Housing and Construction
Global warming and Climate Change
The scientific consensus is that most of the warming observed in the last fifty years is attributable to human activity, through emissions of greenhouse gases such as Carbon Dioxide (CO2) and methane into the atmosphere. We need to make a profound change in our use of energy and other activities that release these gases. And we need to prepare for the changes that are now already unavoidable. (UK Sustainable Development Strategy 2005)
Sir David King, UK chief scientific adviser has said “Climate Change is the most severe problem we are facing today”. With the average household producing 6 tonnes of CO2 /yr. and buildings collectively contributing more than half the national out put, it is clearly a target area for savings.
What is Sustainable Building?
Sustainable building is building that is less damaging to the environment than current general practice. It is energy efficient and minimises the use of non-renewable resources. It enhances the natural environment, making use of natural climatic systems and local topography. It avoids the use of known toxins and is careful to involve local people and materials. It actively addresses climate change by minimising emissions of CO2 and greenhouse gases. There are now a number of advisory bodies and documents on sustainable building methods:
- Nationally there is the Code for Sustainable Homes.
- Regionally there is Future Foundations, the Southwest Charter for Sustainable Construction.
- More locally there is the Cornwall Sustainable Building Trust, a county wide organisation that has contributed to both of the above publications.
The planning system is also undergoing the most significant changes since its inception in 1945. County Structure Plans will be replaced by overarching Regional Spatial Strategies (RSS), and the district authority’s Local Plans will be replaced by Local Development Frameworks, supported by Local Development Documents. The RSS will put more emphasis on sustainable construction methods and will lay down minimum requirements for renewable energy contributions to all new developments. Currently the minimum target, which will also rise progressively, is 10% of the developments base load. This will result in more demand for building integrated micro-renewable systems and for more energy efficient buildings. Both of these results will become drivers for more sustainable building methods. There is also a growing call for all new building to be to Zero fossil Energy Developments, i.e. ZED Standards.
The challenge for sustainable design is to achieve a new sympathetic vernacular form that is both in sympathy with its surroundings and inherently low energy. Pre-industrial dwellings would have used exclusively local low energy materials but in recent times attempts to imitate past styles have resulted in materials being transported from developing countries thousands of miles away. Most people now realise that this is not sustainable and local alternatives must be found.
Zero fossil Energy Developments ZED
ZED developments are achievable in all new build situations; whilst existing properties can also be upgraded to the same status by adding insulation, draught-proofing and installing micro-generation equipment. Although more demanding, this can also be achieved with care on some listed buildings. (see National Trust’s Gibson Mill, www.ecoarc.co.uk).
It is also possible to substitute solar panels on top of a roof with solar piping or hot air collection from radiant heat under the slates.
Sustainable buildings need to be airtight and very well insulated; this is not to say that they should not be micro porous with breathing walls. A good analogy is human lungs which are also airtight but gas and vapour permeable.
ZED designs, as well as being very resource and energy efficient, will have inbuilt capacity to generate both heat and cooling and renewable electricity. ZED designs will also have passive heat recovery systems built into their structures, both as thermally dense materials and as natural wind assisted ventilation systems.
Orientation to optimise winter solar gain and to utilise natural landscape and topographic features for shading or cold wind barriers is also a feature of sustainable building design. Computer modelling can be used to simulate light and shadow conditions throughout the year. Good design will also seek to avoid wind tunnels and frost pockets within developments.
Cooling without carbon emissions
Climate Change predicts more hot summers like the 2003 summer that resulted in thousands of older people dying of heat exhaustion. There is already an undeniable need for cooling capacity in buildings. Simplistically this is addressed by air-conditioning but this comes at the price of increased energy use and therefore CO2 emissions.
In order to overcome this sustainable building designs need to incorporate thermal mass in their internal surfaces. This can be in the form of dense materials which both absorb and release heat slowly.
