Browsing by Issue Date, starting with "2010-03-17"
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- The keep Cool II idea and strategy: from "cooling" to "sustainable summer comfort"Publication . Camelo, Susana; Goncalves, Helder; Laia, Carlos; Richard, M.The European Energy Performance of Buildings Directive (EPBD) explicitly refers to a "passive cooling techniques, primarily those that improve indoor climatic conditions and the microclimate around buildings". However, in Europe the demand for air conditioning is rising, especially in office buildings and is expected that the cooled floor area will be four times higher in 2020 when compared with 1990 figures. About 40% of our energy use is consumed in buildings and air conditioning represents a significant part. he overcome this problem conventional answer consists on to improve of the energy efficiency of cooling. However, this startegy showed limited results in terms of saving energy and reducing greenhouse gas emissions. In fact, cooling can be avoided (or the need to use energy for cooling) or significantly reduced without risking summer thermal comfort for building occupants, having thus the potential to achieve substantial reductions in energy demad and contributing to the overall objective of reduction CO2 emissions, minimizing the risk of the global warming and of the European climate protection commitments. This paper presents the conclusions of two surveys undertaken in the frame work of the Keep CoolII Project. One centered on evaluating current practices in cooling design, construction and operation, in order to obtain a feel of how widely good practices are known and use and as a basis for the subsequent study on incentives to remedy a set of key barriers and to reach the notion of summer comfort as a service. Indeed, efficient strategies for cooling have been studied for at least two decades, and several campaigns have already been implemented in the EU member states to disseminate knowledge on summer comfort efficiency since the 1990s. The other survey was undertaken in order to review the energy efficency criteria, in the national buildings codes, concerning summer comfort or mechanical cooling system in order to elaborate recommendations towards a sustainable summer comfort. This surver intended update, in a regional basis, the information regarding national building regulations, identifyin the measures adopted and delineating good practices concerning energy consumption, summer comfort and summer requirements. Finnaly, it should be stressed out the key role of the building designer towards sustainable summer comfort. Building codes requirements and design rules needs a proper use by the building designer.
- Solar XXI building : proof of concept or a concept to be proved?Publication . Panão, Marta Oliveira; Goncalves, HelderSolar XXI buildings is a prototype of low energy office building where passive and active solar strategies heve been applied to reduce the use of energy for heating, cooling and lighting, combining also an extensive photovoltaic façade for electricity production. Solar XXI was built in 2006 and is considered a high efficient building, close to a net zero energy building (NZEB), because the difference between the energy consumed and that produced is 1/10th of the energy consumed by a standard new office building. Its design includes a large number of energy efficiency concepts, such as a high insulated envelope, south sun exposure, windows shading, ground coling or stratification and cross ventilation. The windows solar gains and the effectiveness of shading devices were proved correlating soalr radiation, external and indoor air temperatures. It was also verified that ground cooled air has a temperature close that theoretical expected.
- Thermal performance of residential buildings with large glazing areas temperature climatePublication . Tavares, Márcia; Goncalves, Helder; Bastos, JorgeThis work presents the results of an experimental and numerical study of a residential buildings in a temperature climate, the paticularity of these bulding the large glazing areas around 65% to 85% of exterior façade. The thermal performance is presented and dicussed. The study was developed taking into account the implementation of monitoring during the summer and winter for a housing unit in an intermediate floor with only one façade in contact with the exterior (south façade) without solar protection by the glass (glazing area 80% exterior façade) located in Lisbon, Portugal (Latitude 40º N9; as well as detailed modeling of this unit using EnergyPlus for thermal simulation. The detailed model took into account the characteristics of the housing unit and the conditions under which it was monitored during the summer and winter. To simulate the detailed model under the monotored conditions the climatic data was cerefully introduced in the thermal simulation (climate file), the data was obtaines from the metereological stations of the National Laboratory for Energy and Geology (LNEG, Lisbon) for the same periods of the monitoring. From the detailed model different parametric variations were performed (summer and winter). Thus we obtained a set of effects that let you chek the parameters of major and minor influence on the thermal performance of housing units with large glazing areas situated in temperate climates. This work intends to provide tools and guidance to building designers with regard to the thermal performance of buildings.
- Portuguese thermal building legislation and stategies for the futurePublication . Goncalves, Helder; Panão, Marta Oliveira; Camelo, SusanaPortugal must evaluate, according to the Energu Performance Building Directive, the national requirements for energy performance of new buildings until 2011, which can be an opportunity to devise a national stretegy that tightens the minimum energy performance requirements. The present study intends to analyze the changes that should be introduced in the Portuguese Regulation to achieve highl energy efficient buildings. The objective consists on evaluating the relevant improvement of thermal envelope performance such as walls, roofs and floors thermal insulation (maximum U-values), air tightness (ventilation strategies) and windows (minimum shading requirements), heating and cooling systems, as well as wider use of integrated renewable energy. The study considers apartments with different shape factors located in different climatic zones. The optimizing methodology makes use of a genetic algorthm for the estimulation of primary heating and cooling energy indexes through a simplfied calculation methodology established by Portuguese Regulation.