Environmental Design Sourcebook

Innovative Ideas for a Sustainable Built Environment

William McLean, Pete Silver

• Editore: RIBA Publishing
• Anno: 2021
• ISBN:
  9781000408997
• Edizione: 1
• Argomento: Arquitectura
• Categoria: Sostenibilidad en la arquitectura

How do we design in a climate emergency? A new social and ecological prerogative demands appropriate material choices, a re-invention of construction and evolving building programmes that look at lifecycle, embodied energy and energy use. Highly illustrated with practical information and simple explanations for design ideas, this book is the perfect introduction to sustainable design for architecture students. It presents key concepts in relation to the embodied energy of construction, material properties and environmental performance of buildings in an accessible way. In explaining the principles and technologies by which we heat, cool, moderate and mitigate, it demystifies environmental design as a technical exercise and enables students to create sustainable buildings with impact. Keep this sourcebook with you. Features: Amphibious House (Baca Architects), Ashen Cabin (HANNAH), Bunhill 2 Energy Centre (Ramboll, Cullinan Studio, McGurk Architects and Colloide), Cork House (Matthew Barnett Howland, Oliver Wilton and Dido Milne), Dymaxion House (Richard Buckminster Fuller), Eastgate Centre (Mick Pearce), Neuron Pod (Will Alsop – aLL Design and AKT II), Quik House (Adam Kalkin) and Tension Pavilion (StructureMode and Weber Industries). Covers: Acoustics, bamboo construction, biopolymer, bioremediation, CLT, climatic envelope, computational fluid dynamics, earthen architecture, fabric formwork, hempcrete, insulation, mycelium biofabrication, paper construction, passive solar heating, pneumatic structures, solar geometry, tensegrity structures, thermal mass and more.

Chapter 1
Climate and Human Comfort

DOI: 10.4324/9781003189046-1

‘Health should be at the forefront of the architecture curriculum, as the driver for sustainable design.’⁵

Beth Bennett-Britton

The environmental factors that provide the necessary conditions for human comfort and survival are quite specific, and define a narrow set of upper and lower temperature and humidity levels. Humankind’s imperative, by choice or otherwise, to live across the globe in a range of climatically challenging locales, in pursuit of food and work, is proof of both human ingenuity and local adaptation. The environmental designer and campaigner John-Paul Frazer used to give a talk for undergraduate students entitled ‘Learning from the Locals’,⁶ in which he described the insects, animals and plants that could survive in extreme heat or coolth. Frazer would explain the processes by which a beetle might condense water on its wings in a waterless desert, or a prairie dog would regulate the temperature of its complex network of burrows through careful siting (elevation and orientation). Frazer’s point was that we should study local adaptation in nature, and that if we extend that study to include local (vernacular) architecture we would build a greater understanding of how to work with our local environment to achieve human comfort through dynamic and symbiotic design and construction. The relatively new branch of engineering known as biomimetics provides design solutions that are inspired by, but do not copy, nature.

The following chapter outlines key areas of environmental design science that begin with the operational details of human comfort. It describes conditions critical for human survival as well as conditions desirable for human comfort, for which the designer should strive. Solar geometry is explained in simple diagrammatic terms, but is common to all technologies and designs featured throughout this book. All our energy comes directly or indirectly from the sun. Wind and acoustics are discussed as environmental factors that we can harness, mitigate and tune for our comfort and pleasure, as are thermal mass and insulation, which we can employ to regulate the temperature of our buildings. Harold Hay, who is quoted in this chapter, undertook fascinating research into dynamic thermal mass and insulation, and how we might change and deploy these properties as required. It is important that designers continue to question the assumptions and received wisdom of construction knowledge and building performance.

The climate zones as defined by the Köppen–Geiger map help to classify climatic regions and can provide designers with a ‘rule of thumb’ for passive design measures, but we must remember that climate is dynamic and now more than ever is subject to change. The psychrometric chart graphically situates an ideal temperature and humidity for our basic comfort, but interestingly this ‘comfort envelope’ can be extended with simple passive measures such as local shade or breeze, and this less hermetic and more dynamic view of thermal comfort has the potential to reduce both the embodied energy and energy in use of architecture. Computational fluid dynamic (CFD) software was until recently the domain of the engineering specialist, but with its relative ubiquity and likewise the augmented reality of solar geometry phone apps, we now have at our fingertips powerful analytical ‘design’ tools that we should usefully employ.

Fig 1.02.5 Diagram showing relative scale (but not distance) relationship between the sun and the earth (in blue). The diameter of earth at the equator is 12,756 kilometres and the diameter of the sun is 1,392,700 kilometres (over 109 times larger).

1.01 Human Comfort

‘Alliesthesia helps explain certain aspects of comfort under transient conditions, like the anticipatory effect on sensation and comfort following moving from one set of thermal conditions to another.’⁷

–Asit Mishra, et al.

