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

ANALYSIS OF UNCERTAINTIES IN DYNAMIC THERMAL SIMULATIONS FOR OLD HOUSING: A CASE STUDY OF ONE APPARTMENT AND ONE HOUSE IN THE PARIS REGION

JULIEN BORDERON
CENTER FOR EXPERTISE AND ENGINEERING ON RISKS, URBAN AND COUNTRY PLANNING, ENVIRONMENT AND MOBILITY (CEREMA) - REGIONAL LABORATORY OF STRASBOURG (FRANCE)

THE EXISTING TOOLS FOR EVALUATING BUILDINGS AND THE UNCERTAINTIES ASSOCIATED WITH THE INPUTS FOR DYNAMIC THERMAL SIMULATIONS ARE PRESENTED, ALONG WITH A WAY OF EXAMINING THE LIMITATIONS OF MODELS WHEN APPLIED TO EXISTING BUILDINGS.

This presentation centres on the method that we have applied to a certain number of buildings and that we continue to use. In fact, our approach has been deemed sufficiently beneficial by the French Ministry of Ecology, Sustainable Development and Energy that we have been asked to go even further. I will illustrate my talk with studies carried out on an apartment located in a building in the 16th arrondissement of Paris and a house in the inner suburbs of Paris (figs. 1 and 2).

THERMAL SIMULATION APPLIED TO OLD BUILDINGS

Dynamic thermal simulation is one of the common auditing tools for buildings and therefore also for old housing. In fact, to perform a general audit, a number of aspects are worked on: the health of the building; its functional state; its suitability for purpose; the comfort of occupants; its strengths and weaknesses; its heritage status and elements that need to be preserved are evaluated. The energy status of the building is also addressed through consumption, thermal efficiency, performance of systems and management and use. It is then possible to use simulation tools, if there is sufficient concern, to compare or test different packages of solutions. An attempt is made, via this energy audit, to determine typical consumption and how it is broken down by type of use in order to obtain itemised distribution graphs of heat loss. The ultimate objective is to establish priorities. This also enables the building's behaviour when used in another way and/or independently from the occupant's habits to be simulated. To explain this further: the energy bills of a person heating an apartment to 26°C are higher than those of a person heating the same place to 20°C. Thermal simulation of a building allows the consumption specific to an apartment in a classic usage scenario to be determined. In France, we refer to the conventional usage scenarios of the thermal regulations. A reference condition can therefore be obtained prior to works being carried out and used to model different simulations of packages of work. In order for our simulations to be reliable and be able to forecast the investment payback period, precise and realistic data are required. If our target is, for example, 80 kWh/m²/year and our initial situation indicates 200 kWh/m²/year, even though in reality our building is at 150, the general saving produced by the works will be a lot less than expected. It will therefore be harder to pay off the investment and could even result in a situation whereby it is not economically viable. Simulation also facilitates

56 | Analysis of uncertainties in dynamic thermal simulations for old housing