The passive cooling techniques such as night time cross ventilation is potentially an interesting strategy to provide substantial cooling energy savings in warm climates. The efficiency of the night cooling ventilation is determined by three main factors: the external air flow rate in the room, the flow pattern and the thermal mass distribution. Most of the software used to simulate building thermal performance assumes natural convection in the enclosure; therefore the convective heat transfer coefficients for internal room surfaces are underestimated.
The potential for passive cooling of roof slabs incorporating an air cavity is important with respect tothermal comfort. Roof systems in traditional buildings, incorporated a ventilated roof or an air cavity.The concept has been proposed again in contemporary buildings in the construction of roof slabs,using a modular formwork system, where the cast in situ concrete slab is isolated from the screed with the introduction of a ventilated air space. The cavity is primarily intended to curtail the conduction and inward radiation of heat from the intense solar insolation on the concrete roof.
Natural ventilation driven by the combined forces of wind and buoyancy has been studiedexperimentally for a building flanked by others forming urban canyons. The steady ventilationestablished in an isolated building was observed to change dramatically, both in terms of the thermalstratification and airflow rate, when placed in the confines of an urban canyon environment. Theresulting ventilation flows and internal stratifications are presented for different combinations of windspeed, opening area and location, and canyon width (building density).
The process of implementation of the EPBD in Austria is now carried out for several years. Thecalculation scheme for asset rating is finished, the operational rating procedure is still being discussed.One of the major problems in Austria is the fact that most building laws are under the responsibility ofthe nine Austrian provinces. Therefore all political decisions like baseline and limits of the energydemand for the building codes are difficult to achieve. These values are therefore still underdiscussion.
The EPBD prescribes an energy performance certificate for buildings. According to the nationalimplementations of the EPBD for non-domestic buildings the specific data of the building will begathered during the certification process and combined into a multi zone model describing buildingand building systems from an energetic point of view.
Cross ventilation is one of the most important techniques for maintaining a comfortable indoorenvironment in hot and mild seasons with less cooling energy. But, at present, it is difficult to designindoor environment under cross ventilation because there is insufficient knowledge to evaluate theeffect of cross ventilation quantitatively. Thus the full-scale model experiment has been done in a large wind tunnel to examine the airflow property in the cross-ventilated space.
In the first phase of the current project, the ventilation rates of occupied houses in the northern region of Japan were investigated from 2001 to 2005. It was revealed that, despite installing mechanical ventilation system, low ventilation rate was found in many houses. The causes were believed attributing to lack of cleaning of grills, filters and insect protection meshes. The second phase of the project was to investigate the causes and resolve the problems. This project was started in 2005 and 12 houses installed with mechanical ventilation system were investigated.
Important oversizing factors are observed for room air-conditioners leading to important energy wastes and costly summer peak demands for utilities. This article intends to show that sizing decisions should be based on dynamic simulation results and include an assessment of the air conditioner part-load performance. The sizing methodology established is applied to evaluate different oversizing levels for different types of buildings, climates and systems. This enables to compare our methodology to typical rules of the thumbs applied in France.
In this article the concept of a new energy-efficient office building and results of a 3-year monitoringare described. The monitoring was performed within the German funding programme ENOB.In this building most of the offices are naturally ventilated and passively cooled. Another focus of theenergy concept is on regenerative heating.Monitoring results show that the integrated planning enabled a very low consumption of energy forheating, ventilation, cooling and lighting.
This work lies within the concept of positive energy buildings. The aim is to develop an activemanagement of local free energy (solar, air and earth) inside the envelops by convection heat transfer and by the use of phase change materials (PCMs) in order to store or release heat when needed. A 1D RC network simulation tool has been developed for different standard fronts including a solar air collector and a double skin faade (south frontage), leading to the thermal simulation of a room with different configurations, with or without PCMs integration and for ventilated envelops.
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