To put it simply, the parts of buildings with increased heat transmission are called thermal bridges. The reason of their formation can be the geometrical shape, structural nodes, application of materials with different thermal insulation capability in uneven thickness etc.
The most frequent thermal bridges are socles, ring beams, lintels, radiator enclosures, parapets, reinforced concrete pillars, cantilevered balcony slabs, window and door connections, wall corners and wall connections.
The absence of proper prevention of thermal bridges can cause significant heat loss. The moistness generated by surface condensation has a contrary effect to the comfort of the room. The low temperature of inner surfaces and high relative humidity often provide a good breeding ground for mould-growth, surface damages and aesthetic problems. Preventing the development of thermal bridges should be taken care of in the design phase.
Thermal insulation by STYROFOAM™ XPS may result in significant advantages:
• reduction of heat loss – energy saving (the transmission heat loss can be reduced by cca. 10%),
• avoidance of mould-growth,
• prevention of structural problems — surface condensation, cracks, aesthetic problems,
• improvement of comfort.
STYROFOAM™ XPS insulation boards are
• not sensitive to moisture,
• resistant to mechanical impacts, and
• they retain their insulation capability and strength during and after the construction period.
Due to the high resistance to water-vapour permeation, no vapour barrier is normally required when the insulation is situated on the internal side. To avoid thermal bridges, the accurate design of the structural details has decisive importance. The insulation value at thermal bridges and socle is recommended to be at least equal to the performance of the adjoining walls, roof or floor slab.
Thermal bridges require special attention because, arising from the intensive thermal insulation of the surface, heat flux density and vapour migration are even more intensive at the critical structural nodes.
STYROFOAM™ XPS boards can be favourably used as the thermal insulation of reinforced concrete structures: ring beams, lintels, pillars, columns as their permanent insulated formwork, as well as in window frames, parapet walls and building socles. The thermal insulation of the edges of flat roofs, parapet walls, are often not or only insufficiently resolved, which may considerably decrease the efficiency of the thermal insulation of the roof surface depending on the geometrical proportions.
INSTALLATION OF STYROFOAM™ XPS
The STYROFOAM™ XPS extruded polystyrene foam thermal insulation may be installed as early as before concreting as permanent insulated formwork or subsequently by gluing. In both cases, it is recommended to use additional mechanical fastening.
Arising from the relatively high resistance of XPS boards to vapour-diffusion, vapour condensation created in the connection plane of the thermal insulation and the wall usually does not reach the critical level. In the case of normal internal air conditions (20°C, 50-60% rel. humidity), condensation in the structure, in general, reaches only an extent that dries up in the summer period.
If the existing wall is made of bricks with relatively good thermal insulation value, there will be usually no vapour condensation. However, in buildings with high air moisture content (swimming pools, laundries, kitchen plants), a vapour barrier will have to be installed on the internal, warm side of the thermal insulation, and its efficiency checked by calculation.