Oula Lehtinen – CC BY-SA 3.0

Approximately 5.7 million solid-walled houses exist in England, comprising 25% of the housing stock. Most were built between 1750 and 1914. Research shows that their energy efficiency has been underestimated for decades.

The English Housing Survey (EHS) defines solid-wall construction as a building where external load-bearing walls are made of brick, block, stone or flint with no cavity. In England, the shift to the use of solid-wall brick construction began during the great rebuilding from mid-16th century.

For the present English housing stock, the overwhelming fraction of solid-walled dwellings, constructed mostly of brick, derives from the expansion of population from the mid-18th century to the beginning of the First World War. Solid walls continued to be the most common construction for the domestic sector until the British housing boom of the 1920s and 1930s.

Wall Thickness

The most widely used estimate of the U-value (the measure of thermal conductivity) of a UK solid-wall property is 2.1 Wm−2 K−1. However, there is growing evidence that solid-wall U-values are much lower than previously assumed. Several studies in recent years have found that the mean or median U-values measured for solid-walled construction were around 1.3–1.4 Wm−2 K−1. There are two reasons for this large discrepancy.

First, standard solid brick wall U-values are based on an assumed wall thickness of 220 mm brick and approximately 12 mm of dense plaster. Modern bricks are 220 mm long and so this assumption would be logical for a modern brick wall. However, the thickness of 220 mm was used as a conservative estimate to capture variation in brick production. Following the Great Fire of London in 1666 brick properties over two stories were required to be constructed with walls that were more than one brick thick.

The required thickness of load-bearing masonry walls in England therefore increases with the height of the building. While two-storey buildings can be built with walls of just over 200 mm thickness, three-storey buildings require a minimum of 300 mm and four-storey buildings require walls of at least 400 mm. Consequently, it is obvious that the mean thickness of solid walls in the UK housing stock is likely to be greater than the nominal 220 mm of a single brick wall.

Air Cavities

Secondly, so-called ‘solid walls’ are in fact often not completely solid. Brick walls can be built up in a variety of different patterns, but are typically constructed with a mixture of brick types, with some going straight through the full depth of the wall, known as headers, and some laid side by side, known as stretchers (see image above). In order to allow walls to be constructed with a regular type of mortar bond, the total width of two adjacent stretchers is less than the length of a header by the width of a mortar joint, which is typically 5–10 mm.

Although some mortar will intrude into the space as snots from joints between stretchers, the practical constraints of bricklaying mean that this gap is often not filled with mortar. There is a high probability that solid-wall segments built with stretchers contain air gaps. If stretchers are assumed to comprise 50–80% of the wall surface, with air gaps of the order of ≈10 mm, then a straightforward calculation with identical assumptions regarding brick density etc. yields U-value estimates in the range of 1.65–1.8 W−1 m2 K.

‘Solid’ stone walls may also contain residual air cavities for similar reasons. Walls built with stone are often thicker overall than single-brick walls and often employ rubble-filled cores. It is almost certain that there are voids within these cores that would increase the thermal resistance of the element relative to that of a completely solid wall.

Consequences

Among the many implications for policy, discrepancy between real-world U-values and U-values assumed in energy modelling and standard UK building assessment protocols suggests that standard solid-wall U-values may be inappropriate for energy certification or for evaluating the investment economics of solid-wall insulation.

Reducing the represented U-value of solid walls in the stock from 2.1 to 1.3 Wm−2 K−1 reduces the estimated mean annual space heating demand by 16%, and causes approximately one-third of all solid-wall dwellings to change Energy Performance Certification (EPC) band.

Source:
Li, Francis GN, et al. “Solid-wall U-values: heat flux measurements compared with standard assumptions.” Building Research & Information 43.2 (2015): 238-252. http://www.tandfonline.com/doi/full/10.1080/09613218.2014.967977

Researchers have generally blamed the performance gap on careless work by builders, overly complicated energy-saving technology, or the bad behaviors of the eventual occupants of a building. But a new study puts much of the blame on inept energy modeling. The title of the study asks the provocative question “Are Modelers Literate?” Even more provocatively, a press release from the University of Bath likens the misleading claims about building energy performance to the Volkswagen emissions scandal, in which actual emissions from diesel engine cars were up to 40 times higher than “the performance promised by the car manufacturer.”

