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

innovations which offered a certain level of comfort against the cold (e.g. locks and lay-out of the rooms), overheating (e.g. shutters, thermal inertia), etc. However, due to a rise in energy costs there is a risk of the residences being heated, used and modified incorrectly. The problems which may arise can be detrimental to both the conservation of the heritage and the health and comfort of the residents.

Cenergie's energy study and audit was performed in compliance with the management plan in order to be eligible for regional subsidies. The starting point of this approach was the improvements regarding energy and interior climate provided for in the management plan. It then examined the energy performance of each specific case⁴; based on this, the most efficient measures are suggested. Jonathan Fronhoffs from Cenergie tells us more about this study in his contribution (pp. 48-53).

Limitation of energy needs with an emphasis on improving comfort

In the Trias Energetica, it is assumed that a sustainable building first limits its energy needs and, secondly, makes use of renewable energy sources instead of wasting fossil fuels. The first measure is usually realised by insulating the outer shell. Not all types of insulation used on the outer shell are equally efficient; the management plan requests that this efficiency -with regard to finances and energy- be taken into account in order for a project to be granted a subsidy.

However, limiting energy needs can also be achieved in ways other than insulating the outer shell, namely by creating a feeling of comfort for the residents at a lower room temperature. It is, after all, widely known that feeling comfortable is influenced not only by the temperature in the room but also by drafts, humidity and air quality. This is called the interior climate. By avoiding drafts, humidity and cold surfaces, a feeling of comfort can be created at a lower room temperature. In this way, less energy is lost through the outer shell through conduction, convection and air leaks. In the audit style developed by Cenergie it is assumed that the average (day and night) room temperature can drop by 1°C after comfort has been restored. This alone produces a considerable saving, without loss of comfort. We are all familiar with the examples of convection heaters and the cosy heat they emit when it is cold, or the pleasant feeling of a cold, sunny day.

Measures which benefit comfort and health are also beneficial to energy savings, but saving energy is not necessarily beneficial to comfort and health. Insulating the outer shell produces generally acceptable, calculable energy savings. Solving comfort deficiencies influences the energy bill indirectly; the energy loss decreases because the difference between the inside and outside temperature is decreased. Air temperature is a decisive factor in the influence of the thermal resistance of the outer shell on the energy bill. If the room air temperature can be lowered, the efficiency of insulating the outer shell decreases.

Insulating the outer shell and interior climate comfort are very closely connected, but nonetheless clearly distinguishable. They influence one another, but require different actions. The former mesures are often less heritage-friendly than the latter; therefore the management plan characterises the measures according to this distinction.

In short, the management plan provides the following measures to limit the energy need, in descending order of priority, by:

• improving comfort (interior micro climates, humidity, etc.);

• improving the airtightness of the shell;

• insulating the shell (roofs, floors above non-heated spaces, façades);

• improving the performance of equipment (lighting, heating, sanitary fittings, hot water).

These measures have been refined into a dozen specific measures, listed in the figures 5a and 5b:

• from 1.1 to 1.5: comfort and hygiene

• from 2.1 to 2.6: insulating the shell

• 5: energy-efficiency of the tech niques

This appendix also summarises all the works from the technical provisions (T02) which contribute to one or more of the aforementioned measures, and demonstrates the connections between them.

Lastly, figure 6 shows the location of the various measures using the façades and design plans of one type of house (LLw_D).

The energy results of the heritage-conformance measures

Both as an example and for research purposes, two specific houses were examined in the energy audit to ascertain the exact energy performance of specific measures (see pp. 48-53). Clearly, two houses is a very small sample to draw conclusions from, but for the time being this small study gives us an

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