BUILDING ENVELOPE

The role of building envelope in reducing energy consumption in hot environment

Table of Contents

Chapter # 1: Introduction3

Ch # 2: Literature Review6

The solar envelopes12

The Solar Collection Envelope13

The determination of the Solar Collection Envelope14

Ch # 3: Envelop Building and Energy Consumption17

Performance based design17

Modeling the building shape using the Solar Collection Envelope19

Energy performance simulation23

Variation of the SCE for different facade orientation28

Summary30

References31

Chapter # 1: Introduction

During the preliminary stages of a building's design, the architect deals with the general geometrical factors related to the building's shape. These factors include the building's height in relation to street dimensions, facade orientation and the building's proportions. In these early stages, the solar potential of the building and the surrounding areas are determined, assuring the exposure of the elevations and sidewalks to the winter sun, and creating the appropriate shading during the critical hours of the summer days. The designer can check these issues using sun diagrams or manual protractors. However, using a computer tool has several advantages: (a) using such a tool is easy and fast, therefore it is possible to study and evaluate several design alternatives for building orientation and geometry; (b) the model can be used for any geographical location; (c) the determination of the critical date and time is not an easy task, especially when the building plan is not rectangular and is rotated from the north-south axis (see, for example, Fig. 10 in Section 6), using the computer model this process is done automatically; and (d) it is possible to use the tool for educational purposes, in order to understand the relations between sun movement, building geometry and performance.

There are several examples where designers tried to shape buildings in a way that enhances their thermal performance. This was done by determining the building's form in a manner allowing both, partial self-protection from solar radiation during a required period, as well as its insolation in winter in order to achieve passive heating of the building.

Examples of such buildings are the Bank of Israel in Jerusalem (A. and E. Sharon Architects), the Blue Cross and Blue Shield of Connecticut Building in north Haven, Connecticut (Ellenzweig Associates Inc.) and the city hall buildings of Bat Yam (Hecker, Sharon, Neuman), Boston (Kallmann, McKinnel, Knowles) and Tempe (Michael and Kemper Goodwin). The last example is rotated by 45° from the north-south axis. In these examples, an upside-down pyramidal shaped structure was created so as to achieve self-shaded facades during a certain period in summer.

It must be stated that a building with an inverted pyramidal geometry may increase its roof area as in the Tempe city hall. Therefore, additional design solutions should be considered, avoiding very inclined walls, such as the use of deep windows as proposed in the Bank of Israel building (see Fig. 4). In this example, the combination of sloped walls with deep windows avoids the need for a greater window's depth. The depth as proposed in the Bank of Israel is also appropriate for the placement of shelves under the ...