Read more: Why Don’t Green Buildings Live Up to Hype on Energy Efficiency?

A lamella roof, also known as the “Zollinger roof” (after Friedrich Zollinger), is a vaulted roof made up of simple, single prefabricated standard segments (mostly in timber) as a way to span large spaces. The individual pieces are joined together with bolts and/or plates to form a rhomboid pattern. Wooden sheathing covers the structure on the outside. The lamella roof was patented in 1910 and became popular between the World Wars, especially in Germany when metal for construction was in short supply. Some of these structures are now almost 100 years old and many of them remain in very good condition.

Read more: Lamella Roof, Open Source Ecology.

“The Salt Project is a biomimetic attempt to create architecture using seawater in the desert. By using locally available resources we can grow plants and create architecture without producing waste. The idea is to pump up seawater in arid areas around the world, split it in salt and fresh water, use the fresh water for produce and use the salt for architecture.”

“First we pump up the seawater with a pipe and pump installation powered by solar power. The seawater is pumped to Seawater Greenhouses where crops are grown. The remaining brine goes to salt pans to be turned into salt. Another part of the seawater goes to the algae farming area where starch is grown. The starch and salt form the building material.”

“After several tests at the TU Delft faculty of Civil Engineering it turns out that the material has around the same strength as other common vernacular building materials such as ice, rammed earth and simple masonry structures. Similar to the properties of these materials, the salt material deals well with compressive forces and not so much with tensile forces. This means a typical salt structure would be for example an arch, a dome or a shell structure.”

“A fantastic property of the salt is its translucency when it’s cast or 3D printed in thin panels. When shining a light on it silhouettes behind the material become visible, leading to very interesting architectural possibilities. The colour of the material is obviously very white, a feature very handy in desert environments as it will reflect the sunlight as much as possible.”

“Of course the weak point of salt is the fact that it dissolves in water. This is currently being handled by applying a coating to the material. Currently research is being done to bio based coatings that damage the environment as little as possible. Other strategies for waterproofing the material could be building a transparent tent structure over it or covering it with things like reed or sand.”

See & read more: The Salt Project. Via VIBA.

Malawi home built with rammed earth and thatch roof in Chizogwe village. Picture: Jon (Twingi) Sojkowski

I am a registered architect and I have a passion for African vernacular architecture. I recently (Sept. 2014) traveled to Malawi to document the vernacular architecture in the entire country. 4,700 pictures are on the web page.http://www.malawiarchitecture.com/

I also wanted to share with you my latest project… a data base on African vernacular architecture. This project was started because of the lack of information available on line. The data base includes images from every African country. Here is the link to the site:

http://www.africavernaculararchitecture.com/

The goal of the project is to have people, who live or work in an Africa country, submit pictures of vernacular structures to the data base to share with the world. Full credit is given for every picture submitted. For too long, African vernacular architecture has been a topic that has been both under-documented and, unfortunately, ignored. People say there needs to be documentation but yet nothing is done. Whether this is due to difficulties in obtaining funding or just apathy, the fact remains that very little data can be found online.

House with porch in Malawi. Picture: Jon (Twingi) Sojkowski

Architecture is as much of a part of a countries culture as is language, music or art. African vernacular architecture is disappearing. I witnessed that fact in Malawi. There are many reasons why vernacular materials and construction techniques are being abandoned in favor of western ones. One main reason is the lack of documentation, especially finding information on line.

I am hoping you could share the project with your readers, the more awareness, the better the chance to convince people to submit pictures to the data base. There is no other resource for African vernacular architecture like the data base: there is no organization gathering information, there is no active research, there is no voice for it. I will gladly answer any questions that you might have about the project.

Cheers,

Jon (Twingi) Sojkowski

“How do we go about designing buildings today for tomorrow’s weather? As the world warms and extreme weather becomes more common, sustainable architecture is likely to mean one major casualty: glass. For decades glass has been everywhere, even in so-called “modern” or “sustainable” architecture such as London’s Gherkin. However in energy terms glass is extremely inefficient – it does little but leak heat on cold winter nights and turn buildings into greenhouses on summer days.”

