ONLINE BRUSSELS HERITAGE - ONE-DAY SEMINAR - 11/12/2014

lost. However, there is significant potential for energy improvements in the rear façade, particularly when it comes to the annexes, as we saw in the presentation by Julien Bigorgne from Apur (see p. 24-34). Added to these qualities is the comfort of these old houses in summer, most notably because of the difference between the temperature in the back yard and that in the street, creating a cooling stack effect. The flexibility of the design is also an asset, as discussed in previous contributions. This design, which operates based on the “box” principle, enables each room to be turned into more or less airtight compartments in the building, heated in different ways depending on the season. The entrance hall, often sealed by an internal door positioned at the top of the stairs leading to the raised ground floor, also serves as a buffer space in terms of heat. There are other mechanisms that also enable the occupant to control comfort, such as interior or exterior shutters. While Venetian blinds have today largely disappeared, they were highly popular at the end of the 19th and beginning of the 20th centuries. Old postcards show that most of the buildings on the city centre boulevards were fitted with such blinds. Venetian blinds filtered daylight, from which people protected themselves to a greater extent than today, and also helped to combat summer overheating. The majority of Brussels houses at the time had rainwater cisterns which could be used to supply wash boilers, toilets, etc., by means of a pump.

Another advantage of these old buildings was the extremely long lifespan of the components from which they were made, including second fix components such as exterior joinery. The tendency today is to systematically replace old window frames in the name of saving energy, even though they are often in reasonably good condition after a hundred years or more of use. Yet the design of this old exterior joinery enables localised repairs to be carried out, for instance replacing the window sash bottom rail or a supporting member (lower window sill). The blue stone slabs on the balconies can also be repaired. Traces of work are sometimes visible: insertion of stone plugs to fill a gap; metal staples which are reminiscent of stitches to strengthen a crack; etc. In an old building, almost everything can, in theory, be repaired. What defines the know-how of the craftsperson

Fig. 6

An owner with a love for heritage renovates his house. He removes, among other things, a suspended ceiling installed in the entrance hall in the 1970s-1980s. At the time, it was seen as essential to lower the height of ceilings in order to “heat less air”. However, heating air requires little energy compared to heating materials. Suspended ceilings like these which, moreover, are not airtight, are useless from an energy perspective (© P. Brusten).

Fig. 7

The observation that the single-glazed aluminium window frames of the same era were not energy efficient is identical. It was then considered essential to ensure air tightness. However, today, it turns out that these frames are significantly worse from a heat transmission point of view than the single-glazed wooden frames that they replaced. Now, these aluminium window frames are, in turn, also being replaced (photo by author).

108 | Sustainable renovation of a Brussels house: a challenge for building tradesmen