Different designers find different and often novel ways to provide this property in their designs, some utilise water storage tanks or pools in the buildings, some use concrete or stone features and some are now experimenting with new ideas incorporating Phase Change Materials.
Passive Stack ventilation is now fairly common, it uses the natural tendency of rising heat and the venturi effect of air passing an opening sucking out from it. This has been taken further by passive wind assisted ventilation with heat recovery in a system designed by ZEDfactory. This system uses no electricity and only saves energy and carbon whilst providing for both cooling and potential heat recovery.
Whereas passive winter solar gains can be achieved by a southerly glazed elevations, care needs to be exercised to avoid summer overheating. This can be a voided by overhanging eaves, solar blinds or Brise-Soleil, an increasingly common sight on commercial buildings. A more sensitive approach can be from shading with deciduous trees but this is not always possible especially on clay soils where root intrusion can be an issue.
Increasingly severe weather episodes
Climate change is already causing more severe weather of all extremes and buildings need to be designed to withstand new pressures:
- Prolonged drought dictates water efficiency and drought resistant materials, rainwater recycling and possibly grey water as technology improves. Water efficient appliances including spray taps, aerated showers and low flushing toilets are all essential.
- More severe wind and rain outbreaks require robust detailing of all fixings and perhaps a rethink of roofing materials to include resilient sheeting materials, not hitherto common, bigger gutters and more on site attenuation capacity.
- Green roofing systems including succulent planting have the advantage of slowing runoff and increasing biodiversity, whilst holding potable water in the water cycle thanks to transpiration. All green plants also absorb carbon dioxide and can be grown locally.
- With changing climate come changing species and quite possibly local houses are going to have to include mosquito netting to openings.
- Buildings by nature remove the ground’s capacity to absorb precipitation, sustainable buildings have to compensate for this tendency by natural soakaways or wetland areas or what are known as Sustainable Urban Drainage Systems (SUDS), which may also include attenuation swales and ponds or simply permeable ground conditions.
- Ideally developments should be able to contain rainfall from a 1 in 500 yr. event but occasionally and particularly where existing buildings are concerned this is not possible. In these cases developments should be flood resistant, with sleeved and valved utilities, safe entrance and egress routes and provide for non habited ground floors with utilities to first floor levels.
Developers should demonstrate that their scheme meets the needs of the local community, which has been involved and consulted during the design process. Essential information should be provided with each unit explaining:
- Energy and water management and environmental systems.
- Local amenities and transport services and community groups.
- Recycling and refuse collection facilities
- Useful contacts, emergency services, social services etc.
Wherever possible make dwellings and amenities accessible to disabled people above and beyond statutory requirements.
Design homes to be adaptable to future and changing needs, e.g Lifetime Homes/BS8300 standard.
Incorporate features like attic trusses to optimise building footprint and allow for vertical extensions.
Sustainable developments will have provision for community management of facilities and provide public open space, green spaces and provision for food growing either in gardens or allotments.
Developments should also incorporate a private space where residents can be in the open air and not overlooked.
All dwellings should include an area where clothes can be dried naturally.
Homes should be sited within walking and cycling distance of local amenities and public transport nodes.
Provision should be included for the secure storage of cycles.
Sustainable building is just common sense once you have understood the principles:
- KISS - Keep It Simple Sweetheart
- Form should follow function
- All buildings have impacts but sustainable building minimises these and the best examples are truly inspirational and enhance their surroundings.
These pages will be built up topic by topic as simple guidance. This will be an ongoing process, meanwhile here are some useful links:
- www.futurefoundations.co.uk - Southwest sustainable construction charter
- www.cat.org.uk/wise + www.zerocarbonbritain.com - Centre for Alternative Technology
- www.bre.co.uk/sustainable/indexhtml building research establishment
- www.communities.gov.uk the code for sustainable homes
- www.csbt.org.uk Cornwall sustainable building trust
- more to follow!!