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ONLINE BRUSSELS HERITAGE - ONE-DAY SEMINAR - 11/12/2014
The same process can be seen after the 1950s: improvements in heating systems resulted in a greater number of openings in façades, in a search for ever more Light. In Neoclassical buildings, the proportion of openings to solid wall is 1/3 to 2/3. In the first quarter of the 20th century, it reached 50/50. With technical advances, everything then became possible: strip windows, glass walls, etc. An examination of the evolution of construction techniques and their impact on energy consumption shows a widespread falling off in the postwar period (fig. 9).
There are numerous difficulties involved when renovating an old building, depending on the construction techniques used. Modifying spaces is a complex operation that can produce problems, most notably an increase in thermal bridges. This risk arises when working on reinforced concrete, beams, windowsills, lintels, etc. Partial insulation of an area can be dangerous; problems can arise in places where the thermal conductivity is greater. The less standard the façade -for example, when there is a double wall-the more serious are the thermal bridge-related issues. Specific solutions to address the problems inherent in these types of buildings will have to be used for renovations. In this regard, backyard annexes constitute a specific problem. These outgrowths, made from lightweight materials, pose real problems in relation to density. Erected with no consistency between them, these small structures generate thermal bridges in all directions. They are generally less dense than the main building. Carrying out work on annexes has a high potential for energy savings.
Fig. 8
The thermal conductivity of opaque walls is a reflection of the construction techniques used. These techniques are based on a constant: a solid load-bearing wall, which explains the relative uniformity of the results and why they fall so considerably short of the performance target formulated by the EPB (fixed at 0.4) (© Apur).
Fig. 9
Over time, the thermal properties of the buildings deteriorate (© Apur).
30 | Urban forms, typology and improving the energy efficiency of old Brussels buildings
