Cover Image
close this bookDesign Handbook on Passive Solar Heating and Natural Cooling (HABITAT, 1990, 162 p.)
close this folderIntroduction
View the documentA. The design process
View the documentB. Site investigation
View the documentC. Relating the brief to the site
View the documentD. Schematic design stage
View the documentE. Detailed design stage
View the documentF. An outline to this publication

A. The design process

The design process is a complex. deliberate set of acts In which the designer aims to bring together, as a whole, a balance of all aspects of the problem to produce a solution. The climate, the energy use and the thermal comfort needs of the end-user are Just some of the inputs to the process. The focus of this publication is specifically on these aspects whilst still considering the other aspects of the whole such as shelter, durability, and appropriateness. The most important goal must be to aim for a balance of all these as good architecture is the product of such a balance.

The use of the sun and climate for thermal comfort and energy efficiency is as important a part of the whole design as is the structural design or indeed the design of the spaces themselves.

Some aspects of thermal design are both very simple and fundamental to a successful solution, others are more complex and require detailed calculation to fine-tune them and produce the most economically efficient result. In many instances where the building is a "one-off" design, the refinement of the building economics may be less important than, say. the method of construction for an owner-built design or the visual finishes of a prestige building. In such cases it is often not necessary to refine the thermal design thoroughly with extensive and detailed calculation.

In cases where a design is to be reused many times or the building is a prototype for further development, comprehensive design analysis is most important. The savings that will accrue from the reuse of the design work will be extremely beneficial to the community involved.

Before finalizing a design brief it is important to understand the social. cultural and climatic context of the proposed building. The first two can usually be established through careful consultation with the client(s) whilst the climatic context must be established by the designer from a knowledge and/or investigation of the site.

Most of the populated areas of Australia are located in what might be called a "summer driven climate", i.e.. warmer weather occupies the major part of the year. There are a few exceptions to this: mainly Tasmania, and the high altitude country of the Australian Alps and the Southern and Northern Tablelands along the East Coast.

Whilst designing for year-round comfort it is important to pay particular attention to the design for the more dominant season. In most of the Australian domestic sector, winter space heating consumes more energy than space cooling because a relatively small percentage of homes have full air conditioning. In some of the hotter climates, however, the situation is changing. Where the summers are hot and humidity levels are low, evaporative cooling is used extensively. These units require a ready supply of clean water, but are relatively tow energy users. In the more humid hot areas reverse-cycle air conditioning is the only choice.

Electricity marketing bodies throughout Australia are promoting the use of heat pumps for space heating because their coefficient of performance (COP) makes this form of heating competitive with natural gas. However, for a small additional cost, these units can be purchased as full reverse-cycle air-conditioning units, thus providing a readily available cooling system for the summer months. This trend will help to increase the overall energy consumption (especially in summer) and raise expectations of thermal comfort. The penalty to the consumer in the short term is increased living costs. whilst to the environment the increasing demand for electricity (generated from burning coal) will only serve to accelerate the growing problems of the global greenhouse effect.

The integration of good thermal design into the whole design process is only possible if it is started at the beginning of the design process. Like the integration of structure into a design, it is rarely successful if applied after the event. At each stage of the design process there are appropriate considerations that must be taken and tests applied.

B. Site investigation

The first stage of the design process should be an analysis of the site in terms of the environmental, physical and legal considerations. The micro climate of the site, its access to sunlight and access to views are three major environmental considerations of an investigation of the site. Generally the temperature patterns on the site will be similar to those recorded in the district by the weather bureau, but the micro- wind patterns may vary somewhat according to surrounding obstructions such as buildings. trees and general topography. The summer afternoon breezes in a particular district might be from the northeast according to published data but on a particular site the direction might be changed by a small hill or grove of trees. The street pattern might deflect the wind and funnel it in another direction. A clear picture can only be obtained by visual inspection of the site. occupants can often be a useful source of information.

Before visiting the site, however, the designer should be familiar with the general climate of the district and have some idea of the appropriate design strategies for that climate, year-round. This is less of a problem where the designer lives in the district and has a first-hand knowledge of the climate of the area. The process known as "bioclimatic analysis" is especially useful where the designer is not totally familiar with the area (see chapter VI).

