How to predict moisture disorders? Which technical solutions to renovate the existing building? – HUMIBATex

The scientific approach lies on a state of the Art (hygro-thermo-aeraulic transfers and existing tools to study them), and the development of a tool feed by real datas mesured at a triple scale : the material, the experimental cell, and in real buildings before and after renovation. The materials required for the input data of the models have been characterized. The hygrothermal characterizations were carried out on samples taken directly from old houses and samples from the construction of the test cell. Simulations were carried out on 4 typologies of old walls with internal isolation (Brick, Concrete, Stone, wood/cob). The approach allows to propose a methodology and provide answers to key questions on which the architects and the owners will be able to rely to rehabilitate the existing buildings. The project allowed to understand the difficult question of the thermo-hygro-aeraulic coupling at different scales of the building. Different types of coupling have been explored: Co-simulation between two building codes (Wall – Building) and simulation in the same environment linking the simulation codes (Wall - Building). It turns out that the most operational solution for the multi-scale simulation of heat-air-moisture transfers in the building is linking. This solution introduces a bias into the prediction, but it tends towards security. The HUMIBATex tool have been developed starting from the partners' softwares to be able to meet the requirements of the technical solutions guide for building rehabilitation. Each simulation software was used to meet specific needs; The platforms have been able to work with different granularities and provide common or complementary responses to the indicators defined to predict energy consumption, occupant comfort and the risk of pathologies before and after renovation.

The HUMIBATex project is a fundamental research project coordinated by the CSTB. It also combines Cerema, Isover, Aldes, Ventilairsec and the laboratories LaSIE, LOCIE, CETHIL. The project began in January 2012 and lasted 48 months. Main results are: • Bibliographic Guide (http://www.batipedia.com/telechargements.html?id=800004) «Impact de l’humidité dans le bâtiment : diagnostics et retours d’expériences ». • In situ monitoring before and after retrofitting of 6 buildings. • Experimental cell construction and trials (with and without insulation). • Development of HAM co-simulation tools. • Technical Guide HUMIBATex. It includes i) the chosen methodology for calculating the pathology risk indicators in buildings, ii) the illustrated answers by the technical solutions resulting from simulation results to deal with the most problematic issues during rehabilitation of buildings. The HUMIBATex project complements the knowledge on coupled “heat-moisture-air” transfers in existing buildings by combining on site measurements in real buildings, laboratory tests and a large number of simulations.

Publication of technical guide

The partners have realized i) scientific production in different journals: Journal of Building Engineering, Journal of Building Performance Simulation, Energy Procedia…etc. They participated in conferences such as IBPSA International BS2013-Chambéry, Conference SIMURex Cargèse 2013, 13th day of studies of porous media 2016… 2 Phd thesis are associated at HUMIBATex: Julien Berger and Mohamed Yacine Ferroukhi

The rehabilitation of the existing buildings is a major stake to reduce of a factor the 4 gas emissions for purpose of greenhouse.
So that this effort is authorized by all it is necessary to propose complete technical solutions (insulation, ventilation) and acceptable for the professionals. These solutions must bring answers to the energy reductions but also to the comfort of the occupants and the durability of the solution suggested.
At the time of rehabilitations, the principal risk, badly apprehended at the present time as well in the practices as in the regulation, lies in a slow and irreversible degradation of certain components sensible to moisture (beams out of wooden, stones tender, old coatings, etc). This degradation can, in certain cases, to lead to the collapse of all or part of the building.
Moisture was indeed always the enemy number one of the building. Moulds, rot of wood, corrosion of metals are among the current effects of the dangerous connections that maintains water with materials and the works.
To bring viable solutions, our project falls under a step of energy restoration “total” of the park of existing buildings, by distinguishing the constructive times and modes (mainly “built old” on a side, “modern frame” of the other) and while seeking to couple the dependent aspects:
- with the thermal improvement of the envelope (current walls and connections),
- with the hydrous transfers through the envelope,
- ventilation and the permeability to the air,
- the consequences of the effects of moisture on the emissions of materials and the risks of moulds.
This study proposes to produce a guide of assistance to the rehabilitation of the existing buildings by proposing adapted solutions. This guide will be accessible by the professionals from the building.
To validate these solutions, a tool articulating the models and modules of simulations existing able to predict the power consumptions, the comfort of the occupants and the risks of pathologies related to moisture after restoration will be developed.
This tool will be validated by in situ measurements before and after restoration on real and occupied buildings and by measurements on an experimental cell to build.
The experimental cell will allow experiments in artificial climatic conditions, for better including/understanding the phenomena of transfers and in real climatic conditions.
The data input being essential to simulations, a list of the characteristics necessary to the models will be carried out on the basis of element existing and supplemented if necessary by measurements directly on the products.
The guide will be produced starting from the results of measurement of this study and will be supplemented by simulations of configurations suggested during the analysis of the existing built park. Thus the building owner or the project superintendent will have at his disposal a guide proposing of the checked and validated solutions of rehabilitation. If the guide is not sufficient, the tools developed in this study will make it possible to answer its request.