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

sequences from this development: some of them are of historical importance and external insulation must be prohibited. However, certain types are suitable, as they have changed a great deal. It would be necessary to study the details of these changes; to see how people have adapted the spaces, which is acceptable with such changes; as well as how they should be managed, etc. Insulating renders could offer a solution. Nevertheless, there is no universal technical solution applicable everywhere at all times. Certain zones such as the “experimental project” in La Roue, a former technology showcase, could be returned to its original vocation through the use of innovative renovation solutions. Clearly, such an approach requires moving away from the regulatory mindset.

INTERIOR INSULATION: A SOLUTION THAT CAN CREATE PROBLEMS

Interior insulation does not require planning permission. The absence of any requirement for permission gives the impression that the technique belongs to the realm of basic DIY. In reality, it is the most complex types of insulation as it can create a lot of problems, especially in old buildings. This doesn't mean that it shouldn't be used, only that great care should be taken when it is.

We have gained substantial experience in Paris with the use of brick, both in terms of insulating it and learning about its inherent problems. We have noticed the harmful effects of interior insulation on numerous timber frames. When the structure is affected and the building becomes unhealthy, the only solution is demolition/reconstruction. The advantage and disadvantage of using brick is that it retains dampness well. It may take five or ten years, or even longer, for problems to appear. Interior insulation often prevents the dampness stored by the bricks from drying out. This is what we often encounter in west/south-west facing walls, pounded by rain, or in walls covered with glazed bricks, which are highly permeable to damp.

If we want to achieve the standard of U= 0.4 or 0.2, highly insulating materials such as polystyrene or rockwool will have to be used. However, solutions such as these can be counter-productive over the long term. By conceding that no attempt will be made to achieve the standard, we open up the possibility of using materials that are compatible with old structures (such as hemp concrete, cellular concrete, lime renders, cork, etc.] whose thermal properties are, today, almost on a par with polystyrene.

We have tried, on certain projects, to aim for a performance of 0.8 and not 0.4. Meter readings indicate a building now using 80 kWh. The cold wall effect has been eliminated and the residents no longer suffer from a lack of comfort. They are therefore using less heating. Once again, it involves considering the actual situation and actual behaviour of the residents. Nowadays, there are other materials besides polystyrene which, admittedly, are less efficient in theory, but with which interesting things are being done in practice.

CONCLUSION

To conclude, I want to return to some key points from the study. Firstly, it would be interesting to territorialise energy dependence so as to be able to prioritise energy ambitions at a regional scale. It is not possible to be efficient everywhere; choices must therefore be made, especially since budgets are, in general, limited.

Another area worthy of investment is planning regulations, which have a role to play in guiding the phenomenon of densification. This involves, among other things, the preservation of certain interior green spaces to prevent the emergence of urban heat islands.

As regards buildings in the strict sense, improving knowledge about the existing stock and their specific features requires the collection of a large amount of statistical data on energy consumption. This initial step will also help to refocus the level of public subsidies for the performance required in old buildings and validate the effectiveness of work by means of “before and after” comparisons.

Finally, the question of capitalising on feedback arises: knowing what has been done, what works, what doesn't work, etc. over the long term is essential in order to assess the actions taken and decisions made. The dogma that states “a good building is one that is airtight and thermally insulated” is not a valid one. Greater subtlety is required. There must be room for observation and experimentation. Help must be provided to improve the qualifications of project managers and promote the smart approach to buildings and renovations.

Translated from French.

33