A green building debate
Mark Hoare and Bill Dunster
1st June, 2009
Two views on form and function in the green building debate that must be sensitive to the local environment and responsive to the local character, cultural diversity and ecology of its place without diluting its uniqueness.
Sustainable and sensitive
Mark Hoare specialises in designing alterations to listed buildings and new buildings in sensitive settings. He is a trustee of the Prince’s Foundation for the Built Environment and a member of the National Trust’s advisory architecture panel. He is an associate at Robert Adam Architects
Our existing housing stock has poor energy performance, and we must improve it. In other ways the mass of prewar housing is fairly sustainable, often built with local materials and skills, and using materials with low embodied energy. Our traditional buildings are structurally straightforward and capable of fairly easy alteration and repair over time – and this, in part, is why so many old buildings survive.
Houses built before the widespread use of the car have the important advantage that they are often clustered around local facilities and – at least in towns – close to public transport. In a sustainable settlement, day-to-day needs should be found within a five- to 10-minute walk.
This broader context of daily infrastructure has a huge impact on our ecological footprint. According to research by the BioRegional Development Group, in one of the most publicised green developments, BedZED, the largest carbon savings came from the introduction of car sharing and an organic vegetable box scheme.
Of course, the design of individual houses is highly significant in reducing carbon emissions, but the holy grail of zero carbon should not become the principal determinant of design. Our houses are our nests, the places we raise our families, and places of social and cultural significance. There is a danger that in becoming singlemindedly obsessed with carbon, we reduce the design of a house to nothing more than an energy-engineering challenge.
According to basic green design principles, a house should be orientated to maximise winter solar gain and to exclude summer overheating. The internal volume will be configured in the way that best allows cool air to circulate in summer and warm air in winter, with minimal mechanical assistance. Water, energy and waste will all be managed responsibly. Spaces will be made for birds, bats and other wildlife. In many green buildings, these elements of the design work well, but the end result appears over-technological and not really part of its place. Technology (be it high-tech or low-tech) is important, of course, but an overly technological approach tends to be reductionist and tends to edit out subtlety or difference.
A green building must not simply be exemplary in reducing CO² emissions, it must also be robust, adaptable and beautiful if it is not to be demolished prematurely. It must be sensitive to the local environment and responsive to the local character, cultural diversity and the ecology of its place without diluting its uniqueness.
Remaining sensitive to place is challenging, especially as energy performance and airtightness targets become more demanding. Factory detailing is increasingly replacing one-off site detailing, and buildings are becoming more and more alike in how they are put together. Standardisation does achieve higher standards in some respects, and results in economic and carbon savings in the short-term, but factory-finished items tend to be harder to repair in situ and I suspect will prove more expensive in the long term. The use of locally familiar materials, massing, finishes and colours helps considerably in counteracting these homogenizing forces and maintaining the unique identity of places.
Not many of us yet value cultural diversity or local distinctiveness in the way we value biodiversity, but perhaps we should, even if we can’t appreciate their inherent value. It might be hard to believe that a certain way of making gates or thatching ridges or laying hedges might make us more vulnerable in several generations’ time, but we are at last beginning to grasp this notion when it comes to the threatened loss of a butterfly or bird. Are regional traditions of gate-making a quaint irrelevance or might we be glad to have kept them alive some time in the future when we have need of them more than now?
I recently copied a 19th-century gate that I found on a farm close to where I live. It seemed to me to be a brilliant solution not just for keeping our children away from the road, but also for keeping out small deer and rabbits. The gate could potentially be modified into a fencing design at some time in the future when wire netting costs the Earth or cannot be obtained and when small-diameter timber is readily available. My new gate is much more elegant, more sparing in the use of timber and probably more durable than any of the gates on sale at my local builder’s merchant. It is a very simple design but much noticed by visitors.
Traditional design tends to be frugal. It favours low-embodied and local materials that are ideal to build with and repair. It also emphasises good passive design to reduce the need for the latest technology, rather than relying on the latest advances of technology to solve problems created by the design. Natural ventilation, controlled solar gain and night-time cooling are all traditional design strategies that are ultimately more sustainable and easier to manage than higher-tech solutions.
Of course, sustainable buildings may need to accommodate solar panels or heat pumps, but these should be integrated in a way that allows for easy upgrades. Loose-fit design and adaptability are essential ingredients of traditional construction methods– which is why so many older buildings endure.
Many established traditional building materials have high thermal mass but poor insulation value. However, newer materials such as lime-hemp, aerated clay block, aerated recycled concrete, recycled newspaper and sheep’s wool insulations are compatible with and capable of enhancing the energy performance of more established materials. Many of these materials have evolved from traditional technology and been developed by those familiar with the older materials.
A major climate-change challenge is not how to build exemplary new buildings but how we upgrade our existing building stock to achieve our 2050 emissions targets. I suggest that practical solutions for retrofitting existing buildings are most likely to emerge from evolved versions
of our traditional buildings. I also believe that the majority of owners of ‘ordinary’ buildings are more likely to absorb and transfer knowledge from new buildings that have a significant amount in common with (or look like) their own home or workplace.
We are the ‘micro generation’
Bill Dunster is the founder of ZEDfactory, a 20-strong multidisclipinary association of architects, product designers, project managers, engineers, physicists and financial experts, all dedicated to providing viable low- and zero-carbon development solutions.
