5. Resource Conservation
A major aim of sustainable housing must be to exploit all viable opportunities to recycle and reuse products and buildings in order to reduce production in the first place. It cannot be stressed too strongly how important it is to look at each housing development’s potential for efficient and responsible resource use within its own unique and local context (Figure 5.1).
This Chapter offers guidance on the following key areas for resource conservation:
- local sourcing
- waste minimisation
- embodied energy and environmental impact
- lifecycles of buildings, products and materials.
5.1 Local Sourcing
Figure 5.1 Traditional Scottish housing uses local materials and detailing to suit the local climate.
Figure 5.2 Long distance transportation of construction materials has a detrimental impact on the environment and people’s health through pollution and noise.
Specifying products and materials which are sourced and/or manufactured in the locality of a housing development brings the following benefits (see Case Study No. 2):
- less environmental impact in terms of transportation
- direct relationship between housing providers and the local economy
- easy visiting and monitoring by specifiers who wish to verify the sustainability of products
- local employment linked to the housing development
- increased sense of community through local connections.
It is not always possible to obtain local products and materials which provide the same quality and performance as imported products for a similar cost. Where local sourcing is possible, care must be taken not to contravene free-trade agreements within the European Union. Specifiers should ask for products in terms of a performance specification. It is then possible to write in “local availability” and “minimum transportation” clauses (with a stated distance) as one of the performance requirements. An alternative to this would be to write the performance requirement to match the exact specification of the local product, paying attention to any unique features it may have.
Did you Know?
New housing today is generally designed to last only sixty years. Much of Scotland’s older housing has lasted over 120 years, saving a significant amount of resources over its lifetime compared to today’s relatively short life housing.
Box 5.1 Local sourcing: pointers for good practice
ask contractors and consultants to source materials and products which are available locally and find out how they intend to do so
weigh up the use of local resources against their potential environmental impact both globally and locally
use performance specifications with clauses which favour local sourcing
source raw and bulk materials as locally as possible to minimise transportation
Figure 5.3 If stone cannot be recycled it is best to source new materials as locally as possible.
Figure 5.4 Re-used stone minimises our use of non-renewable resources and should be specified when available.
Table 5.1 Sourcing local information
| Environmental Factor | Site Level Sourcing | Local Sourcing Information | Global Impact Information |
|---|---|---|---|
| 1. Raw materials consumption | sustainable use of natural resources on site |
local manufacturers Yellow pages local trade organisations |
manufacturing associations environmental groups such as Friends of the Earth reports government reports and websites |
| 2. Biodiversity / Flora and Fauna | Site audit Website for Scottish indigenous flora | Scottish Natural Heritage -Local Office |
manufacturer product information - effect on global
scale
reports by environmental groups such as World Wildlife Fund, Scottish Wildlife Trust Scottish Natural Heritage -main Office in Edinburgh |
| 3. Toxic emissions to air, water and earth | site audit for ground, air and water contamination; historical maps, previous site records | SEPA environmental health departments |
manufacturer product information LCA systems for product impact |
| 4. Water consumption |
site audit of natural resources water authorities |
SEPA Water authorities meterological Office for rainfall details |
manufacturer information environmental groups |
| 5. Energy use | site audit of available renewable resources: sun, wind, water, biomass, geo-thermal |
local energy companies local audit of waste heat resources for CHP/district heating identify energy partnerships |
embodied energy manufacturers product information and independent audits |
| 6. Solid waste |
site audit for re-use/recycling of waste matter re-use/recycling of existing building materials |
other local reusable/recyclable material available? salvage yards SEPA Local Authority |
manufacturer product information LCA systems for product impact environmental group reports |
| 7. Health impacts | site audit for health impacts: noise pollution, electromagnetic radiation etc. |
Local audit for potential health impacts environmental health department Health Authorities |
manufacturers product information and independent audits by environmental groups |
| 8. Economic impacts | audit of surrounding area around site for local manufacturing of construction products |
local enterprise companies to identify local
construction manufacturing companies establish partnerships with local authorities |
manufacturers information on global economics environmental group reports on products |
| 9. Social impacts | consult users adjacent to site and on site |
consult local community groups Local Plans |
manufacturers product information on social impacts |
5.2 Waste Minimisation And Pollution
The five main areas of waste to address are:
Figure 5.5 Contractors should be required to implement waste minimisation strategies to prevent this.
- construction waste
- prefabrication
- re-use and recycling
- water conservation
- domestic waste.
5.2.1 Construction waste
Prevention of waste in the construction of housing can save considerable amounts of non-renewable resources. Housing providers can encourage good site practice by requiring waste minimisation strategies to be provided and used during the construction process by the contractor (see Case Study No.2). These should be referred to in housing design guides and requested in contract documentation1.