“For example, the U-value (a measure of how much heat is lost through a given thickness) of triple glazing is around 1.0. However a simple cavity brick wall with a little bit of insulation in it is 0.35 – that is, three times lower – whereas well-insulated wall will have a U-value of just 0.1. So each metre square of glass, even if it is triple glazed, loses ten times as much heat as a wall. Cutting back on glass would be an easy win. Windows need to be sized, not glorified, and sized for a purpose: the view, or to provide natural light or air. Windows also need to be shaded. Many would argue that we need to re-invent the window, or the building. We need to build buildings with windows, rather than buildings that are one big window.”

Read more: Climate change means we can’t keep living (and working) in glass houses. Via Lloyd Alter.

“The simplest homes in town were built using cratchets — natural forks in trees — as support for the ridgepole of the roof. The walls are built up with “wattle” — small sticks for the lattice structure — and “daub” — a mortar of clay, earth and grasses. Instead of using the traditional English lime wash to protect the walls, the colonists took advantage of the plentiful wood in the America and created clapboard siding by cleaving wood into thin boards. For the thatch roofs, large bundles of water reed or wheat straw are woven with a giant needle by two people working in tandem (one outside and one inside). “It’s like a giant quilt made of grass,” explains Brault, “which makes a water-tight roof that essentially acts as a giant sponge. It absorbs water and laps it off.”

Watch the video. Picture: a wattle and daub wall in Germany.

Almost a quarter of a million windmills worldwide will need to be replaced by 2030. The rotor blades are made of valuable composite materials that are difficult to recover at the end of their energy generating life. New generation rotor blades made of glass or carbon fibre composite material have average lifespans of between 10 and 25 years. Recycling of glass fibre composite is possible though complex. Recycling of the more highly valued carbon fibre composite is currently impossible. In many EU countries landfill of carbon composites is now prohibited. Thus, many rotor blades at the end of their wind turbine life are currently shredded and incinerated. At current growth rates, by 2034, there will be about 225,000 tonnes of rotor blade composite material produced annually, worldwide.

The Dutch firm Superuse Studios has found a solution to the growing mountains of waste generated by the wind industry: making use of end-of-life rotor blades in design and architecture. The realised projects demonstrate the technical applications and potential for blade made designs and architecture. In their second life as design and architectural elements, rotor blades could be used for a further 50-100 years, or more. Blade made designs are durable, iconic, compete economically, and reduce the ecological footprint of projects in which they are used.

REwind Willemsplein

Public seating made from rotor blades was designed and installed for the Rotterdam municipality. The REwind public seating is located at Willemsplein, a public square at the foot of the well-known Erasmus bridge. The municipality was in need of durable, indestructible seating with iconic quality for people waiting to board harbour tour boats, but which could also be temporarily removed, when necessary, to make room for public events. Nine rotor blades from Friesland destined for incineration were used.

Public seating in Rotterdam. Picture by Denis Guzzo. More pictures.

Five blades were used for seating, three as backrests, and one as place marker. By adjusting the angles and positions of the blades ergonomic public seating with a diversity of seating options was created. Seating depths vary from 30 to 80 cm, providing upright seating to more relaxed lounging options. The 6 metre long blades are attached with bolts to 1m3 concrete aggregate blocks made heavy enough to keep the lightweight blades in place. The aggregate is 100% recycled concrete rubble from Rotterdam.

Wikado Playground

The first Wikado built at the Meidoorn playground at Oude Noorden, Rotterdam, was built for the same budget as a comparable standard playground, and has an ecological footprint fifty times smaller. The playground was designed to maximise imaginative play, social interaction, and children driven game development. The inherent properties of rotor blades make this material an excellent choice: weather and wind resistant, organic, ergonomic shapes, and a strong and rigid structure. The cylindrical portion of 30 m long blades has a diameter of 1.4 m and makes for interior play spaces. One of the five 30 m blades was used intact. The remaining four blades were cut into three sections.

Playground in Rotterdam. Picture by Denis Guzzo. More pictures.

The four cylindrical end sections were transformed into play towers that stand around the central play zone. Each tower has a distinct and recognizable character. The ‘towerflat’ has three rooms with peeking holes, the ‘watchtower’ with a former F16 cockpit on top, the ‘water tower’ with hand pump for children to pump water for mixing with sand, and the ‘slide tower’ to which the original slippery sides from the site are attached.

