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94 W
HITE
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TREET
, L
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N1 9PF
Tel: 020-7837-1228 ? fax: 020-7837-1141
e-mail: james@sustainweb.org
website: www.sustainweb.org
Edible Buildings
-benefits, challenges and limitations
James Petts.
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2
Not a new concept
In many parts of the world growing food on and around buildings is an economic necessity.
Herbs are grown on rooftops in Santiago, silkworms on balconies in Old Delhi, pigeons in
downtown Cairo, rabbits in Mexico City shanties and vegetables in Haiti
1
. Some city farmers
attach containers to their walls and grow melon and cucumber up them, whilst others keep
goats and cows on rooftops.
Sustainable strategies of particular relevance and significance to ‘edible’ architecture
[agritecture] include the maximum use of; vertical height, micro-climates and reflected
light, and water; conservation, de-contamination, and recycling, and the production of high
yielding, high turnover and high value crops.
2
Commercial enterprises are likely to
concentrate on a small number of crops whilst amateur gardeners a greater diversity.
Garden design strategies may follow permaculture and ecological principles to maximise
yields whilst benefiting people and the environment.
Sustainable techniques of importance in an urban context include organic; cultivation,
composting and biological pest control, spatial and temporal annidation
3
, intercropping,
companion planting, and ‘guilds’.
Appropriate food crops will depend on a large number of factors ranging from the macro
and microclimates to the time and income of participants. Potentially suitable species for
using in conjunction with walls and other structures in temperate climates include; cherries,
kiwi, apples, pears, peaches, hops, courgettes and squash, peas and beans, blackberry,
loganberry, red, black, and white currant, gooseberries and figs. Plants will benefit from the
stabilisation of temperature due to the thermal properties of masses. They are also likely to
benefit from the release of heat from buildings through walls and windows. Plants will be
less prone to frost damage and their growing seasons extended. Obviously, consideration
has to be given to preserving the structural integrity of buildings and maximum loads for
roofs (See Technical).
Unfortunately, the urban environment is not fully utilised in an efficient and sustainable
way. No reliable estimates are available as yet, but the area of flat roof space in towns and
cities in developed countries must run into tens of thousands of acres. Taken with the sides
of buildings, this represents an enormous, under-utilised resource. Urban areas could
produce significantly more food because of the amount of surface that is available and the
[biological] intensity of production
4
. The potential is further increased when we consider
how much can be grown indoors or with protection.
There are numerous benefits of ‘edible buildings’ but also many barriers and limitations to
their installation and operation, some of which we examine next.
1
UNDP, Urban Agriculture –Food, Jobs and Sustainable Cities, UNDP, 1996
2
B. Mollison, Permaculture Design Manual, Tagari Press, 1991
3
B. Mollison, Permaculture Design Manual, Tagari Press, 1991
4
B. Mollison, Permaculture for urban areas and urban rural links, Yankee Permaculture, 1981
Page 3
3
Benefits, challenges and limitations
Environmental
The environmental benefits of ‘edible buildings’ include; the production of locally grown
food [reduction in ‘food miles’], the benefits to biodiversity (See Use), the protection of
surfaces from the elements, increased thermal insulation of buildings, macro and micro
temperature regulation, and mitigation and adaptation of climate change
5
. They may also
include improved sound insulation and control of soil and growing mediums, and of
possible pollutants such as fertilisers and pesticides. If composting of plant and/or animal
wastes takes place, nutrients will be recycled locally and waste assimilated to provide soils
and mediums for, and organic fertilisation of, crops. Roof and vertical gardens can also
assist storm water management and improvement of air quality through filtration of
particles by plants.
Unfortunately, contamination of food via the air, water and soil can be a serious obstacle to
food growing in urban areas because of both real and perceived threats. Produce grown in
front gardens is thought to be particularly vulnerable to contamination by vehicle emissions
although a study by Birmingham University
6
found that this is largely superficial -easily
resolved by thorough washing and the removal of outer layers of foods. Research by
Cornell University in New York and the Russian State Committee on Standards suggests that
food grown on rooftops and terraces is significantly less contaminated than that grown in
sub-urban plots or bought at local markets
7
. Certain strategies and techniques such as the
choice of crops, use of raised beds and green pollution barriers, and increases in soil
alkalinity, are thought to assist contamination abatement and remediation
8
.
