Hebridean blackhouse vs volume housebuilder home – energy profiles compared

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The blackhouse, by contrast, was built with very low embodied energy, of which close to 100 per cent was renewable muscle power. The only significant heat-energy inputs were for the few iron components of the building. A 5kg wrought-iron pot chain and hook for a blackhouse would have cost, in the pre-modern period, around 200kg of renewable wood for charcoal-based smelting and forging. If zero carbon housing was possible to achieve with the simple technologies and constrained resources of the pre-modern Hebrides, it’s certainly possible today.

Circularity

From Donald Trump’s executive order on public buildings to the UK’s ‘Living With Beauty’ report, national architectural debate in Britain and the USA is wearisomely prone to restage 1980s battles between lovers of Modernism and those who want new buildings to pay cumbersome tribute to Classical architecture. In the face of the climate emergency, it’s time to say ‘a plague on both your houses’ – and, for that matter, on Victorian and Georgian architecture, too.

Source:Alamy

With today’s emphasis on energy efficiency and staggeringly advanced materials science, new British houses could be much more energy-efficient than the blackhouse. This is rarely the case. Operational energy in the Winstone, according to a 2013 study, is about 35 per cent lower than the average detached UK home, but the building still emits 2.86 tonnes of CO₂e a year – as much as an average new petrol car driving 24,000km. A blackhouse, in comparison, consumes 30-50 per cent less energy in the form of 1.4-2.1 tonnes of peat per year.

The blackhouse was probably less warmly heated. It is also smaller, but would have housed a comparable or perhaps larger family, so, in terms of domestic heat energy per person, the blackhouse’s simple masonry and thatch performed around twice as well as its technologically advanced modern counterpart.

Source:Iddon/Firth

On the almost treeless Outer Hebrides, even wood was restricted to the most essential building elements, such as trusses, doorframes and doors. Iron, one of the most energy-intensive materials of the pre-modern age, was used only where its technical properties were irreplaceable, for example for the slabhraidh, the chain and pot-hook that hung over the hearth. To save on metal, rafters and tie beams were joined with wooden pegs rather than nails, and even the door pivoted on wooden hinges.

When the whole or parts of contemporary buildings come to the end of their life, they are typically hard to dismantle and re-use, some parts going for energy-hungry recycling, others being ground up by powerful machines for use as low-value bulk material, and some going to landfill. A blackhouse shows circular economy to perfection.

Key sources for this article: Bruce Walker, ‘The Lewis Blackhouse: Green House of the Future?’ (1996). FLW Thomas, ‘On the Primitive Dwellings and Hypogea of the Outer Hebrides’ Proceedings of the Society of Antiquaries of Scotland 7 (1866-68); Alexander Fenton, The Island Blackhouse (1978); Bruce Walker and Christopher McGregor, The Hebridean Blackhouse (1996); Christopher Iddon and Steven Firth, Embodied and operational energy for new-build housing: A case study of construction methods in the UK, Energy and Buildings 67 (December 2013). Vaclav Smil, Energy and Civilization: A History (2017).

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In Britain, the age of unsustainable, carbon-intense construction began in the 17th century. Rebuilding London after the 1666 Great Fire produced about 300,000 tonnes of CO₂ from coal burned to bake its half-billion bricks and to calcine the lime for their mortar.

The circa 20m2 central space around the hearth of a blackhouse was both kitchen and living room

Florian Urban is head of History of Architecture and Urban Studies at the Glasgow School of Art.

Modern volume housing insulation systems, with their tendency to serious failures and a polluting, carbon-intense start and end of life, compare poorly with building smaller dwellings in sustainable local materials such as straw, thatch and turf. Relying on good insulation and body warmth with minimal additional energy input has to be a necessary goal for future construction.

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Modernity compares badly on transport carbon, too. Blackhouse residents walked short distances to work and worship, while most volume-built housing estates are remorselessly car-dependent, their whimsical road layouts and exurban sites militating strongly against walking and cycling. Each house has its protected parking to maximise the thoughtless ease of driving, helping its occupants to uphold the UK annual average of almost 13,000km per car.

