101 RULES OF THUMB FOR LOW ENERGY ARCHITECTURE

256 Pages·2021·9.961 MB·English

by  HUW HEYWOOD

2ND EDITION
101
RULES
OF
THUMB
For Low-Energy Architecture
HUW HEYWOOD
© RIBA Publishing, 2021
Published by RIBA Publishing, 66 Portland Place, London, W1B 1AD
ISBN 9781 85946 991 0
The right of Huw Heywood to be identifed as the Author of this Work has been asserted in
accordance with the Copyright, Designs and Patents Act 1988 sections 77 and 78.
All rights reserved. No part of this publication may be reproduced, stored in a retrieval
system, or transmited, in any form or by any means, electronic, mechanical,
photocopying, recording or otherwise, without prior permission of the copyright owner.
British Library Cataloguing-in-Publication Data
A catalogue record for this book is available from the British Library.
Commissioning Editor: Clare Holloway
Assistant Editor: Lizzy Silverton
Production: Sarah-Louise Deazley
Designed and typeset by Sarah-Louise Deazley
Printed and bound by W&G Baird
Cover image: Huw Heywood
While every efort has been made to check the accuracy and quality of the information
given in this publication, neither the Author nor the Publisher accept any responsibility for
the subsequent use of this information, for any errors or omissions that it may contain, or
for any misunderstandings arising from it.
www.ribapublishing.com
CONTENTS
DEDICATION AND ACKNOWLEDGEMENTS IV
PREFACE V
INTRODUCTION VI
CHAPTER 1. WORKING WITH SITE AND LOCATION 1
ʢ Sun and shade
ʢ Climate and microclimate
ʢ Shelter from wind and rain
CHAPTER 2. MANIPULATING ORIENTATION AND FORM 41
ʢ The relationship between sun and wind
ʢ The impact of building form
CHAPTER 3. THE LOW-ENERGY BUILDING ENVELOPE 71
ʢ Heavy and lightweight construction
ʢ The timing of heating needs
ʢ Reducing heat loss
CHAPTER 4. ENERGY AND THE INTERNAL ENVIRONMENT 111
ʢ Carbon-free heating: direct, isolated and indirect solar gain
ʢ Carbon-free cooling: using earth, wind and water
ʢ Carbon-free lighting: daylight
ʢ Colour
CHAPTER 5. RULES AND STRATEGIES FOR DIFFERENT 169
CLIMATIC REGIONS
ʢ Hot–dry climate
ʢ Hot–humid climate
ʢ Cold climate
ʢ Cold–winter/hot–summer climate
ʢ Temperate climate
NOTES, OBSERVATIONS AND REFERENCES – A NARRATIVE 182
BIBLIOGRAPHY
TOP TEN READS 232
BIBLIOGRAPHY 233
WEB-BASED RESOURCES 235
INDEX 241
DEDICATION
Dedicated to the memory of architect, teacher, colleague and friend
David Yearley.
ACKNOWLEDGEMENTS
I am most grateful to the superb team at RIBA Publishing, and
particularly to Commissioning Editor Clare Holloway, without
whose clarity about the point of a second edition it simply wouldn’t
have happened.
Many educators, authors, academics, practitioners, colleagues and
clients have been an infuence and have ofered wise advice over the
years, including those specialists who kindly gave feedback through
the process of manuscript review. I am beholden to them all.
My thanks once again go to James Scrace for his invaluable
contribution to the 101 Rules of Thumb books.
I continue to be indebted most to Bety for her patient ear and
astute suggestions.
IV 101 RULES OF THUMB FOR LOW-ENERGY ARCHITECTURE
PREFACE
This second edition has come about because the term low-energy
has become synonymous with the term low-carbon. The production
of energy generates nearly 75% of global greenhouse gas emissions,
the majority of those being previously buried CO from the burning of
2
fossil fuels, which is propelling us towards the 2°C warming safe limit.
The building sector is responsible for half of global energy usage and
40% of emited CO. By mid-century the world population is expected
2
to grow from 7.8 billion today to an estimated 10 billion, and global
foor area from new building stock is set to double by 2060, when
around 70% of energy will still be sourced from fossil fuels.