Human comfort is chiefly dependent on thermal comfort and maintaining the body at an acceptable temperature. Through the process of thermoregulation, our core body temperature remains at a relatively constant 36.5–37.5°C. When we are too hot we lose heat mainly through the evaporation of sweat (perspiration), but when humidity levels are very high (above 80%) evaporation rates drop and our ability to cool ourselves is radically reduced. For human comfort, relative humidity should be between 40 and 70%. When we are too cold our bodies start to shiver, which increases body heat and we also get ‘goose bumps’, created when muscles at the base of each body hair contract and pull the hair upright, trapping air next to the skin to create a layer of thermal insulation. As humans have lost most of their body hair, the reflex is now largely obsolete and we depend on clothing or buildings to maintain our comfort. We can locally mitigate the effects of heat with simple measures such as a breeze from a window or fan; local air movement of 0.5 metres per second can provide an equivalent temperature reduction of around 3°C.

Alliesthesia describes a kind of thermal pleasure derived from ideas of adaptive comfort in buildings, which might afford pleasant thermal changes or differentiation throughout a building related to specific functional requirements such as sleeping or eating. Local lighting levels can also be a personal and subjective issue. It is not advisable for designers to apply generic standards to the provision of servicing in buildings, as this has a financial and environmental cost and does not necessarily support or enhance human comfort. Professor Andy Ford stated that ‘the relationship between numbers and human comfort has to be made meaningful, or it will be seen as boring’,⁸ which is a valuable provocation to urge designers to verify numeric data against personal experience and judgement. Other environmental factors key to maintaining and improving conditions critical for human comfort are:

• good air quality, and ensuring the supply of clean air within enclosed spaces
• illumination, and the provision of adequate daylighting and light levels
• good acoustics, for clarity of communication and protection from unwanted noise pollution from neighbouring rooms, buildings and the wider environment
• sanitation, for clean water supply and waste disposal.

There is an increasing focus on the provenance of construction materials and their relative toxicity in relation to the ‘off-gassing’ of volatile organic compounds (VOCs) contained in synthetic materials and finishes, which can be obviated or eliminated through the use of environmentally benign alternatives.

Fig 1.01.1 A thermal image or thermogram captures the long-infrared frequencies of the electromagnetic spectrum, so can visualise temperature. This increasingly ubiquitous technology (used to diagnose Covid-19 at airports) can be used to accurately measure human temperature as well as the relative thermal insulative performance of building fabric – or how much heat a wall traps or emits.

1.02 Solar Geometry

‘A well-conceived and constructed building will interact positively with the local climate during its entire lifetime, thus minimizing its dependency on non-renewable resources.’⁹

– Livia Tirone

The earth orbits the sun in an anticlockwise elliptical orbit once every 365.26 days. It spins anticlockwise on its north–south axis once every day, which explains why the sun appears in the east and disappears in the west. The earth’s axis is tilted with respect to the plane of its orbit at an angle of about 23.4 degrees, known as the ecliptic. This tilt (or ecliptic plane) means that for half of the year the north side of the earth is tilted towards the sun and the south is tilted away and, for the other half of the year, the reverse is true.

The equatorial plane divides the earth into the northern and southern hemispheres. The intersection of the equatorial and ecliptic planes is called the line of equinoxes. At two points in the earth’s orbit this line intersects the sun, marking (in the northern hemisphere) the start of spring (20 March) or autumn (20 September). Perpendicular to the line of equinoxes is a line which contains the solstices, and when the northern hemisphere is most tilted towards the sun, it marks the longest day of the year (summer solstice, June 21) while the southern hemisphere has its winter solstice, and vice versa with the shortest day of the year in the northern hemisphere (winter solstice, 21 December).

The average distance from the earth to the sun is around 150 million kilometres (93 million miles), and writer H.G. Wells explains their relative distance and dimensions: ‘… If, then, we represent our earth as a little ball of one inch [24.5 mm] diameter, the sun would be a big globe nine feet [2.74 m] across and 323 yards [295 m] away, that is about a fifth of a mile [a third of a km], four or five minutes’ walking’.¹⁰ The diameter of earth at the equator is 12,756 kilometres and the diameter of the sun is 1,392,700 kilometres (over 109 times larger), which helps to explain why sunlight can be described as parallel rays, due to the sheer size of the sun in relation to the earth. When experimenting with small physical design models, it is worth remembering that the light of a desk lamp is not collimated (or parallel), so if the sky is clear (and you can determine which way is north) then it is always advisable to test sun-path modelling and shadow-casting in the open air. As Buckminster Fuller exclaimed, ‘The most important thing to teach your children is that the sun does not rise and set. It is the Earth that revolves around the sun’.¹¹

Fig 1.02.1 Ernő Goldfinger posing with a solar inclinometer for measuring sun angles.

Fig 1.02.2 Three ‘blinkered mirror’ solar structures with guest critic Ted Cullinan. Studio in the Woods workshop, Isle of Wight, 2010.

Fig 1.02.3 Detail of mirror structur...