Social
‘Edible buildings’ can help improve the aesthetics of urban areas and increase participation
of the community. Residents living in Apple Tree Court in Salford, England started to green
their estate in 1988 and now have a productive garden with allotments, polytunnels and
composting. This has brought about a positive change in the community and they have
gained confidence to develop other initiatives.
Everyone lives in buildings and a majority in the North work in them. Those without a front
or back garden, or in close proximity to allotments or community garden, still have the
opportunity to garden and grow food where they live and work. Generally, less affluent
households are likely to have less surplus space in which to grow food. These inequalities
reflect those found in society in general. Deprived communities and households may partly
overcome this problem by utilising all available areas and surfaces in homes and on estates.
Tenure in and around buildings is generally more stable and secure compared with other
urban food growing locations
9
. Participants can therefore plan further into the future and
develop larger capital improvement projects.
5
S. Peck &C.Callaghan, Greenbacks from Green Roofs: Forging a new industry in Canada, Peck & Associates, 1999
6
personal communication with Clive Birch, Chairman of Birmingham District Allotments Council, April 2000.
7
UNDP, Urban Agriculture –Food, Jobs and Sustainable Cities, UNDP, 1996
8
T. Garnett, City Harvest –the feasibility of growing more food in London, Sustain: The alliance for better food and farming, 1999
9
UNDP, Urban Agriculture; Food, Jobs and Sustainable Cities, UNDP, 1996
Page 4
4
Food that is harvested from household gardens is also likely to be fresher when consumed,
as it travels direct from the garden to kitchen and/or to be processed. This increases the
likelihood of higher amounts of vitamins and beneficial enzymes being present when it is
consumed by householders and may help to improve diet and nutritional intake.
Security is a major concern of people, especially in deprived inner city neighbourhoods.
Front and communal gardens tend to be more prone to theft and vandalism compared with
private, back and roof gardens
10
. However, they are all likely to be less prone than distant
areas given that similar conditions apply.
Economic
There are many economic benefits of ‘edible buildings’ with a number related to aspects
already discussed (See Environmental). Non-commercial participants will benefit from a
fungible income through a reduction in purchases of food from markets. Cost savings may
occur through the increased insulation of buildings [reducing energy bills], protection of
surfaces [extending the life of walls and roofs, thereby reducing maintenance and
replacement costs], and reduced need for storm water infrastructure and management
11
Additionally, the proximity to home and work saves time and effort
12
and reduces
participants’ incidental costs incurred by travelling to and from sites further afield [shoe
leather costs]. Employment and training opportunities can be increased in the food
economy and in auxiliary industries such as plant nurseries, roofing manufacturers and
landscape architecture businesses. Improvements in air quality may lead to improvements
in the health of residents and productivity of workers resulting in cost savings accrued to
individuals, Government health departments and companies.
However, ‘edible buildings’ and especially roof gardens can have high initial costs especially
if the building’s structure needs to be modified. Costs of consultants, insurance,
maintenance and materials can be a barrier to their initiation and development
13
. Insurance
costs can be high due to a lack of historic information about terrace, roof and balcony
installations. Furthermore, most of the cost savings will accrue over a number of years and
are therefore likely to be heavily discounted.
Technical
Technical challenges to growing food in conjunction with buildings include the suitability of
the existing surfaces for plants, the possible impact of root penetration especially from trees
if membranes are damaged during installation, and the limitation of types of crop available
for use due to the soil systems employed.
Sites such as balconies, terraces and roof gardens need particular consideration of their
maximum loads. Maximum loads are calculated by summing the ‘live’ load including
people, snow, wind, etc, and the ‘dead’ load including the roof itself, roof membranes and
growing mediums when saturated. Professional help is advisable in such instances although
this is likely to increase the cost of installation.
10
UNDP, Urban Agriculture; Food, Jobs and Sustainable Cities, UNDP, 1996
11
S. Peck &C.Callaghan, Greenbacks from Green Roofs: Forging a new industry in Canada, Peck & Associates, 1999
12
UNDP, Urban Agriculture, Food, Jobs and Sustainable Cities, UNDP, 1996
13
S. Peck &C.Callaghan, Greenbacks from Green Roofs: Forging a new industry in Canada, Peck & Associates, 1999
Page 5
5
Small to medium sized trees can be grown in large containers. However, they need to be
weighted or securely attached to the building if they are vulnerable to strong winds. Both
containerised trees and windbreaks may add to the ‘dead’ or ‘live’ load of the building
respectively -advice should be sought if considered necessary.
