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

The various examples cited above also illustrate how an intervention to one element often means that a much larger intervention subsequently becomes necessary: insulating the roof quickly becomes replacing the entire roof; insulating windows becomes replacing windows; insulting the façade becomes replacing the façade. In principle, rebuilding monuments with respect for the original appearance but resulting in a high energy performance version is not part of the heritage conservationist's task. Reconstructing the image, and nothing more - and many interventions intended to improve energy performance have this result - goes hand in hand with the loss of genuineness, authenticity. It's a new façadism.

Such restorations are no longer a sustainable intervention either, and not in the spirit of the task of heritage preservation: that is, to preserve, repair and reuse as much as possible, taking the value of the elements and the maximum possible life span of the materials into account.

The extent to which interventions require radically altering the contours of existing buildings makes it an expensive undertaking. The costs are not always in balance with the benefits. Indeed, quite the contrary can be true: making buildings energy efficient while preserving the heritage appearance comes with a very high price tag. This can mean interventions which are out of proportion on several levels.

However, improving the energy performance of buildings also plays a role in sustainability. If we take a step back and shift our focus from the performance requirements for each individual building component to take a more global view, envisioning a long-term future; if not every element must meet maximum performance criteria; if we also consider the way in which energy is generated and how people use and maintain their buildings; then the same questions can be asked on both of the opposing sides - heritage and energy -and common answers formulated.

The improvement of the energy performance of existing buildings also raises questions regarding the life span of the materials; whether replacement is necessary; and whether replacement is dealt with in a responsible manner, such as taking into account the energy needed for waste disposal and production of new materials, or whether we can reuse materials. In this common field, it must be possible to examine the elements’ specific values (material, cultural, financial, historical, etc.). it must also be possible to examine the intrinsic qualities of the existing buildings and to evaluate whether or not we can operate them or use them in a more energy-efficient way. Consider, for example, inertia, density, ventilation options, etc.

It must be possible to search for a healthy balance between the extent of the operations and the potential benefits (financial, energy-related, material, etc.). Is there a good return on investment time? It must be possible to evaluate the real impact of the interventions by measuring the results in order to adjust calculations and models. Finally, it must also be possible to carry out a thorough analysis of the possible risks and the side-effects (condensation, frost, moisture, etc.).

This way of thinking will lead to a global approach and higher global-efficient performance; an upgrade at building, block and city level; and to high energy performance historical cities.

Translated from Dutch.

Fig. 16

Preschool, indoor play area after being restored to its original condition, Sint-Gisleinsstraat, arch. V. Horta, 1895 (Ch. Bastin & J. Evrard, 2000 © KCML).



22 | Architectural heritage and energy performance