Embodied energy

The roof beam was slanted so that animals’ body heat could rise from the byre into the living space. A hearth in the middle of the kitchen-living room floor radiated heat to residents, its warm, smoky air hanging under the chimneyless roof. Smoke’s slow filtration through the thatch preserved the perishable reed and straw from insects and repelled the countless midges. The chimneyless interior is much nicer than it might sound; peat smoke produces a pleasant smell, rather than the choking fug of wood or coal. As a 1960s visitor put it, ‘the blackhouse is definitely the cosiest you can find’.

If operational energy is higher in contemporary volume housing, today’s embodied energy is in another league. The Winstone’s cavity walls are made of aerated concrete blocks with a fired brick outer skin. It is roofed in fired tile and sits on sturdy concrete foundations.

The elegant Georgian brick façades and generous glazed sash windows so beloved of ‘traditionalists’ were, from a carbon point of view, as inherently unsustainable as the notoriously wasteful steel-and-glass boxes of the mid-20th century or the suburban homes of the present – part of the same architectural tradition as Cumbernauld and Brasilia.

Building range

The term blackhouse – taigh dubh in Gaelic—appeared in the mid-19th century, to distinguish the soot-filled fieldstone houses from the white, modern taigh geal (white house) that became popular on the Outer Hebrides in the 1850s. The brightness of the white house was bought at a substantial energy cost. It depended not only on high-embodied-energy render, but also on a chimney. Chimneys removed the fire’s smoke, but also 90 per cent of its heat.

Architectural principles supported the main goal of saving hard-won energy. Nearly all construction materials were local, and used as found, rather than heat-treated like most modern materials. Without cheap fossil fuels, bricks or tiles, structural steel or cement were too expensive for humble homes. The house was built from fieldstones found around the site and thatched with reed or straw. Double-thickness walls increased insulation. Openings in the wall were unglazed in older buildings – the intense heat energy required for making and shaping glass was unrealisable.

Car travel in the UK could be radically cut by planning for density and proximity of working and living – a basic principle of pre-fossil fuel life. Perhaps the starkest lesson that the pre-modern blackhouse has to offer is that the level of energy and carbon we spend on our building materials is, by world historical standards, deranged. Steel, glass and concrete all existed when blackhouses were being built, but they were rejected for their exorbitant cost in heat energy.

How does the blackhouse compare with today’s volume housing? Today’s buildings are, of course, far more sophisticated. Typical new blocks of flats in the UK now involve proprietary systems of structure, insulation, servicing and cladding requiring expert installation and maintenance. But when they fail, these can be hard or impossible to replace. Blackhouses, by contrast, were constructed and repaired using a limited range of knowledge and materials that allowed them to be built and kept up by the community.

The building costs approximately 50 tonnes of embodied carbon to build and to maintain over a 60-year lifespan (including necessary replacements of windows and wallboards). Most of this carbon footprint arises from burning fossil fuels for energy to make, transport and erect the materials. The largest emissions derive from concrete walls and foundations, both through high embodied fossil fuel energy and through the chemical reaction that makes cement.

Over 20 per cent of modern UK domestic energy consumption is for things other than heat; without the barrage of gadgets that characterise the contemporary interior, the blackhouse had no comparable energy consumers.

The traditional blackhouse typology isn’t a model for new housing in the UK. There would be little appetite for sharing a bathroomless, one-bedroom house with children and cattle, and current population densities would exhaust surviving peat supplies very quickly indeed. Peat regenerates slowly, and peat burning is partially banned in the UK and Ireland. The extreme localism of pre-fossil fuel rural life is not about to return, and the mobility of goods and people in our current era has many positive outcomes, despite its currently high carbon cost.

Evolved for a low-energy society, blackhouses maximised the comfort of their residents within the tight confines of their energy resources. Inhabitants typically lived a subsistence lifestyle reliant on small grain fields, cattle husbandry and a little fishing. Domestic comfort was basic by modern standards but satisfied the fundamental human needs.

To find architectural traditions with real relevance to construction in a climate emergency, we need to look back to the typologies and materials favoured in each region before fossil fuels took hold there. In the Hebrides, remote from the coal-fuelled industrialisation of the mainland’s cities, domestic dependence on coal came late. The last blackhouses, once common across the Highlands and Islands of Scotland, remained in use until around 1970, only two decades before architectural historian Bruce Walker celebrated them as possible ‘green houses of the future’. Domestic life in these buildings is memorialised in the Arnol Blackhouse on the Isle of Lewis, built 1852-95 following an old typology. Inhabited until 1966, it is now a museum managed by Historic Environment Scotland.