Informational
The creation of ‘edible buildings’ can be hampered by a lack of awareness and information
by participants, policy makers, academics, professionals and other stakeholders. It can also
be hampered by misconceptions by the public at large. The view that climbing plants will
damage surfaces, or that the roots of plants will damage the foundations of can be correct
in certain instances (see paragraph note) although major problems are rare and can be
largely mitigated by following appropriate designs and strategies. Education and awareness
raising of these aspects are necessary to overcome misconceptions and shortages of
information.
[Damage to walls may be accelerated by climbing plants if they have already started to
decay. Foundations may be damaged by trees with vigorous roots, it is advisable to plant
trees with small rootstocks and/or with a root barrier in between. It is recommended that
climbers be planted at least 40cm away from any wall so that their roots do not affect the
foundations.
14
]
Regulatory
Building standards vary across borders and can be used to encourage the greening of
buildings and improve their ease of use for growing food. Regulations in some parts of
Germany have required new developments to install green design aspects and technologies.
Costs are likely to be minimised if the appropriate structures and systems are in place from
the beginning.
Planning regulations can benefit or be barriers to ‘edible buildings’. If poorly designed
developments are granted planning permission this can lead to difficulties in starting and
developing food growing. Alternatively, developments that are ecologically designed,
including the maximisation of areas for planting and creation of sheltered microclimates,
will aid sustainable food production. Planning permission is sometimes required for
structural work and for greenhouses and conservatories if they are over a certain size –this
can lead to delays and increases in cost.
Planning guidance can be a barrier to roof and ‘vertical’ gardens on buildings where they
would overlook other private gardens and residences. Planners have to consider people’s
privacy and can be reluctant to grant a change of use of the roof of buildings
15
. However,
most people establishing a roof or vertical garden would also value their privacy and they
are likely to use trellising and screens to provide this.
Health and safety regulations including those for fire are there to protect life and minimise
injuries. It is best for participants to seek advice on health and safety from statutory bodies.
In the UK, appropriate fire exits and a minimum 1.5 metre high fence or wall, around the
edge of roofs are required if the public have access. If modifications are required,
adherence to regulations will obviously increase the cost of installation.
14
J. Johnston and J.Newton, Building Green, London Ecology Unit, 1985
15
personal communication with Justin Bere, Architect
Page 6
6
Operational
The cost of plants and materials can be a barrier to the installation and development of
‘edible buildings’ as well as any structural adjustments (See Economic). Installation and
maintenance can be made more difficult if heavy loads need to be transported to higher
locations. If labour is limited for such tasks, hoists, lifts and winches can be employed.
Access to the outsides of buildings is occasionally required for repairs and painting. Plants
can be damaged in these processes by scaffolding, paint and people. Inappropriate
maintenance, as well as burrowing animals, may cause damage to the bases of sites.
The urban environment, including homes and workplaces, makes water more available for
harvesting and irrigation
16
. As well as piped water supplies, rain drainage systems can direct
water to storage tanks to be used for plant irrigation. Household wastewater can be
remediated with the use of reedbeds and similarly used in the garden.
On balconies and rooftop gardens wind speeds are greater than those on the ground. Crops
which tolerate such conditions are appropriate whilst others will require greater protection
from the negative effects of strong and desiccating winds
17
. Food plants also need
protection from the sun and heat particularly if grown in a greenhouse during summer
months. Plants generally require more frequent watering and fertilisation if grown in arid
conditions, containers or shallow beds.
The garden design and choice of plantings will depend on many factors including the aspect
and orientation, final size, personal taste, climates, disease resistance, etc. Gardening
techniques will be the same as general areas although certain aspects will have a greater
emphasis. A good proportion of food grown in urban areas will be grown in containers.
Crops are also likely to have similar allies and foes to others in more conventional
gardening locations although differences will occur due to the location and environment.
For example, carrots grown on balconies or rooftops may suffer less from carrot root fly
whilst brassicas may be more prone to damage by pigeons.
Animal keeping is also practised on and around buildings although less so in the North.
Poultry and livestock are kept for their fresh meat, milk, and eggs, -providing the
householders with some of their essentials. Animals require at least twice daily feeding and
watering as well as weekly, monthly and yearly tasks, which limits their potential especially
where participants have neither the time nor the inclination. Microlivestock are perhaps
more suitable especially if space and time are limited. Apiculture is considered to have
fewer limitations. Bees produce greater quantities of honey in urban areas
18
, require a space
of only 2m
2
per hive, and have minimal maintenance and low cost of equipment.
