20-05-2013, 03:42 PM
An Energy Conservation Architectural Design Tool for Warm Climate (LTV): The tool development and testing.
An Energy Conservation.pdf (Size: 145.06 KB / Downloads: 49)
ABSTRACT
The use of design tools in architectural design is common place. Yet, in recent years the need has arisen to
provide design tools to assist with the evaluating the energy usage of buildings. A number of tools are available
for this type of work. Unfortunately, many of these tools are inappropriate for integration in the architectural
design process. The research described here reports development work on a lighting, thermal and ventilation tool
for use at the conceptual stage in the design process. The main contention is that this type of tool is crucial to
effective passive low-energy design as it is difficult to integrate energy saving feature at later stages in the design
process. Part of this work has necessitated a critique of the concept of the passive strategies for non-domestic
buildings; this is an important element in assessing the energy contribution of the external environment to the
building.
INTRODUCTION
Research work has been underway to develop a design tool for assessing the environmental impacts of nondomestic
buildings. In this case energy -use is taken as an indicator of environmental impact.
This tool is called the Lighting Thermal and Ventilation (LTV) architectural design tool (1). It models the energy
consequences of using climate responsive design strategies in the building design. Yet the question arises as to
the form this tool should take for it to be most effective for giving architects feedback of the consequences of the
building design on energy consumption. It is argued here that the key to this question lies in the design process.
It is widely acknowledged that ‘the best opportunity for improving a building’s energy performance occurs early
in the design process when basic decisions are made (2).’
Moreover, the penalty for not addressing climatic responsive design issues early in the process is that
‘opportunity will be lost to make significant savings by relatively simple adjustments to the design. Increasingly
sophisticated or costly efforts are needed to save energy (2).
A number of phases can be determined, the phase that is of most interest is the conceptual design stage where
basic climatic responsive strategies are used. In large commercial non-domestic buildings this involves the
conceptual layout and thermal zoning of the building.
Thermal zoning is a key concept in assessing the thermal response of the building. It is the relation of the spatial
organization of the building to the exposure to environmental factors. Thermal zoning is the subdivision of
spaces inside the building that have varying thermal temperatures. Zones vary with orientation and with exposure
to environmental conditions. A common nomenclature in cool climates is to use two main zones, the passive
and non-passive (active) zone. ‘Passive zones can be day lit and naturally ventilated and make use of solar gain for
heating. Non-passive zones have to be artificially lit and ventilated (3). The importance of this description is that
passive zones use less energy due the use of natural energy than non-passive zones, which use man-made energy
ie, electrical energy. Therefore a basic climate responsive planning stage at the conceptual stage is to make this
passive zone as large as possible to reduce energy consumption.
Climate responsive design strategies
A review of the passive, low energy design principles used in non-domestic buildings revealed the following
factors important in warm climates. These are framed as design strategies that can be used by architects to reduce
energy consumption. .
For the purpose of the study these strategies are used as variables that can be manipulated in a work-back process.
This involves generating a number of possible design scenarios an architect may take and find the energy
consequences. Architects tend to evaluate design concepts in terms of the plan and section of the building.
A hierarchy is found in the decision making process which relates to priorities designers have in the design
process. For convenience, first order decisions are those that relate more to the planning decisions whilst second
order are those in the section.
Solar shading
The first variable to be considered was solar shading .As shown in Figure 2 supposed the variable in this study is
the angle between a horizontal plane and the line that links the base of window and the extreme of the shading
overhang.
The shading overhang width for the different shadow angles are shown is the Table 2. Note that this is a
theoretical study, small shadow angles give impractical overhang widths.
The designer has a number of choices in the design of façade, one is the location of the window another is the
window to wall ratio (WWR), that is the percentage of transparency to solidity. A number of additional
assumptions were made regarding nature of the test cell used for the study with regard to these choices..