly occur at component connections and connection points, i.e. in the area of windows and doors, in corners of the house or on the roof.
Basically, four different causes of thermal bridges can be distinguished, although they can also occur due to multiple causes at the same time:
- Geometrically determined thermal bridges form where the heat-supplying internal surface is smaller than the external surface. Typical geometric thermal bridges are building edges and wall corners up to the ceiling and floor.
- Construction-related thermal bridges result from changes in the cross-section of components. They occur, for example, on window transoms, mounting slots or window lintels, where the outer wall becomes thinner due to the component structure.
- If different materials come together in components and have different thermal conductivities, material-related thermal bridges are created. This is the case, for example, when combining masonry and metal in the form of steel supports in the external masonry. Thermal bridges caused by fastening anchors in composite thermal insulation systems (ETICS) are also material-related.
- Furthermore, convective thermal bridges are created due to leaks in the components. This may be the case, for example, of component joints or installation cable penetrations. Here the thermal energy is transported outwards by convection through air, gases or liquids.
CONSEQUENCES OF THERMAL BRIDGES
In many cases, cold spots on surfaces caused by thermal bridges are perceived by the inhabitants of the house as if there was a «draught» there. This results in an unpleasant indoor climate. Additionally, where the building envelope is colder, thermal energy escapes into the environment, increasing heating costs.
However, housing discomfort and additional energy costs caused by thermal bridges are only the most obvious problems. In cold areas, greater humidity accumulates due to the temperature difference compared to the surrounding surfaces. The warmer and therefore more humid ambient air condenses on the colder surface, creating ideal conditions for the development of microorganisms such as mold or bacteria. Thermal bridges are particularly at risk in the bathroom and kitchen, where the humidity is already higher due to use.
Over time, condensation can dampen the affected component and cause damage to the building structure. Furthermore, due to the temperature difference, stresses can build up in the components which can lead to cracks in the building envelope. This is one of the reasons why thermal bridges should not be underestimated or, if possible, should be avoided.
AVOID THERMAL BRIDGES
Once damp spots, mold or mildew stains appear, it’s too late. The best guarantee against thermal bridges in house construction is therefore – as with the construction partners of – professional planning and careful execution by the craftsmen involved in the construction. The common objective must be to build the house with as few thermal bridges as possible.
In addition to this, a compact structure with as few protrusions, corners and bay windows as possible helps to avoid thermal bridges. The more homogeneous the insulation of the outer shell, e.g. of the boxes and walls, fewer thermal bridges are created on the facade. Furthermore, components such as a balcony or roof terrace should be thermally separated using special insulating elements (Isokorb).
Defects caused by incorrect execution of joints and vapor barriers can be identified through the so-called «blower door test». is included in the flat rate price. This measurement is used to check the airtightness of the building and to identify leak points that need to be eliminated before the move.
THERMAL BRIDGES AND ENERGY CONSTRUCTION LAW (GEG)
The evaluation of thermal bridges is also a crucial part of the calculation of energy requirements according to GEG. The length-related heat transfer coefficient (psi value) serves as a concrete measure of the amount of heat that is lost through a component.
Firstly, the calculation of the thermal bridge according to GEG can be carried out without concrete testing with a flat-rate surcharge on the entire building envelope. Secondly, the flat rate surcharge can be halved if the details of the thermal bridge are carried out according to DIN 4108 Annex 2. Thirdly, existing thermal bridges can also be specifically taken into account through a detailed calculation of the heat losses of the components used.
High-efficiency housing standards without concrete evidence of thermal bridges can hardly be implemented in practice or require disproportionately high insulation thicknesses to be able to compensate for flat-rate supplements. In these cases it is therefore advisable to record the thermal bridges through a detailed calculation of the heat losses of the components used. For a financing request, construction partners provide your independent energy consultant with the relevant thermal bridge calculations for the control details they have installed. This allows your energy consultant to optimize the energy requirement calculation for your individually designed dream home. And this helps save on building envelope insulation costs and makes homes more efficient relatively cheap.
latest posts published
Elegance and versatility for your table
Plant shelf: transform your interior!
creative tips for your stay
Comfort and style at home
mix styles and dishes!
Transform your interiors with elegant pastel colors
Give a unique Boncoeurs gift
Olfactory elegance: reinvent your interiors
Brighten up your windowless space: effective tips