REwind Almere

Construction is underway of the Superuse Studios’ designed shelters for the thousands of daily commuters to use the bus-train transfer station at Almere Poort. The durable and indestructible shelter design uses four 30m rotor blades. Waste rotor blades are easy to find in Almere, Holland’s #1 wind-energy region. Stacked in a Stonehenge like manner two 30 m blades are used to create a large shelter. Two of these large shelters are being built. The changing shape over the length of the blades gives a shelter roof that morphs into different shapes depending on the angle from which is it is viewed.

A bus shelter made from rotor blades. Source: Blade Made, Superuse Studios.

Every part of the blade is used. The blades were cut in four sections to harness the different inherent qualities along the length of the blade. This gives construction pieces that are essentitally readymade for different construction purposes. The strongest and heaviest part (former connection to the wind turbine axial) is used as roof supporting columns, and the widest part of the blade for the roof. The tip of the blade is used for the long seating bench, and the circular end pieces are used for large planting pots placed around the site. Completion is expected by the end of March 2014.

Future Plans

Superuse Studios has been invited to partner with the Danish ‘Genvind Consortium‘,  a consortium of over 20 organisations, including Vestas, the biggest wind turbine producer of the world. The main goal of this consortium is to find solutions to the growing mountains of waste generated by the wind industry. Superuse Studios have joined the Genvind project to demonstrate how worldwide blade made projects that reuse wind rotor blades can play an important role in the processing of this composite material. The collaboration already resulted in very concrete plans for a blade made bridge in Denmark.

Thanks to Tim Joye.

Building on statistical analysis of the built fabric of three major American cities [San Francisco, Seattle, and Washington, D.C.], the research demonstrates that established neighborhoods with a mix of older, smaller buildings perform better than districts with larger, newer structures when tested against a range of economic, social, and environmental outcome measures.”

“Older, Smaller, Better. Measuring how the character of buildings and blocks influences urban vitality“, National Trust for Historic Preservation, May 2014. Via Lloyd Alter.

Families living in traditional courtyard houses of Baghdad, without mechanical ventilation or heating, migrate by day and season for comfort. In September or October, they move around the courtyard to rooms facing south. In April or May they shift to the north-facing rooms. In summer there is a daily vertical migration, the afternoon siesta being spent at the lowest levels and the nighttime sleep traditionally being taken on the roof under the stars.

Picture: muhammadshnait91.tumblr.com

Such migrations mean that space is used with a freedom unusual in modern life and in the West. Recent correspondence from Mounjia Abdeltif-Benchaabane, a professor of architecture in Algiers, describes how rooms there have not traditionally been organized with regard to individual use or established purpose:

A living room becomes a sleeping room at night. Closets are full of mobile furnishings. In the morning everything is hung near windows to air out under the sun before being reused, perhaps in a different room. The kitchen is a multifunctional space. They cook on the floor even if they have modern tools.

A long-established Arab concern with privacy, in conjunction with the custom of migrating through the house, established the texture of some old cities like Baghdad. Since the roof is used for sleeping during nearly half of the year and the privacy of the family at night is fundamental, no house could look down upon its neighbor nor could one house look into the courtyard of another. The result was an effective building height control with advantages for solar access: no house could overshadow another, thus assuring wintertime light and heat to upper living spaces.

Quoted from “Ritual House: Drawing on Nature’s Rhythms for Architecture and Urban Design“, Ralph L. Knowles, 2006.

“In the south of Burkina Faso, a landlocked country in west Africa, near the border with Ghana lies a small, circular village of about 1.2 hectares, called Tiébélé. This is home of the Kassena people, one of the oldest ethnic groups that had settled in the territory of Burkina Faso in the 15th century. Tiébélé is known for their amazing traditional Gourounsi architecture and elaborately decorated walls of their homes.”

“Burkina Faso is a poor country, even by West African standards, and possibly the poorest in the world. But they are culturally rich, and decorating the walls of their buildings is an important part of their cultural legacy in this area of the country. Wall decorating is always a community project done by the women and it’s a very ancient practice that dates from the sixteenth century AD.”

Read more: Decorated Mud Houses of Tiébélé, Burkina Faso. Picture (and many more pictures): Rita Willaert.

