Edna Shaviv

Thermal mass and night ventilation as passive cooling design strategy

We calculated the influence of thermal mass and night ventilation on the maximum indoor temperature in summer. The results for different locations in the hot humid climate of Israel are presented and analyzed. The maximum indoor temperature depends linearly on the temperature difference between day and night at the site. The fit can be applied as a tool to predict from the temperature swing of the location the maximum indoor temperature decrease due to the thermal mass and night ventilation. Consequently, the fit can be implemented as a simple design tool to present the reduction in indoor temperature due to the amount of the thermal mass and the rate of night ventilation, without using an hourly simulation model. Moreover, this design tool is able to provide for the designer in the early design stages the conditions when night ventilation and thermal mass are effective as passive cooling design strategy.

Shading: A design tool for analyzing mutual shading between buildings

Abstract A method and a model for analyzing visually and quantitatively mutual shading between buildings is presented. The method allows fast and efficient calculation of the ratio between insolated and total surface areas of any given examined object that is shaded by other irregular and nonplanar elements. The calculation of this ratio is carried out for all the months and hours for which either shading or insolation is required. The information obtained may serve as hourly input data for any dynamic simulation model which evaluates the thermal performance of the different external or internal shading systems. For a visual and a qualitative evaluation of the shadows among buildings, the suggested model permits a very realistic representation, in which the light source is defined according to the azimuth and the altitude of the sun at the particular time of examination. The self shading and brightness of the different surfaces and the shadows cast by the different elements at the designated time are then generated and can be evaluated visually. The method is demonstrated by a case study.

On the use of ‘solar volume’ for determining the urban fabric

Abstract An exhaustive analysis for the determination of the urban fabric is carried out by implementing a computerized model SustArc. The model evaluates the maximum allowed ‘solar volume’ to be built without preventing solar access from each building and from the open spaces during a predefined period of the year. For every urban configuration, the model calculates the obtained urban density. The results show that it is possible to achieve high density urban quarters without violating any solar rights. Optimized urban fabric solutions are presented.

Climatic aspects in urban design—a case study

We present a case study of a design of a new business district in Tel Aviv city. In this work climatic aspects were taken into consideration in the very early design stages. For that purpose, two models SustArc (Proceedings of the ISES 1997 Solar World Congress, Taejon, Korea, 1997, p. 148) and FLUENT 5.0.2 (Fluents Users Guide, Fluent Inc., NH, USA, 1999) were applied in order to achieve solar and wind rights. The new business district was designed as a high-density urban area and is located near an old low-rise residential quarter. SustArc was used as a design tool to create the solar envelope that shows the maximum available volume in which it is possible to build without violating the solar rights of existing residential neighborhood, the main avenues and the pedestrian sidewalks. FLUENT, on the other hand, was implemented as an evaluative tool, in a trial and error method, until a design solution could be achieved, in which the wind rights of the residential neighborhood were preserved, while ensuring tolerable winds inside the business district. The paper presents the process of sun and wind controlled planning, as well as the recommendations.

Evaluation of Urban Surface Energy Fluxes Using an Open-Air Scale Model

Abstract The thermal behavior of an urban surface is crucial to understand, but it is difficult to predict using conventional measurement or modeling approaches. In this study, an integrated method is proposed for evaluating urban energy exchanges with an open-air scale model of a building–street canyon surface array. The technique, which potentially combines the flexibility of modeling with the reliability of empirical observation under natural turbulence and radiative loading, is tested in hot, arid summer conditions to gauge its ability for reproducing surface–atmosphere energy fluxes that are representative of diurnal patterns in actual urban settings. After identifying the inertial sublayer, which is created above the scaled roughness array at a point near its downwind edge, roughness parameters utilized in the calculation of turbulent sensible heat flux are determined for two different array configurations of varying frontal area density and compared with existing data from field studies and morphom...

Modelling the thermal performance of buildings

Abstract The mathematical model developed by Shaviv and Shaviv for predicting the thermal performance of full scale buildings is used to improve the design of a particular house. The climatological data needed for the calculations are described as well as other technical data. A case study is brought as a numerical example in which a particular design with architectural constraints is improved step by step so as to obtain thermal comfort in summer with minimal energy consumption.

Designing buildings for minimal energy consumption

Abstract A dynamic model for predicting the thermal behaviour and energy consumption of a full-scale building has been developed. The model can include most of the design and climatological factors affecting the building. The time-dependent equation for the heat flow through the walls is converted into an implicit scheme and solved numerically. Special effort has been devoted to producing a model capable of aiding the architect during the various steps of building design, so as to approach thermal comfort with minimal energy consumption. The results are presented in graphical form, which allows the architect to detect easily the crucial factors in the thermal performance of the building.

Analyzing mutual shading among buildings

A method for evaluating solar rights and shading requirements in an urban environment is presented. The method is embedded in a CAD tool developed and adapted for this purpose. With this tool one can analyze the mutual shading between buildings and other objects like trees. The purpose of this CAD tool is to allow the designer to plan efficiently the various functions of spaces among different structures, like buildings, as well as determining the location of the passive and active solar collectors. The method is a general one and allows a fast and efficient calculation of the ratio between insolated and total surface areas of any given examined object that is shaded by other irregular and nonplanar elements. The calculation of this ratio is carried out for all the months and hours for which either shading or insolation is required. The information obtained may serve as hourly input data for any dynamic simulation model which evaluates the thermal performance of the different external or internal shading systems. For a visual and a qualitative evaluation of the shadows among buildings, the suggested model permits a very realistic representation, in which the light source is defined according to the azimuth and the altitude of the Sun at the particular time of examination. The self shading and brightness of the different surfaces and the shadows cast by the various elements at the designated time are then generated and can be evaluated visually.

Representing and solving the automated building design problem

The problem of automated building design is considered. A new graph-theory based model is suggested for representing and solving the problem. The model is embodied in a detailed algorithm for generating floorplans that meet specified constraints. A prototype system based on this algorithm has produced accurate building plans that are comparable to those designed by (human) architects.

Simulations and knowledge-based computer-aided architectural design (CAAD) systems for passive and low energy architecture

Abstract This paper describes a methodology for supporting computationally all phases of an energy-conscious design and evaluation process, by combining procedural simulation and knowledge-based heuristic methods in one integrated system. Based on this methodology knowledge-based computer-aided architectural design systems for the design and evaluation of solar and low-energy buildings are presented. The knowledge-base contains the heuristic rules for the design of passive solar buildings. Whenever possible, the knowledge-base guides the designer through the decision-making process. Yet, if the rules of thumb are not acceptable for the particular design problem, the knowledge-based system guides the architect by using procedural simulation models.