THE ENERGY FUTURE OF EXISTING BUILDINGS IN BRUSSELS: BETWEEN PRESERVATION AND PERFORMANCE

to the greater density. The differences can be as much as 10%.

An analysis of green spaces reveals microclimate disparities, another form of territorial inequality. Each neighbourhood has a unique climate. The enclosed blocks from the late 19th century, for example, are urban creations where nighttime ventilation occurs naturally during the summer. Figure 3 shows a housing block the layout of which produces a significant thermal contrast between the green interior and the surfaced public space. This has the advantage of creating a stack effect, which is an excellent alternative to air conditioning. The natural ventilation inherent in the building is assisted by the presence of landings and the resulting offsetting of levels (fig. 4). The cellars also play a role in this phenomenon, as do the chimney flues. These are often blocked off during renovations to install controlled mechanical ventilation (CMV), which results in a loss of the vertical stack effect from the chimney and its air vents. This can eventually make things unpleasant as if the building is insulated, airtight and a CMV system replaces the chimney, this can create the ideal conditions for problems to arise during the summer months.

The design of the various types of single-family dwellings is flexible. It can be seen that pressure on land caused these spaces to gradually shift and single-family houses to transform into standard apartments. The adaptability of the design is interesting because, in reality, it enables each resident's energy consumption to be reduced. Indeed, if it is possible to move from a single-family house, housing three or four people, to three apartments; if there is a financial advantage to this division and, moreover, energy savings are achieved, then the entire inner ring becomes a focal point; this therefore results in a high demand for housing. These are natural phenomena and occur as a result of a favourable market. The increased density is based on a relatively simple adaption of the design. The stairwell, for example, can easily incorporate the communal areas as this space was, from the outset, conceived in this way. However, this transformation also produces problems: three apartments potentially presenting damp rooms on all floors. Yet, when renovating, dampness is a basic fact. Any audit starts with the bathrooms as hydrometry plays a central role.

MODIFICATION OF SEQUENCES

Our work has led us to address architectural heritage at an urban scale, focusing on high-density developments, the quality of spaces, etc. We are working on the principle that, where renovation implies the partial or total revision of building complexes, an urban analysis provides elements

Fig . 3

Top view of natural stack effect at block scale. The difference between how the ground is treated in the central courtyard (entirely covered in plants) and the public space (fully surfaced) is likely to create a pronounced thermal contrast which initiates effective natural ventilation (between the street and the yard). The green areas have the capacity to retain water, which evaporates during heat waves (Produced with Brussels Urbis © CIRB).

Fig . 4

Cross-sectional view of natural stack effect at the building scale depicted between the yard and street. The landing adds a vertical component to the stack effect (© Municipality of Ixelles).

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