A reverse engineering method for evaluating the thermal behavior of a historical building

Today, many developed countries are trying to reduce the overall energy consumption of buildings, as well as their greenhouse gas emissions. To meet these targets, many buildings need to be renovated. Many methods are used around the world to ensure the success of building renovation projects. These include

• energy audit ;

• building performance assessment ;

• quantifying energy savings ;

• economic analysis;

• risk assessment and measurement & verification (M&V) of energy saved.

An energy audit is essential for energy-saving renovations. Energy audits vary in scope and depth. According to the ASHRAE manual, the energy audit can be classified according to three levels:

• level 1: overview of evaluations ;

• level 2: energy study with analysis ;

• level 3: detailed energy analysis.

Numerical models are an important part of detailed energy analysis. They can also be used to predict the energy saved after a series of renovation projects.

By knowing the characteristics of a building, we can easily calculate its STD and obtain its thermal behavior. This applies to buildings for which the technical database is available. If the technical database is missing, there are two reliable ways of obtaining the wall's thermal resistance:

• the first is a destructive method, i.e. making holes in the walls (coring or endoscopic method) to understand their composition and calculate their thermal resistance;

• the second is a non-destructive method using a fluxmeter to obtain the thermal resistance of the wall and compare it with the destructive method. Ficco et al. have demonstrated the accuracy and reliability of the second method for historic buildings.

In this work, an attempt was made to involve the said non-destructive method in an inverse methodology, in order to obtain the thermal behavior of the building, without using any destructive operation.

The work is carried out at ICAM Lille, which was built in 1898. The establishment is therefore considered a historic building in which destructive operations are not recommended. On the other hand, there is no information about the composition of the walls. The ICAM buildings therefore present a good opportunity to apply our methodology and testing.