C. Relating the brief to the site

When establishing the brief with the clients, the designer should determine the thermal comfort needs of the intended users' building in terms of building use and occupants' activities. A building designed as a gymnasium, for example, should have a cooler Interior and perhaps better ventilation than an office space where the occupants are sedentary. Likewise a home for older people or a hospital environment should provide a more stable temperature environment, perhaps generally warmer in winter than the usual domestic environment. A custom-designed house provides an opportunity for the designer to match the thermal environment to the specific desires of the client.

D. Schematic design stage

Once the clients' brief is defined and the opportunities of the site are incorporated into that brief, drafting the schematic design can begin. First, specific zones or spaces in the building should be considered, with regard to their use, any view opportunities, inside/outside connections (both visual and physical) and winter sunlight utilization.

Then ventilation strategies for summer cooling as part of the building design are established. A clear cross-flow of cooling breezes is most important in areas where summers tend to be humid.

After this, windows are located and overall size criteria for view, daylight etc. are established. Rules of thumb are used to establish approximate sizes relative to room size and extent of thermal mass as discussed later.

The schematic design is then completed and a provisional selection of construction materials made. The schematic design should be tested using simplified methods such as graphs, nomograms or user-friendly computer models.

E. Detailed design stage

In the detailed design stage the designer is able to test all of the various elements of the building with a reasonable degree of precision. As the overall design is refined, so too should be the thermal design details such as insulation details, shading design and window design.

The external fabric design is tested for reduction of solar gains in summer and for control of conductive heat loss in winter.

External shading of openings is refined to control solar gains. Sunlight should be excluded from entering the building during certain times in order to minimize summer overheating. This is the time to determine the controlling factors in the design of shading devices (shadow cut-off angles, horizontal projections and heights above sills etc.), so that they provide the desired shade in summer and sun penetration In winter.

A final check of the north-glass area to the mass-area ratio can be made at this time using the evaluation techniques referred to above.

Construction details are developed for appropriate control of infiltration during winter and to prepare specification notes about construction quality control.

The final detailed design is tested using a suitable PC- computer-based thermal performance model such as CHEETAH, TEMPAL or ARCHIPAK.

F. An outline to this publication

The first five chapters of this publication take the reader through the basic design issues and establish the simple principles that are fundamental to good thermal design. Also included are appropriate "rule-of-thumb" guidelines for more specific use in the initial design.

The next chapter shows the designer how to evaluate the particular climate using the concept of "bio-climatic design". and thus how to choose between some of the basic design options discussed in the first chapter. This chapter addresses the problems of providing thermal comfort and improved lifestyle which, in many circumstances, is as important as the concepts of improved energy efficiency, especially where the basic energy consumption is low. Throughout history it has been found that improved thermal comfort and the entry of sunlight into northerly facing living spaces has a significant impact on the hearth general well-being of the occupants. This Is particularly so in cold winter climates where sunlit rooms are much more attractive than south-facing non-sunlit spaces.

Chapter VII investigates the detailed design using various tools and calculation procedures. It is in this section that the designer learns to refine the basic designs developed earlier. The calculation of detailed aspects such as shading for windows, energy-conservation measures and ventilation effects will be most important for prototype designs.

Evaluation and testing of a solution is important not only from the point of view of educational value but also simply to test the fitness of the design. With experience the designer will need to test design solutions less often as an intuitive design sense evolves.

Chapter VIII develops ways in which the proposed building's performance can be assessed.


Case studies have always been a valuable mechanism to bring a sense of reality to a design process. It is helpful to be able to study examples of buildings that are known to perform well and to see how and why they do so. It is also helpful to be able to see where certain strategies will produce limitations to the design in other ways. An example, perhaps, is the use of a thermal storage wall which, whilst energy-efficient and capable of producing a high level of comfort, might be too restrictive in terms of views to the north or visual connection to the outdoor spaces. In another situation or even another culture it might be ideal. The case studies included, as the final chapter of the handbook, strive to show these issues.

The annexes collect together a range of data appropriate to the Australian building designer. These should, by no means, be seen as exhaustive since the full range of useful data would require many volumes.