The buildings we have already built continue to use energy, and
in Europe alone some 75% of existing buildings are considered
energy inefcient, yet retrofting is taking place at a snail’s pace.
The buildings we haven’t yet built provide a once-in-a-lifetime
opportunity to make big, long-lasting impacts in the struggle
against climate change.
The book is about the energy we use to run our buildings – operational
energy (and thus operational carbon), which typically constitutes up
to 80% of the whole-life energy (WLE) and whole-life carbon (WLC)
of a building today. Reducing energy use remains the acknowledged
priority, but as we succeed in reducing operational energy, embodied
energy (from material processing, construction, maintenance and
demolition) will constitute a greater proportion of the WLE and WLC of
a building, and so will come under greater scrutiny.
Global CO emissions ebb and fow. While they levelled of in 2019,
2
mainly due to increases in renewable and nuclear energy, it is worth
noting that the growth in energy-related CO emissions in 2018 was
2
caused by unpredictable weather and the economic state of nations:
robust economies build more, unseasonably hot or cold weather
leads to occupant discomfort, energy is used to achieve comfort,
releasing CO. The principles of passive design in the rules of thumb
2
ofer a route to decarbonising those relationships, wherever you are
in the world. The rules then act as a platform from which to design
energy-positive and carbon-negative buildings which do not merely
minimise impacts, but which make a positive contribution to the
solutions we need.
PREFACE V
INTRODUCTION
Our ancestors knew how to create comfortable indoor conditions
with modest use of resources in their indigenous architecture,
and we must now relearn their intuitive skills and apply them for
tomorrow’s world. This book seeks to reintroduce to the reader that
intuitive knowledge, explaining what works in buildings that use litle
or no energy in their operation, wherever they happen to be on the
planet. It aims to provide the reader with three things:
ʢ an understanding of the universal rules of nature which govern
the way buildings respond to their environment
ʢ specifc low-energy-use, rule-of-thumb solutions for new
buildings or for retrofting existing buildings
ʢ guidance on where CO emissions can be minimised while
2
adopting the rules of thumb.
The rules of thumb are about the fundamentals of energy efciency.
For those who wish to proceed into measurement, calculation,
modelling and further research, a narrative bibliography provides
guidance on the key texts and some of the basic formulae which lie
behind the rules.
This second edition has a new intention, which is to align with the
widespread declaration in 2019 of a global environmental and
climate emergency. While the book is still about reducing energy
use through passive design, which is the acknowledged frst priority
when seting out to make net-zero operational carbon buildings, the
impacts buildings have on emissions and the relationships between
embodied and operational carbon are now embedded within the
rules. The bibliography now incorporates the construction industry’s
climate emergency response, with a life-raf of timely publications by
the Royal Institute of British Architects (RIBA), the American Institute
of Architects (AIA), the London Energy Transformation Initiative
(LETI), the Chartered Institution of Building Services Engineers
(CIBSE), the World Green Building Council (WGBC) and others, with
their guidance, targets and action plans, as we learn more about
what our buildings are really made of and how we could make,
operate and occupy them.
VI 101 RULES OF THUMB FOR LOW-ENERGY ARCHITECTURE
Buildings exist to modify the climate, from whatever the outside
conditions might be, to create a comfortable indoor environment.
For new buildings the process by which this is achieved is an
integrated one that starts with consideration of the siting and
location of a building, moves to deliberations on orientation and
form, and then on to the design of the building envelope (the walls,
roof and foor, also known as the building fabric in this book) and the
interior spaces. The fnal stage is one in which the occupants decide
whether their building has succeeded in creating a comfortable
environment, and if not they make themselves comfortable,
traditionally by using energy to supply heating or cooling. There is
a maxim which says ‘buildings do not use energy, people do’, so
the rules of thumb promote robust, intuitive architecture in which
occupants are encouraged and taught to have control over their own
internal environment.
