Towards a strategy to zero energy buildings (ZEB) concept

The energy consumption in buildings and the need for its reduction has been since the late 60’s and 70ś a main question among professionals (designer, architects, and engineers), legislators and users around the word. Reduction in energy demand for heating for instance was implemented in the so called Solar Buildings (with reduction of 70 to 80% in the heating demand). The building regulation start putting targets, in the overall annual energy consumption xx kWh/m2 year, and some achieve the level of standards, imposing very low values, such as Passivhaus standard which fundamentally consists of an energy limit (net useful energy demand for heating of 15 kWh/m²/year and a total primary energy consumption of 120 kWh/m²/year). Now we are dealing for a new concept, in which those values approach zero (ZEB) or even minus, which correspond to building which produce more than what they spend (ENERGY PLUS BUILDINGS). This paper discusses some of the main issues regarding the strategy to achieve some of these goals in the future

Recommendation on Summer energy efficiency on national building codes

The building regulations have a major role in controlling and limiting the energy consumption of the building sector. The Thermal Building Regulations of the European countries although had followed the EPBD Directive in what concerns the methodologies, differs on the re-quirements and recommendations on summer comfort and energy consumption for cooling, due to the particular conditions of each country. A review of the national building codes concerning envelope constructive solutions (opaque and transparent), thermal mass, ventilation rates, energy consumption methodology and correspondent values limits has been undertaken for the participating countries of the Keep-Cool II Project and, was extended to other countries, by consulting building codes, technical reports concerning energy use in buildings and by direct contacts with colleagues. The goal of this analysis consists on put in evidence the different strategies adopted and try to share and to supply information and experiences in so far as, the energy demand for cooling in European buildings is the energy use in the building sector with high increase rate among the other energy uses. In fact, cooling can be avoided or significantly reduced, with-out risking summer thermal comfort, by means of mature passive cooling solutions, renew-able energy sources and reducing internal heat gains. This present report summarizes, in Chapter 1, the information that has been compiled from questionnaire answers of partners of the Keep Cool II Project: Austria, France, Italy, German, Portugal, Slovenia, Sweden and United Kingdom. Chapter 2 summarizes de final remarks and conclusions of the building regulations related to summer comfort and energy for cooling in or order to contribute for the dissemination activi-ties. In the Annexes are the questionnaire (Annex A) and the systematized replies to the ques-tionnaire in a comparative form (Annex B), In the Annex C is the name of the experts that have answered to the questionnaire by country and institution. A review of the national build-ing codes for other European countries is presented In the Annex D: Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Greece, Hungary, Ireland, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Romania, Slovakia Republic, Spain

Solar XXI building: Proof of concept or a concept to be proved?

Solar XXI building is a low energy office building where passive and active solar strategies have been applied to reduce the use of energy for heating,cooling and lighting, combining also an extensive photovoltaic façade for electricity production. Solar XXI opened in 2006 and is considered a high efficient building, close to a net zero energy building (NZEB), where the difference between the energy consumed and that produced is 1/10th of the energy consumed by a Portuguese standard new office building. Its design includes many energy efficiency concepts, such as a high insulated envelope,south sun exposure, windows external shading, photovoltaic panels heat recovery,ground-cooling system, daylighting, stack effect and cross ventilation. The solar gains of the windows and the effectiveness of shading devices were evaluated in order to correlate solar radiation, external and indoor air temperatures.It was also verified that amplitude-dampening of ground cooled air ranged between 5 and 8 C, following the trend of the analytical solution for heat diffusion of a cylindrical air/soil heat-exchanger

From solar building design to Net Zero Energy Buildings: performance insights of an office building

Net Zero-Energy Buildings Performance has gained more attention since the publication in 2010 of the EPBD recast [1]. Successful implementation of such an ambitious target depends on a great variety of factors. With a literature full of theoretical advice and a building industry rife with myths about the value of technologies, the present study intend to unveil an sustainable framework for sharing insights into NetZEB methodology applied in an Portuguese office building, Solar XXI, based on the authors experience in the ongoing research carried out within International Energy Agency SHC Task 40 - ECBCS Annex 52, "Towards Net Zero Energy Solar Buildings”

Energy performance certificate: a valuable tool for building-to-grid interaction?

New challenges were opened with the recast of Energy Performance of Buildings Directive, requiring by 2020 that new buildings be “nearly Zero-Energy Buildings” (nearly ZEB). In addition to consumer buildings, Net ZEBs are also producers’ by using as much renewable energy sources as possible to compensate the building energy load. Sustainable cities require energy-efficient buildings, i.e. buildings where the use of energy is minimized without compromising the occupants comfort, namely for heating, cooling, lighting and indoor air quality. But smart cities require energy-efficient ‘interactive’ buildings, which integrate multiplecarrier energy networks and provide up-to-date valuable information for their management, where buildings are simplified to single nodes characterized by their energy load, generation, storage and conversion, applying the load-generation approach. The information currently available in the Energy Performance Certificate is not relevant for estimating the time dependent building energy load, but it can be easily improved by including a few descriptive parameters

Methodological development of sesonal cooling energy needs by introducing ground-cooling systems

In past years, building professionals increased their interest on passive systems as sustainable solutions to reduce energy needs. This has been driven by the building certification program and new Portuguese building thermal code enacted in 2006. For residential and small office buildings, the methodology adopted is a seasonal quasi-stationary approach for calculating cooling energy following EN ISO 13790:2007. However, this method lacks specific recommendations for accounting passive cooling systems, namely ground-cooling systems. In this paper, the ground-heat exchanger contribution is included in the energy needs method. This development is sustained by measurements obtained in the ground-heat exchanger running on Solar XXI office building at LNEG campus, complemented by simplified and Fourier theoretical formulations. The horizontal ground-heat exchanger at Solar XXI is constituted by 32 concrete ducts, with a 30 cm diameter and buried 4.6 m deep. The air entrance is made from a feeding well about 15 m away from the building and its functioning during summer warm days supplies cool air for room offices

Thermal performance of residential buildings with large glazing areas temperature climate

This 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

Thermal performance of residential buildings in Lisbon with large glazing areas

This work presents the results of an experimental study of residential buildings (multi-family apartments) with glazing areas greater than 75% of the total façade area, and for different solar exposures in Lisbon. These buildings were designed after the implementation of the first Portuguese Buildings Thermal Regulation and they are intrinsically related with the construction and architecture practiced in the last few years. The analysis includes the thermal behaviour of the apartments selected for the study during the summer (2007) and winter (2007-2008). During the monitoring process important data were obtained to assist in the understanding of the thermal performance of the observed units. The main thermal exchanges in a building generally take place through the transparent elements and these can be considered an element of great flexibility and adaptation to climatic variations. The mean of the interior temperature means in the different monitored compartments during the hot season was approximately 27ºC (some cases close to 29ºC), while in the cold season 21ºC (some cases close to 18ºC)