101 Rules of Thumb for Low Energy Architecture

Huw Heywood

• Publisher: RIBA Publishing
• Year: 2019
• ISBN:
  9781000705096
• Edition: 1
• Topic: Arquitectura
• Subtopic: Arquitectura general

101 Rules of Thumb sets out the essential elements of low energy architecture in a fresh, intuitive way.

In an area where ever-changing technology and complex legislation and can cloud the designer's thought-processes, this book encourages the designer to think clearly and intuitively about the fundamentals of low energy buildings.

With reliable, simple rules of thumb that will provide new ideas and refresh the designer's palette, each page focuses on a single piece of advice or guidance along with a clear hand-drawn illustration, while there are also plenty of tips and more detailed information for those who wish to dig deeper. The emphasis is on passive low-energy principles, and the rules of thumb cover all the design fundamentals from site and location to orientation and form, peppered with some which will help the designer to think 'outside the box' about the design process itself.

Chapter 1
Working with Site and Location

• Sun and shade
• Climate and micro-climate
• Shelter from wind and rain

Rule 1. Buildings Use Half the World’s Energy

We use half of all the energy we generate in the world, much of which is created by the burning of fossil fuels, to run our buildings. Add transport to and from those buildings, and designers of the built environment have some control over, and responsibility for, 75% of global energy use.

Rule 2. Think before You Build

Buildings last an age and consume energy throughout their lives, so whether to build or not to build is a big question. The answer might be to refurbish, reorganise, change business strategy or change your life rather than to build something new, and this might be the lowest long-term energy-use solution. Consider all options.

Rule 3. The Sun Rises in the East and Sets in the West

It is worth reminding ourselves of this most basic rule. However, it is also worth remembering that, even outside the equatorial regions, in the mid-latitudes of the northern hemisphere winter the sun rises south of east and in the summer it rises north of east. This means that in summer the north face of a building in these regions might be very briefly exposed to the sun, but in the winter the sun will never warm that building’s northern face. In the northern hemisphere, after rising, the sun will be seen traversing across the sky in the south. The reverse is true south of the equator.

Rule 4. The Height of the Sun above the Horizon Determines Many Aspects of a Climate-Responsive Architecture

In December the highest altitude of the sun above the horizon at midday in London is around 15°. This angle varies according to latitude, and that is part of what makes every individual location on earth unique. The diagram gives December sun angles for cities around the world. Using sun-path diagrams or simple-to-use web-based calculators, the position of the sun at any time of day or any time of the year can be found out. Knowing the relative position of earth and sun, or solar geometry, is an important aspect of climate-responsive architecture.

Rule 5. The Sun’s Rays Turn to Heat on Contact with Any Surface

The way this happens is rooted in quantum mechanics, but the simple result is that the earth, and everything on it, is warmed by the sun, making all life possible. The heating of the earth also results in climate and weather, which vary greatly depending upon where we are on the planet.

Rule 6. If You do Not Want Heat inside, Keep the Sun out

Just as the earth is warmed by the sun, so is any other surface that the sun’s rays reach. This is an important rule because if you are trying to avoid overheating in a building you must prevent direct sunlight from entering: once direct sunlight has entered a building, it’s too late to stop it becoming heat.

Rule 7. Harness the Power of the Low Winter Sun – it is a Free Source of Heat

In the winter the sun is low in the sky, so the sun can penetrate deep into a space, if it is allowed to, bringing free heat with it.

Rule 8. Prevent Overheating in Summer

In the summer the sun is high in the sky, reaching, in June, a maximum angle of about 62° above the horizon in London, 73° in both Beijing and New York, and 83° in Cairo. In Sydney in December the sun reaches about 80° above the horizon. For solar-oriented windows a simple, external horizontal shading device can prevent this high-angle summer sun from entering a building. Rule-of-thumb depths of projection from near the head of a window are: 600–900mm deep in the mid-latitudes; and at least 1,200mm deep close to the equator, where a combination of vertical and horizontal projections should be employed.

Rule 9. Site Topography Informs Us about Building Location

Topography, the form of the land, must be studied before you begin to design. Wind direction and intensity are affected by hills, valleys and other natural features. Often, in valleys and mountainous terrain the wind patterns change between day and night. The direction of the wind might be read in the direction in which grasses have been blown on a site.

Rule 10. A Windbreak will Halve the Wind Speed and Lead to Reduced Cooling of the Building Envelope

A windbreak, or shelter belt, will significa...