When Ryanair is folk history, car pools are everywhere and we visit vegetarian greasy spoons in our lunch hours, the UK will have to run itself on the limited stocks of renewable energy available within its national boundaries. If every green grid offsite generation device ever dreamed up by an infrastructure engineer were built – with offshore turbines at minimum spacings over the entire continental shelf – we would still struggle to meet much more than 25 per cent of our current energy demand.
All of the offsite large-scale generating capacity would be needed for our stock of much-loved but energy-inefficient historic buildings, including recent buildings that superficially appear historic. This means almost all new construction needs to meet its own energy-generation needs from renewable energy generated onsite, or the lights start to go out.
In the UK we have approximately 600 dry kilograms of biomass allocated per capita – if we harvest woodland sustainably and compress agricultural waste straw – without losing food production. Shared between home, workplace and public buildings, that amounts to some 250kg per capita to run a household.
This tiny amount is what is needed by an automated wood pellet or woodchip boiler sized to provide top-up winter domestic hot water in a superinsulated ZED (zero-energy design) home built to zero space heating specifications and with solar thermal providing hot water all summer.
Put durable, fit-and-forget monocrystalline photovoltaics on the half of the roof facing south, and enough electricity is generated to meet annual electricity demand up to densities of 50 homes per hectare, a density band that represents 70 per cent of all the homes in the UK.
Higher-density urban developments can run off biomass combined heat and power (CHP) using similar fuel quotas, but only if BedZED standards for the building ‘fabric’ (the inherent qualities of the building materials and their surface configuration used in the construction) are achieved. This suggests that it is not realistic or sensible to claim limited renewable offsite generation capacity for new buildings, as you are effectively stealing an existing community’s rights to a future powered by renewable energy.
It is important that we all understand today the shortage of national and international renewable energy supplies of the future, because we need to apply every renewable harvesting opportunity, both on and offsite, if we are to achieve an equitable, democratic future, and a workable long-term urban fabric with enough communal renewable energy to power public transport and food production and distribution.
Seen in this light – it is irresponsible not to plan new communities around onsite renewable energy generation. It is also fraudulent to pass off low-embodied carbon construction as a valid green building solution without integrated microgeneration.
Our understanding of such technologies is recent, some of the materials are modern, and the physics logic generating the building form will inevitably change traditional aesthetics. This process could be considered as a celebration and an evolution of a new 21st-century vernacular that will absorb elements of tradition, but ultimately produce a recognisable architectural language expressing optimism for a future that works without waste and pollution.
It becomes important to reduce the carbon footprint of the original construction using locally sourced materials and labour, and when combined with building integrated renewables this means that enough renewable energy is harvested over the life of the building to offset the carbon invested both to make and maintain the building fabric, and possibly even a share of a small electric car.
North- or east/west-facing homes use significantly more scarce biomass than a south-facing home with good passive solar gain and blinds and overhangs to prevent summer overheating. A south-facing garden will also greatly increase the productivity of homegrown fruit and vegetables.
Assuming an annual eight per cent fuel-price-rise – not unreasonable as peak oil, peak gas and peak uranium affect limited supplies of finite, non-replenishable reserves – a zero-carbon RuralZED home built today and fitted with ZEDfabric monocrystalline photovoltaic panels will save a typical household £1,000 per year over 10 years – a sum that could make a big difference to the quality of a family’s diet, or indeed their summer holiday.
Let’s welcome a new architecture that helps avoid billions on fighting for fossil fuel reserves outside our national boundaries and avoids the need for the steady erosion of our civil liberties by a police state required to control scary nuclear technologies.
It is the adoption of contemporary patterns of energy and resource consumption within historic building fabric that fuels much of our international aggression for oil reserves. Even if the entire existing building stock achieved a 70 per cent reduction in energy demand through radical energy-efficient renovation, it would use up the entire stock of available national communal energy reserve even at the most optimistic 2050 levels.
This makes it critically important that when we are lucky enough to design a new building it does not further erode the limited national renewable energy reserves.
If an architect proposes to hide solar panels behind a parapet invisible from the street, or formal stylistic concerns start to create poor solar access, poor daylight and overshadowing or windshade, the energy-generation problems are automatically sent offsite to centralised fossil fuel power stations or worse.
It is almost impossible to fit meaningful levels of solar panels on, for example, a ‘Georgian’ Bloomsbury five-storey urban block typology at relatively high city-centre densities. So, yes, orientation is less critical at high densities, and city centres need to be allocated larger biomass quotas. However, the top three storeys of any city can easily be powered by the renewable energy harvested by the building envelope (the surface that provides shelter from the elements and encloses the internal volume), providing solar access, ventilation, daylight and wind are optimised by the urban form.
This strategy alone could reduce the demand on scarce national energy reserves by 60 per cent, allowing scarce biomass stocks to go further. The architects of the past have no monopoly on beauty, natural materials, elegant proportions, walkable neighbourhoods or mixed-use streetscapes, and all of the qualities required by the highest standards of contemporary place-making can be expressed within a new climate-responsive solar urbanism that is firmly rooted in our time.
We need to encourage this new contemporary vernacular which does not apologise for embracing renewable energy technologies or require big, expensive energy infrastructure CHP and district heating investments that just are not going to be funded in a recession.
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