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

this reason it is essential to work not only on the envelope, but also on the behaviour of the building's users. The objective is to maintain a balance between the heritage value and maximising energy efficiency, with a focus on the overall balance of the building.

The relationship between thermal efficiency, ventilation and damp is a delicate one. It is necessary to be aware of the possible consequences that may arise if one of these aspects is affected in order to avoid destabilising the operation of the building. We are often called upon to deal with issues occurring on worksites after work has been carried out where we diagnose problems with damp connected with the installation of new windows (double glazing) with frames that are far more airtight than those that were previously fitted. The natural ventilation of the building is often found to be reduced and problems with condensation and mould have appeared (fig. 1 and 2). This is a classic example. The balance of the building is affected and unforeseen damage is caused. However, these problems could have been avoided with the use of a properly designed ventilation system. Another classic example concerns cellars. If one wants to make use of a cellar or make it less damp, the initial response is to increase the ventilation and heating. If the cellar in question suffers from dampness problems (perhaps less visibly so initially) and the dampness is able to migrate from the ground into the stonework, it will evaporate more quickly with the increase in heating and ventilation. The salts will then crystallise more rapidly leading to damage to materials, another unforeseen consequence. These two examples illustrate the importance of anticipating the possible consequences of any work.

With regard to maximising energy savings, we prefer to use the term “optimise” - it's sort of like saying: “Well, we're going to do what we can, but always in accordance with the heritage values to be conserved and the balance of the building, which must remain positive”. Where we want to satisfy the requirements of the EPB or any other regulation, we do everything possible to do so. However, in this programme, which is focused on heritage buildings, we want to approach things differently. We start with the building, determine the limits of any action and, through a series of minor or major interventions, aim to reduce energy consumption as much as possible without attempting to achieve an objective that is essentially theoretical. We adapt to the building itself. We don't want to reinvent the wheel. We will of course use innovative solutions where necessary, as there are materials that have not yet been extensively used or which are still on the expensive side but which can be employed when carrying out work on heritage buildings. In order to apply this

Fig . 1

Efflorescence from salts and damage to materials in a ventilated and heated cellar (© BBRI).

Fig . 2

Development of mould in a renovated vicarage, following the installation of new frames and double glazing without any system of ventilation (© BBRI).

102 | The scientific and technical centre for construction renovation laboratory: a contribution to heritage maintenance