In addition, we must push governments, national and local, of any party, to enact and uphold powerful legislation and tax regimes to encourage retrofit, to monitor and restrict embodied carbon, to enshrine reparability and re-use, and to enforce limits on operational energy measured by post-occupancy testing, rather than by optimistic pre-construction modelling.

However, some of the principles of the blackhouse are hugely inspiring as we seek to move to a zero-carbon built environment. Low or zero-carbon materials such as timber and stone could be sourced locally across the UK to replace carbon-intense cement and steel.

The ‘Winstone’ costs about 50 tonnes of embodied carbon to build and to maintain over a 60-year lifespan

The hint of a sneer in the comparatively recent name blackhouse – contrasting it with newer ‘white houses’ kept clean by absurdly profligate chimneys – hints at a fundamental change of thinking and feeling required in our appreciation of architecture. New, shiny, white, pristine – these are the luxuries of an age rich in apparently consequence-free fossil-fuel energy.

Like many buildings of today, it was not meant to last, as the inhabitants usually did not own the land they worked and were frequently forced to resettle by landlords. Arnol residents had to move their village three times between 1795 and 1853. But, in contrast with contemporary construction, the blackhouse was reparable from any level of neglect and decay, or could be dismantled for re-use. If abandoned, its thatch and mortarless fieldstone walls returned into the soil.

Learning from Lewis

The blackhouse offers inspiration for lower-tech ways out of climate catastrophe. High-technology proprietary systems for reducing operational energy consumption should always be rigorously interrogated by a lifecycle carbon analysis to verify that they will repay their typically high embodied carbon and difficult end-of-life disposal within very few years of operation.

Typical new houses are bigger than the blackhouse at Arnol. Take, for example, the ‘Winstone’, designed around 2010 by David Wilson Homes, built in many locations and climates all over the UK, and marketed as a ‘truly magnificent detached family home’. The two-storey house with its decorative front gable, four bedrooms, and two bathrooms is heated with fossil fuel gas through a condensing boiler. The spaces for living and socialising are significantly larger than the estimated 20m² of the blackhouse kitchen, consisting of an 18m² kitchen with seating area, a 17m² lounge and a 9m² dining room.

Operational energy

The future, like a blackhouse, has to be chimneyless. Free not only of domestic fires and gas boilers, but of industrial chimneys belching out our embodied carbon footprint. The homes we need are neither sooty blackhouses nor pink and buff brick houses in the suburbs built with cement, steel and glass and heated by gas boilers, but rather genuinely green houses: well-insulated, recyclable, reparable and adaptable, in walkable environments.

Now we understand the ecological cost of our energy wealth, we must learn to nurture, repair, retain and appreciate our material world, seeing wear and tear not as a sign of neglect or poverty, but as the proud, beautiful patina of long use. The brand-new detached house built on a greenfield site needs to go from status symbol to comical relic of the bad old days.

The circa 20m² central space around the hearth was both kitchen and living room, used by six people or more for cooking, crafts, socialising and storytelling. It was flanked by sleeping alcoves and the byre. The heated room constituted an island of dry warmth after windswept, often rainy days caring for cattle, tending vegetable plots, working the land, or harvesting fire fuel. Trees were too scarce and slow-growing to furnish fuel, but peat was abundant. Oral history suggests that to provide a year’s heat for one blackhouse took two to four weeks of hard work, cutting peat by hand using a tairsgeir (peat knife), then piling it to dry.

A car-based road layout in Wokingham typical of the kind developed by volume housebuilders

Barnabas Calder is senior lecturer at the University of Liverpool, and head of the Architectural and Urban History Research Group. He is the author of Architecture: From Prehistory to Climate Emergency.

To achieve net zero we must return to low-embodied energy materials wherever possible. Our habitual default materials, such as steel (32-45MJ/kg) and aluminium (175-200MJ/kg) are powerful agents of climate catastrophe.

Away from a New Architecture

The Arnol blackhouse, Isle of Lewis