Build-It-Solar blog writes:

Kotaro Nishiki built a passively cooled home in Leyte Philippines at 11 degs north latitude that incorporates a number of unique cooling features that allow the home to be cooled passively and without electricity…

In this area, most homes are constructed of concrete, and the concrete structures tend to absorb solar heat during the daytime, and then retain that heat through the night making the homes uncomfortable.

Kotaro’s design is centered on eliminating these daytime solar gains. He keeps the whole house shaded using these techniques:

• The south facing single slope roof has on overhang on the south that keeps the south wall in shade most of the day.
• The north side of the house is shaded by an roof extension sloped down to the north that shades the north side of the house most of the day.
• The roof is double layered with airflow between the well spaced layers.  This greatly reduces solar heat gain through the roof.
• The east and west walls of the house are double wall construction with a couple feet between the walls.  The shading that the outer wall offers plus airflow between the double walls keep the wall temperatures low.
• In addition, he has worked out ways to take advantage of the night
  temperature drop and to use thermal mass on the basement to provide some
  cooling.

More: A unique, passively cooled home in the Tropics (Build-It-Solar), Passive Solar House in Tropical Areas (Kotaro Nishiki). Build-It-Solar has more examples of passively cooled houses.

“The team enlisted Vandkunsten to design a new house that combines the traditional material with twenty-first century construction techniques. Seaweed is at the same time very old and very ‘just-in-time’, because it is in many ways the ultimate sustainable material, Realdania Byg’s Jørgen Søndermark told Dezeen. It reproduces itself every year in the sea, it comes ashore without any effort from humans, and it is dried on nearby fields by sun and wind. It insulates just as well as mineral insulation, it is non-toxic and fireproof, and it has an expected life of more than 150 years.”

See and read more at Dezeen. Via Lloyd Alter.

Included are instructions for dozens of worry-free shelters for you to chose from, including a sod house for the lawn, a treetop house, over-water camps, a bog ken, and much more. Satisfying the builder’s need for the creature comforts of home, it also provides tips on how to build hearths and chimneys, notched log ladders, and even how to rig a front door with a secret lock. Illustrated throughout with a bounty of helpful line drawings, Shelters, Shacks, and Shanties harkens back to the can-do spirit of the American frontier that still thrives today.”

Shelters, Shacks, and Shanties; and how to build them“, D.C. Beard, 1914 (Gutenberg free e-book). The description is from the 2008 edition (Amazon). Thanks to Thurston.

“The Nubian Vault technique is an age-old method of timberless vault construction, originating in upper Egypt. It uses only earth bricks and earth mortar. Nubian vaults built over 3,000 years ago at the Ramesseum mortuary temple, Luxor, are still standing. During the last ten years, Association La Voûte Nubienne (AVN) has successfully introduced a simplified, standardised version of this ancient technique in Burkina Faso, Mali, Senegal, and Zambia. This standardised technique is:

• Ecologically sustainable – no corrugated iron roofing sheets, nor timber beams, rafters, or supports;
• Carbon neutral – none of the construction materials are manufactured, or transported long distances, nor do any trees need to be cut down;
• Economically viable – only locally available raw materials (earth, rocks, and water) are used, favouring local economic circuits and self-sufficiency;
• Comfortable – due to the excellent thermal and acoustic insulation properties of earth construction;
• Durable – NV buildings have a far longer lifetime than those with corrugated iron and timber roofs, and maintenance is simple;
• Modular – applicable to a wide range of buildings (houses, schools, healthcentres…), of different styles (flat terrace roofs, two-storey buildings, courtyard buildings…), which are easily extendable;
• Vernacular – incorporating tradtional practices and aesthetics of earth architecture.

The major cost element in using the Nubian Vault method is labour, often provided by family members and neighbours on an exchange / barter / self-build basis, thus keeping cash in the local economy; the raw materials (earth, rocks, water) are locally available and ecologically sound; construction with mud bricks and mortar is traditional in the Sahel region – the innovation of vault construction can easily be incorporated into existing practice.”

More information, including building guidelines and house plans, at “La Voûte Nubienne” (website in English and French).