Aquaculture systems also have potential for ‘edible buildings’ although there is limited
information on this aspect.
The greatest potential regarding roofs and terraces obviously lies in accessible, intensive
roofs and terraces which can tolerate deeper soils and mediums. Lower weight systems such
as hybrid hydroponics and hydroponics can be employed if loads are restricted. Even
inaccessible, extensive roofs can be used for food production in an indirect way. Green
roofs with bee forage and other insect attracting plants would increase honey yields and
assist a balanced garden ecology.
16
UNDP, Urban Agriculture, Food, Jobs and Sustainable Cities, UNDP, 1996
17
M. Don, Life, The Observer Magazine, 5.12.99
18
Norman Carreck, Institute of Arable Crop Research, Rothmanstead, 1999
Page 7
7
Use
Much of the urban surface in courtyards, around buildings and estates is unutilised or
under-utilised. Competition for space with other economic or recreational activities can
occur although most sites are likely to be unused or have mixed usage. Spaces can be used
for activities such as commercial operations, energy generation (including photovoltaics),
household activities such as drying washing, and children’s play. However, gardening is
very popular and plants and gardens are generally seen as desirable not least in homes and
at work.
The use of artificial pesticides and other biocides in the garden will have negative effect
upon the organisms that live there and upon the wider environment, and could have
potential health risks to humans. Food growing activities, when they include ecological
principles and organic practices, increase the biodiversity of wildlife and plant varieties.
Ponds, animals, plants and soils will enhance the diversity and variation of both species and
habitats and may form parts of ‘green corridors’ or distinct islands within the city.
Conclusion
Growing food in cities and the built environment, whether as a livelihood or for enjoyment,
can contribute to food security and urban sustainability. The general ‘greening’ of urban
areas must be encouraged and implemented by practitioners and policy makers. The many
benefits associated with this, to the environment, to people’s health and well-being, as well
as providing the necessary conditions for food growing activities to thrive, should not be
ignored by professionals and laymen alike.
At the same time, however, we must recognise that if cities are to be sustainable, links must
be made with the urban fringe and surrounding rural areas. Built environments do offer
large surface areas for food production but how much is practically utilisable remains
debatable. Farms, allotments and imports provide the bulk of cities food and will for the
foreseeable future. Opportunities do exist for food production in association with buildings
and other structures but we must be aware of the difficulties and challenges that this unique
situation brings.
Page 8
8
Glossary
Agritecture
-‘the practice and study of food production using buildings and
other structures’
Annidation
-‘layering and timing of plants to utilise all available space and
time’
Apiculture
-‘beekeeping for honey and other products’
Aquaculture
-‘use of water resources for agricultural production’
Companion Planting
-‘planting crops together which have a symbiotic relationship’
Discounting
-‘reduction in the present value of income and costs because
accrual is in the future’
Food Miles
-‘the distance which food travels down the food chain, from
primary production to retail and consumption’
Fungible income
-‘income saved by substitution of purchased goods and services’
Guilds
-‘associations or groups of animals and plants which
have a symbiotic and synergistic relationship’
Intercropping
-‘production of more than one crop in the same space’
Microlivestock
‘small livestock including guinea pigs, rabbits and
poultry’
Organic agriculture
-‘agriculture that does not use artificial chemicals or
monocultural practices’. Its philosophy is to feed the soil to feed
the plants to feed the animals’
Permaculture
-‘ecological design for landscapes, buildings, gardens,
economies and communities’
Shoe Leather Costs
-‘incidental costs incurred by travelling’
Note:
Sustain: The alliance for better food and farming (formerly the National Food Alliance and the SAFE Alliance)
advocates food and agriculture policies and practices that enhance the health and welfare of people and
animals, improve the working and living environment, promote equity, and enrich society and culture. Sustain
represents over 100 national public interest organisations working at international, national, regional and
local level. James Petts is an economist and currently the project co-ordinator for City Harvest –Sustain’s
Urban Agriculture programme.
Disclaimer:
This paper is based on the author’s own experience and a review of research and projects concerning urban
food production in association with the built environment. It is not to be cited or referenced without the
author’s permission. It does not necessarily represent the views of Sustain or any of Sustain’s members.
Although it contains some useful insights into the subject, for more technical aspects, it is for the reader to
ensure that any necessary professional help is sought before any practical work is conducted. Sustain will be
conducting a more in depth study and disseminating the results during the course of its Edible Buildings’
project.