Elena G. Dascalaki

Energy conservation and retrofitting potential in Hellenic hotels

Abstract Energy consumption data from 158 Hellenic hotels and estimated energy savings that result from the use of practical retrofitting techniques, materials and new energy efficient systems are presented. The data were collected during an extensive energy audit of buildings that was carried out in Hellas, within the frame of a National Energy Programme sponsored by the CEC VALOREN Programme, for energy conservation in buildings. During this short monitoring campaign and on-site visits of a trained panel of engineers to each building, all information related to the buildings construction, heating, cooling and lighting systems, and all other mechanical and electrical systems, was collected. The main results and energy characteristics of cooling, heating and lighting on energy consumption and performance are discussed. The annual average total energy consumption in hotels is 273 kWh/m2, one of the highest among all categories of buildings. Several scenarios for possible interventions to the buildings outer envelope, heating, cooling and lighting systems are proposed and evaluated, in order to assess the effectiveness of various energy conservation techniques. Based on the results from several simulations, it is concluded that it is possible to reach an overall 20% energy conservation.

ORME : A multicriteria rating methodology for buildings

Abstract To check the compliance of a building with regulations, evaluate the efficiency of retrofit, or even label a building one would in most cases perform a comparison of a number of building qualities. Within the framework of the European Joule–Thermie OFFICE project, a multicriteria rating methodology was developed for this purpose, based on a rating method that uses principal component analysis, and a ranking method that uses a partial aggregation technique. The aim of this methodology is to rate or to rank office buildings and retrofit scenarios of the same building according to an extended list of parameters, including: • energy use for heating, cooling and other appliances, • impact on external environment, • indoor environment quality, • cost. The paper presents the principles used in the methodology, and some examples of application to actual buildings. More information is given in a complete report (ORME—Office building rating methodology for Europe, Office Project Report, University of Athens, 1999).

On the combination of air velocity and flow measurements in single sided natural ventilation configurations

Abstract Single sided natural ventilation configurations are very frequent especially in buildings in urban environments. Four single sided ventilation experiments were carried out in a full scale outdoor Test Cell facility. Air velocity measurements were taken at various heights in the middle of the opening. The average air flow rate through the opening was derived using the tracer gas decay technique. This work presents the results of an investigation into the relationship between the air velocity at the opening and the bulk air flow rate measurements. The paper presents a description of the experimental set-up as well as a qualitative discussion of the results.

Energy characteristics and savings potential in office buildings

The present paper reports the findings of a monitoring campaign in 186 office buildings in Greece. The specific energy consumption of the buildings for heating, cooling, and lighting purposes, as well as the consumption of the office equipment is reported. The impact of the used systems, techniques, and components is investigated. The potential and the limitations of various energy conservation systems and alternative techniques is assessed. The present study provides useful information for efficient energy planning, as well as appropriate design and equipment selection, in office buildings.

Predicting single sided natural ventilation rates in buildings

Natural ventilation contributes significantly in reducing the cooling load of buildings and in increasing thermal comfort. Single sided natural ventilation configurations are very frequent especially in urban environments. Fifty-two single sided natural ventilation configurations have been studied experimentally and are compared with the predictions of six different network ventilation models. The heat and mass transfer characteristics of the studied cases are analysed and discussed. Finally, a new model to predict air flow rates in single sided natural ventilation configurations is proposed.

On the potential of retrofitting scenarios for offices

Abstract Within the framework of OFFICE research project the energy conservation potential of combined retrofitting actions was investigated for five building types in four different climatic regions in the European continent. The studied actions involve interventions on the building envelope, HVAC and artificial lighting systems as well as integration of passive components for heating and cooling. Interventions affecting the performance of the building in the global aspect were also assessed. The potential of retrofitting actions proposed for each building type was assessed through energy simulations using high-accuracy computer models and climatic data from 10 locations in South Mediterranean, Continental, Mid-Coastal and North Coastal Europe. Analysis of the results revealed common trends in the energy performance of different building types and permitted to extract information on the most suitable retrofitting interventions in each.

Passive retrofitting of office buildings to improve their energy performance and indoor environment: the OFFICE project

OFFICE was a research project, partly funded by the CEC, dealing with the passive retrofitting of office buildings to improve their energy performance and indoor working conditions. The project was coordinated by the University of Athens with the participation of organizations and research institutes from eight European countries. The aim of the project was to develop global retrofitting strategies, tools and design guidelines in order to promote successful and cost-effective implementation of passive solar and energy efficient retrofitting measures to office buildings. Within the frame of the project, 10 office buildings located in different climatic zones around Europe were studied extensively. Energy audits and monitoring activities, specific experiments as well as an assessment of the potential of proposed retrofitting scenarios were performed for each building. The final deliverables of the project include: (a) case studies presenting high-quality examples of representative retrofitted office buildings in various parts of Europe; (b) a rating methodology classifying office buildings according to their energy consumption, CO2 production and indoor thermal and visual comfort; (c) an Atlas describing the technical and economical potential for energy conservation of selected retrofitting scenarios for defined types of office buildings in different climatic zones of Europe and (d) Design Guidelines, performance criteria and methodologies for best practice giving credit for renewable energy sources incorporated into office buildings, all presented in the form of a Handbook. Results from the assessment of the potential of various retrofitting scenarios proposed for each case study are included in the Handbook in the form of brochures. This paper gives an analytical description of the activities carried out within the frame of the project and describes the resulting final deliverables.

Energy consumption and the potential for energy conservation in school buildings in Hellas

School buildings (238) in Hellas were audited for construction, heating, cooling, lighting, and mechanical and electrical systems. The annual average total energy consumption is 93 kWh/m2, of which approximately 72% is consumed for space heating. The assessment of various energy-conservation techniques shows a potential for 20% overall energy conservation.

Natural convection heat transfer coefficients from vertical and horizontal surfaces for building applications

Correlations for natural convection heat transfer coefficients from experimental studies are reviewed and compared for their applicability to real surfaces in buildings. All correlations have been modified for appropriate Prandtl and Grashof numbers in building applications. A comparative statistical analysis reveals that there is a good agreement between the available correlations.

Modeling large openings with COMIS

Conjunction of Multizone Infiltration Specialists (COMIS) is a model that can be used to simulate air flow and pollutant patterns in a multizone structure. Experimental data from air flow measurements in single sided naturally ventilated spaces, common in urban environments, and from cross-ventilated spaces, are compared against predictions from COMIS. The single sided ventilation experiments were performed in a full scale building and a test cell, which led to the definition of a correction factor for COMIS. Cross-ventilation experiments were performed in two zones of a full scale building. Results from both experimental and calculated data using COMIS were in good agreement.