Previously:

• Tiles as a substitute for steel: the art of the timbrel vault
• The Sustainable Urban Dwelling Unit (SUDU)
• Timbrel vaulting in South-Africa by Peter Rich Architects
• Timbrel vaulting using cardboard formwork

The architects consider their work to be a toolbox, a starting point for thinking outside the conventional norms and recepies. They argue that decentralized services are more flexible, provide more autonomy, and are more efficient in space, energy and materials.

Antoni and Blasco present, in their own words, an equivalent to Neufert’s “Architect’s data“, the book for architects that records standardized dimensions for centralized systems. “Micromachins” is written in French but the visuals dominate.

“Micromachins”, Damien Antoni and Lydia Blasco, 2011 [download the page to get the high resolution PDF-document]. Thanks to Yann Philippe Tastevin. Update: the architects have added a new link with colour pictures and English translation.

Read more: Ancient ‘air-conditioning’ cools building sustainably.

The cooler cabinets were designed to hold fruits, vegetables, and other staples that needed to be kept cool but didn’t need to take up critical space in the era’s tiny ice boxes. The coolers were open to the basement to draw in cool air, which then wafted up and out a chimney or a wall vent.

When the refrigerator came along, it seems that, over time, the vents were boarded up and the California Cooler was all but forgotten. Today, if you walk the streets of my hometown, Berkeley, where most of the houses were built in the 1920’s, you will see many homes, and even apartment buildings, with the exterior vestiges of these vents.”

Read more: Resurrecting the California Cooler. Thank you, Adriana. Previously: Saving food from the fridge.

The ‘Sustainable Urban Dwelling Unit’ (SUDU) in Ethiopia demonstrates that it is possible to construct multi-story buildings using only soil and stone. By combining timbrel vaults and compressed earth blocks, there is no need for steel, reinforced concrete or even wood to support floors, ceilings and roofs. The SUDU could be a game-changer for African cities, where population grows fast and building materials are scarce.

In “Tiles as a substitute for steel“, we highlighted the medieval art of the medieval timbrel vault, which allowed for structures that today no architect would dare to build without steel reinforcements. The technique is cheap, fast, ecological and durable. Shortly after the article was published in 2008, the timbrel vault made a comeback with two rather spectacular buildings: Richard Hawkes’ Crossway Passive House in England, and Peter Rich’s Mapungubwe Interpretation Centre in South Africa.

The cardboard formwork technique described last week promises to bring even more dramatic architecture, but at least as interesting is the news that the catalan vault is now also applied to a much more modest form of housing: the Sustainable Urban Dwelling Unit (SUDU), a low-cost family dwelling built in Ethiopia.

The Sustainable Urban Dwelling Unit (SUDU).

Though less spectacular at first sight, it could form the proof that even megacities can be constructed without the use of steel, concrete or wood. The double-story building, which was completed in last summer, is entirely made from soil and presents an economical and ecological solution to many of Africa’s most urgent problems. The SUDU stands in Addis Ababa, Ethiopia, a country with a population of more than 80 million (growing at an average 7 percent per year). The building is a joint project of the Swiss Federal Institute of Technology (ETH Zurich) and the Ethiopian Institute of Architecture, Building Construction and City Development (EiABC).

The SUDU combines past technologies from different continents, resulting in a new approach to low-tech construction adapted to specific local conditions. In the Mediterranean region, where the timbrel vault originated, the tiles have traditionally been made from fired clay. In the SUDU, the construction technique is united with the African tradition of cement-stabilized, soil-pressed bricks, which use locally available soil. This technique is called compressed earth block (CEB) construction. The SUDU has been built largely following the same techniques used for the Mapungubwe Centre in South Africa.

Urban housing

The SUDU was designed to achieve both environmental and economic sustainability. Because Ethiopia has few material and financial resources, the design is aimed at eliminating the reliance on imported, expensive and energy-intensive building materials such as steel and concrete. More unusual is that the building also excludes the use of wood, for the simple reason that wood is equally scarce in the country. The entire structure is made from locally available construction materials – and in the case of Ethiopia, these are very few: soil and stone.

The Sustainable Urban Dwelling Unit (SUDU).

One of the most challenging present problems for Africa (and throughout the developing world) is the tremendous deficit in housing for the urban poor. In Ethiopia, this is reflected in the ubiquitous informal housing, comprising perhaps 80% of the built environment of its capital, Addis Ababa. The most common vernacular construction method – construction with Eucalyptus wood and mud – is an economically and environmentally sustainable method of construction, but the problem of such constructions is that they are limited to one story – putting a huge strain on available land.