The design process described above is refected in the organisation
of this book. It is worth noting that the early design decisions are
more permanent than the later ones: for example, unless the result
is a transportable architecture, the location and orientation of a
building will not change once the building is built, whereas the
building envelope can be upgraded with additional insulation, or
in response to new technologies that become available. The early
architectural considerations have a major bearing on the energy
efciency of a building. The decisions are crucial, and so had beter
be right: the rules of thumb are there to provide guidance on these
early, permanent moves which link our buildings with the natural
world and are also key ingredients of a poetic architecture.
Embodied energy (and thus carbon) is stored in the materials
used to make our buildings low-energy use, and there have been
adjustments to the rules of thumb to refect this relationship.
The inclusion of a cautionary rule of thumb about unintended
consequences should be of interest to those involved in low-carbon
retroft. Buildings are still about people, and there has been much
recent academic research in physiology, and investigations into
what constitutes (and how we measure) human comfort. Much of
it indicates a closer relationship than we thought between energy,
comfort, and health and wellbeing in our buildings: this theme is
INTRODUCTION VII
now highlighted within the rules of thumb. There is a new rule for
the way building size and form infuence energy use, and another,
inspired by author and teacher Baruch Givoni (1919–2019), considers
seasonally adaptable architecture, of which numerous vernacular
examples exist, the idea having lain largely dormant until recently.
Some rules, such as the previously mainly experimental Trombe wall,
might be considered outliers, but advances in energy modelling
have led to its appearance recently in both residential and public
buildings in varied climatic regions including South America and
northern Europe, so these rules remain steadfastly in place to inspire
low-carbon innovation.
For this edition, a new ‘see how’ device is incorporated within the
rules, making connections between those rules which are a call to
action and those that provide concrete, practical solutions to act
on. This edition still uses the notation CO for carbon dioxide,
2
but it also adopts the now-commonplace use of the term carbon
as a proxy for both operational and embodied CO. There is also
2
an author’s ‘Top ten reads’, which lists essential texts that have
infuenced the book and that it is hoped might provide inspiration
through further reading.
The book aims to be relevant globally, which presents a number of
challenges to author and reader. One difculty all design teachers
face is how to refer to where the sun is – a fundamental factor
infuencing many of the rules of thumb. When referring to the facade
of a building which is oriented towards the midday sun, the term
‘south-facing’ is fne in the northern hemisphere, but in the southern
hemisphere it traverses the sky in the north, so the facade facing
the sun is north-facing. I have opted mainly to use the awkward, but
functional, ‘solar-oriented’ or ‘south-facing (north in the southern
hemisphere)’ and, occasionally, ‘equator-facing’. The facade
opposite the sun is sometimes referred to, again rather clumsily, as
‘non-solar-oriented’.
The rules of thumb are applicable to today’s climate regions and
to future uncertainties. For example, some temperate regions have
begun to experience climates more like the hot-summer/cold-winter
climates discussed in the book, meaning that the rules which apply
VIII 101 RULES OF THUMB FOR LOW-ENERGY ARCHITECTURE
today in winter in cold regions and in summer in hot regions will
need to be considered. The rules show how our buildings can be
resilient and adaptable to an increasingly unpredictable climate.
Through their simplicity, they invite creativity in making buildings
which are in tune with the natural world while solving the great
environmental challenges of our age, forging a new symbiosis
between people, buildings and climate.
It remains to be seen what we do with the body of emergent
research into internal environments spawned by the coronavirus
pandemic, but buildings that work with, not against, the forces
of nature have always sought to be healthy buildings, and their
atributes seem also to be those that can help keep us safe in times
of invisible contagion.
The second edition has been infuenced by research in subjects in
the natural world as diverse as the non-visual efects of daylight
since the discovery of a new receptor in the human eye, to what we
might learn of the biomimetic potential of photoperiodic plants, and
the passive ventilation systems of the black-tailed prairie dog.
Afer applying the rules of thumb to minimise operational energy
use, it is the second book in this series, 101 Rules of Thumb for
Sustainable Buildings and Cities, which gives guidance on how to
use global resources sustainably, how to design for human health
and wellbeing, options for alternative and renewable energy sources,
and strategies for making buildings work in a net-positive way, in
concert with our planet’s ecosystems.
INTRODUCTION IX