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

calculated based on the actual, measured consumption of the houses;

b) with an ROI of less than 20 years, calculated based on the theoretical, calculated consumption of the houses.

The measures considered feasible are those with the shortest return on investment time, namely:

1. insulating the roof and roof windows;

2. making the shell airtight;

3. installing more efficient lighting;

4. installing more efficient heating; The total costs for these measures can be estimated at EUR 75 to 150/m2 of heated floor space.

A 75% reduction in energy consumption is feasible by apply ing all of the measures provided in the management plan.

The total costs for these measures can be estimated at EUR 400 to 700/m2 of heated floor space. This includes the measures with a ROI of 100 to 150 years, such as insulating the façades. This very long ROI is, in combination with the large impact on the heritage, the reason why such works are subject to a mandatory audit before the Brussels-Capital Region can grant subsidies for them.

For clarification and rectification purposes, it must be noted that:

• these calculations are valid assuming a steady energy price; in the case of increasing prices, the return on investment time will decrease;

• these calculations do not take future maintenance costs into consideration, costs which are certain to arise as the return on investment times are quite long. The maintenance costs will increase the return on invest ment times.

CONCLUSION

The Heritage Management Plan for the Le Logis and Floréal garden cities became operational in 2014 in the legal framework for urban development which recently came into effect in the Brussels-Capital Region. The instrument was realised over a period of 15 years and in several phases and versions; the energy section is fully integrated in the most recent version. Thanks to an in-depth study of the original condition of the houses, the composition principles and the strengths and weaknesses of the 1,060 residences, heritage-friendly measures were provided to save energy and to keep energy bills as low as possible for the residents. The position taken here is to prioritise measures which will result in a maximum reduction to energy bills with a minimum investment. Thanks to a preliminary, calculated evaluation (audit) the conclusion can be made that it is possible to reduce the energy bill of a residence by 50% with affordable, energy-saving and heritage-friendly measures with am ROI of less than 20 or 50 years, depending on whether the calculations are based on the calculated consumption or the actual consumption.

This big difference shows, once again, that:

• considerable, affordable energy savings are possible and are also feasible for large scale imple mentation;

• a deeper knowledge of the hygro- thermal behaviour of historical heritage is needed in order to explain why current calculation methods for energy consumption deviate considerably from reality, and to understand that standard solutions for energy saving applied to newbuilds do not deliver the expected results or can even cause problems.

The complete Le Logis and Floréal management plan can be found on the website of the Direction des Monuments et des Sites:

http://bit.ly/1iMnupW

Translated from Dutch.

NOTE

1. In 2007, two houses from Fforeaiwere added to the listing when it became apparent that they too were built before 1940.

2. Houses were sold to private owners from the outset.

3. For a possible energy upgrade of all the Le Logis and Floréal houses.

4. The audit takes into account the specific qualities of each house in its current condition in relation to renovations, energy measures, technical installations, etc.

5. The actual consumption figures for the two houses were incomplete, but based on the figures available it is safe to assume that they consumed more than 2.5 times less energy than calculated.



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