Thus, this vernacular technology has been more recently replaced by large urban housing projects of reinforced concrete, heavily subsidized by the government. These massive edifices of concrete and steel neither offer a model for frugal, environmentally or economically sustainable construction, nor do they offer a low-cost alternative to housing because they are too expensive to construct. The result is that more and more people are forced to be living on the streets. Whether it is the United States or Ethiopia, governments seem to prefer homeless people over shanty-towns.

The Sustainable Urban Dwelling Unit (SUDU).

In poorer areas of Addis Ababa, dwellings are often constructed from corrugated metal. These dwellings cannot be expanded upon for multi-story construction, yet sprawl outward, consuming limited resources including wood, expensive imported materials, and land.

Urban density

The SUDU is an exploration of a “medium ground” between single story informal dwelling and massive scale urban density, as studies have shown that even two-story buildings dramatically impact urban density. As the example of Tokyo shows, a megacity can be largely based on double-story buildings. Because the other aim is to build using only locally available materials, and wood reserves are scarce, the goals of SUDU were to build two stories in soil – a significant challenge without the aid of steel, concrete or milled lumber. Multiple-story soil architecture has a long tradition in Africa, though none of it has been constructed without wooden beams.

Building multiple stories in soil is a significant challenge without the aid of steel, concrete or lumber

As soil and stone have limited tensile capacity, building with these materials demands compression-only structural solutions. For walls carrying dominantly vertical loads, this criterium is easily satisfied. However, once a space must be spanned, beam elements – which work in bending – are typically required. A beam, as a structural system, demands that its section can accomodate tension and compression forces, which is not possible when building in stone or soil only.

The Sustainable Urban Dwelling Unit (SUDU) under construction.

By adapting local soil knowledge to the production of soil stablized tiles, however, it is possible to introduce the technology of timbrel vaulting to allow floor and roof systems of pure compression in multiple story buildings. Ethiopia has a rich soil, which contains high levels of clay particles. Almost all excavated material in the city of Addis Ababa is a possible source for the material needed to build new structures. The SUDU uses rammed earth techniques to construct the first level of the building, with a 60 cm wide wall structure. The ceilings and floors and the building are done using a tiled vauling technique using sun-dried tiles (first floor) and loam (for the roof) made from the very same soil.

Contrary to most other vaulting techniques, the catalan vault does require little to no formwork, again bypassing the need for wood.

Model for low-cost housing

Apart from the ecological and financial benefits, the construction technique used in the SUDU offers additional advantages. By drawing upon traditional methods, it engenders pride and social cohesion within the local community. And by using only locally available materials, it provides local jobs, introduces new skills and stimulates self-sufficiency. Through the economic benefits, the SUDU may become a model low-cost housing unit for the urban poor in Africa. It is meant to be a showcase to convince decision makers, economists, urban planners and architects to rethink traditional building methods and find new ways to build a town or even a city.

The construction of the SUDU was led by Lara Davis, who published a blog where the building process is documented from A to Z. There is also a movie. The BLOCK Research Group of the Swiss Federal Institute of Technology (ETH Zurich) has a webpage that links to all the research papers on the construction method. A book was presented November 25. Also of interest is a special architectural 2010 issue of the ADTF Journal published by the African Technology Development Forum. Several articles deal specifically with timbrel vaulting building methods, and outline some of the remaining challenges:

• “Tile vaulted systems for low-cost construction in Africa“.
• “Design and Construction of the Mapungubwe National Park Interpretive Centre, South Africa“.

Previously:

• Tiles as a substitute for steel: the art of the timbrel vault
• Timbrel vaulting in South Africa by Peter Rich
• Timbrel vaulting using cardboard formwork
• Engineering for the ecological age: lessons from history
• Building with mud and steel frames
• Building with pumice
• How to build a reciprocal roof frame
• How to build an earthbag dome
• How to build a medieval city
• Birch bark sauna
• Innovation and tradition: the complete works of Hassan Fathy online
• Why older buildings are more sustainable
• The solar envelope: how to heat and cool cities without fossil fuels