François Garde

A multimodel approach to building thermal simulation for design and research purposes

The designers pre-occupation to reduce energy consumption and to achieve better thermal ambience levels, has favoured the setting up of numerous building thermal dynamic simulation programs. The progress in the modelling of phenomenas and its transfer into the professional field has resulted in various numerical approaches ranging from softwares dedicated to architects for design use to tools for laboratory use by the expert thermal researcher. This analysis shows that each approach tends to fulfil the specific needs of a certain kind of manipulator only, in the building conception process. Our objective is notably different as it is a tool which can be used from the very initial stage of a construction project, to the energy audit for the existing building. In each of these cases, the objective results, the precision advocated and the time delay of the results are different parameters which call for a multiple model approach of the building system

A detailed weather data generator for building simulations

Thermal buildings simulation softwares need meteorological files in thermal comfort, energetic evaluation studies. Few tools can make significant meteorological data available such as generated typical year, representative days, or artificial meteorological database. This paper deals about the presentation of a new software, RUNEOLE, used to provide weather data in buildings applications with a method adapted to all kind of climates. RUNEOLE associates three modules of description, modelling and generation of weather data. The statistical description of an existing meteorological database makes typical representative days available and leads to the creation of model libraries. The generation module allows the generation of non-existing sequences. This software tends to be usable for the searchers and designers, by means of interactivity, facilitated use and easy communication. The conceptual basis of this tool will be exposed and we will propose two examples of applications in building physics for tropical humid climates.

On the thermal behaviour of roof-mounted radiant barriers under tropical and humid climatic conditions: modelling and empirical validation

This paper deals with the empirical validation of a building thermal model, which includes a roof-mounted radiant barrier. We first present the thermal model, developed with a building simulation code prototype, the objective being to increase understanding of the thermal phenomena that govern the behaviour of the whole building. We then describe the experimental test cell, with emphasis on the details of the roof. A sensitivity analysis technique is applied to the model which shows that convective heat transfer is of great importance for the dry-air temperature of the roof air layer. The origin of the disagreement between measurements and model predictions is then identified as being due to one of the convective heat transfer coefficients. Once this is modified the agreement is found to be acceptable.

Study of moisture in buildings for hot humid climates

Humidity in buildings generates many disorders or disadvantages. A dry-bulb temperature of the air relatively low, strong moisture and wall surface temperatures very low characterize the interior conditions of the highland dwellings in Reunion Island, during the southern winter. This causes many disorders related to phenomena of condensation on walls: deterioration of the envelope, odor of mould. It is thus, significant to precisely know the evolution of the moisture in a building to avoid any disorder on the frame. In this study we will expose a series of experiments carried out on real residences in order to highlight main parameters of the problem. On the basis of these results, numerical simulations were used to extrapolate the behavior of this building on unusual climatic sequences, holding account various improvements of its constitution. A curative study and a preventive study were carried out on two different types of residences. The aim is to propose solutions to prevent deteriorations of the coatings due to the surface condensation.

Sky temperature modelisation and applications in building simulation

The sky temperature is an important parameter for simulation codes in building studies. A preliminary campaign of validation of a simulation software CODYRUN has demonstrated the misinterpretation of the radiative exchanges of long waves between the building and its environment. A bibliographical research has then led to the use models using dry air temperature to estimate sky temperature. However, these models has not been completely satisfactory as far as night clear sky are concerned. In this case, sky temperature remains overestimated. A research of a non linear model has been undertaken, leading to the use of neural networks with satisfactory results. Sky temperature is then calculated and reinjected into the simulation code. Comparison between simulated temperature and measures has turned to be acceptable.

Empirical validation of the thermal model of a passive solar cell test

Abstract The paper deals with an empirical validation of a building thermal model. We put the emphasis on sensitivity analysis and on research of inputs/residual correlation to improve our model. In this paper, we apply a sensitivity analysis technique in the frequency domain to point out the more important parameters of the model. Then, we compare measured and predicted data of indoor dry-air temperature. When the model is not accurate enough, recourse to time–frequency analysis is of great help to identify the inputs responsible for the major part of error. In our approach, two samples of experimental data are required. The first one is used to calibrate our model, the second one to really validate the optimized model.

Elaboration of global quality standards for natural and low energy cooling in French tropical island buildings

Electric load profiles of tropical islands in developed countries are characterised by morning, midday and evening peaks arising from all year round high power demand in the commercial and residential sectors, due mostly to air conditioning appliances and bad thermal conception of the building. The work presented in this paper has led to the conception of a global quality standards obtained through optimized bioclimatic urban planning and architectural design, the use of passive cooling architectural components, natural ventilation and energy efficient systems such as solar water heaters. We evaluated, with the aid of an airflow and thermal building simulation software (CODYRUN), the impact of each technical solution on thermal comfort within the building. These technical solutions have been implemented in 280 new pilot dwelling projects through the year 1996.

Post-occupancy evaluation and experimental feedback of a net zero-energy building in a tropical climate

Located in the French tropical Island of La Reunion in the Indian Ocean, the ENERPOS building was inaugurated in January 2009. The building is located in the Saint Pierre Campus of the University of Reunion Island. It was designed to be a net zero-energy building with mixed-mode air-conditioning systems in some areas (natural ventilation, ceiling fans, air conditioning) and efficient passive solutions sets usually used in tropical areas – i.e. efficient solar protection coupled with cross natural ventilation. This article reports the results of a recent user survey of the staff and students who use the building, and relates the users’ perceptions to some of the environmental control systems installed. Indications are that the users have been able to achieve thermally comfortable conditions for much of the year without recourse to the air-conditioning systems. However, there is still the need for more readily available information on how to get the best from the windows and the ceiling fan systems for the ever-changing groups of students, and staff who may only use the classrooms intermittently. For the more permanent staff group, preliminary indications are of improved health and productivity by comparison with their experience of other buildings.

A validation methodology aid for improving a thermal building model : case of diffuse radiation accounting in a tropical climate

As part of our efforts to complete the software CODYRUN validation, we chose as test building a block of flats constructed in Reunion Island, which has a humid tropical climate. The sensitivity analysis allowed us to study the effects of both diffuse and direct solar radiation on our model of this building. With regard to the choice and location of sensors, this stage of the study also led us to measure the solar radiation falling on the windows. The comparison of measured and predicted radiation clearly showed that our predictions over-estimated the incoming solar radiation, and we were able to trace the problem to the algorithm which calculates diffuse solar radiation. By calculating view factors between the windows and the associated shading devices, changes to the original program allowed us to improve the predictions, and so this article shows the importance of sensitivity analysis in this area of research.

Solution Sets for Net-Zero Energy Buildings: Feedback from 30 Buildings worldwide

Net Zero-Energy Buildings have been the object of numerous studies in recent years as various countries have set this performance level as a long-term goal of their energy policies. This book presents a unique study of 30 NZEBs that have been constructed and have had their performance measured for at least 12 months. The study is based upon an international collaborative research initiated by the International Energy Agency the Solar Heating and Cooling Programme (SHC). It is the first book to evaluate building strategies in houses, educational buildings and offices that have been demonstrated to work in practice. It examines how the design challenges of climate and building type have been addressed, and to what extent the various design approaches have been successful.