5.2.2 Prefabrication to minimise waste
The Egan Report2 has set targets for reducing defects by 20% and costs by 10% in the construction industry and has suggested that prefabrication can go a long way to achieving this. The main advantages of prefabrication are:
- factory controlled conditions for manufacture minimising the effect of weather
- standardised units with minimum offcuts
- quick assembly with greater precision
- just in time delivery requiring minimum site storage
- minimised defects.
Figure 5.6 Prefabrication gives factory controlled precision on site.
Prefabrication in housing can take the form of timber, steel and concrete units which incorporate fully finished secondary elements such as glazing, services and finishes. The units can vary from simple non-loadbearing cassettes (Figure 5.6) that form walling, flooring or roofing, to comprehensive load-bearing systems that come as a complete package. There are a number of proprietary systems on the market which housing providers can specify (see Case Study No.6)3. Ideally, prefabrication should occur as locally as possible to minimise the impact of transportation and link local knowledge with the technology used. In some cases the additional transportation impacts of non-local sourcing may outweigh the benefits. Care must be taken to ensure that the proprietary system is robust enough to meet the local climate conditions of the site chosen.
Did you Know?
Up to 30% of construction materials on site are wasted and re-ordered through poor detailing and site practice.
5.2.3 Re-use and recycling
Both re-use and recycling have a major role to play in the minimising of resource use and waste. The European Protocol on Waste makes it clear that the preference is for reuse, which means using less resources and minimising waste, rather than more energy-intensive recycling processes which may consume more resources:
Figure 5.7 The best option of all is to reuse buildings (St. Peters Court, Aberdeen, Castlehill HA)
- Re-use whole building (best option). see Figure 5.7.
- Re-use components
- Recycle components
- Burn components to obtain energy
- Dump components in landfill (worst option)
Current Scottish practice is to have recourse to the landfill option, rather than any of the other four strategies, with 92% of solid waste going to landfill4. This is unsustainable in the light of incoming EU directives on minimising waste and the increasingly onerous tax on landfill levied in response to these.
| Environmental Impacts | 1. re-use building | 2. re-use components | 3. recycle components | 4. burn components | 5. dump components |
|---|---|---|---|---|---|
| 1. Raw materials consumption |
minimal some remedial treatment will be required |
fairly minimal requires resources to prepare and clean |
depends on processes |
high component requires complete replacement some energy resources saved |
very high component requires complete replacement |
| 2. Biodiversity/Flora and Fauna | minimal disturbance |
minimal possible transportation impacts |
transportation impacts possible emissions |
potential toxic emissions transportation impacts |
takes up precious land cover and displaces flora and fauna |
| 3.Toxic emissions to air,water and earth | minimal unless building is energy inefficient |
minimal possible residues from cleaning |
emissions at recycling plant | emissions to air | emissions to earth and water |
| 4. Water consumption | minimal | required for cleaning purposes |
can be high depends on processes |
minimal | minimal |
| 5. Energy Use | minimal unless building is inefficient |
minimal required for preparation |
fairly high can be as high as original manufacturing requirements for certain plastics transportation |
energy gain transportation |
required to service landfill site transportation |
| 6. Solid Waste | minimal providing demolition is not excessive | fairly minimal | depends on process | minimal | very high |
| 7. Health impacts | minimal providing building is efficient and safe | minimal cleaning and preparation may involve chemicals |
possible emissions at processing plant possible chemicals introduced to recycled products transportation |
emission to air of potentially harmful compounds transportation |
potential leakage of toxic residues transportation |
| 8. Economic impacts |
minimal restoration can help retain local economy |
can be more expensive than new components additional labour costs for preparation and cleaning helps retain local economy |
can be cheaper than reuse artificially low costs can help retain local economy if processing is local |
can substantially reduce fuel costs for heating in the short term (will run out in long term if waste minimisation followed through) | increasing taxation is making this less economically attractive |
| 9. Social impacts |
preserves historical continuity and local knowledge in the area use of local labour |
partial historical continuity and local knowledge in the area
use of local labour |
can confuse identity of materials (plastic “wood”) can introduce new beneficial materials |
can help reduce fuel poverty in short term | highly undesirable and unsightly |
An informal economy dealing with re-used construction products already exists in Scotland with various salvage and demolition contractors (Figure 5.8) supplying both high grade and low grade construction materials and products5.
Figure 5.8 Housing providers can store materials for re-use either on site or in a special store.
In Scotland, timber, roofing slates and tiles, bricks and blocks in a low-cement mortar are all suitable for re-use and are often of a higher quality than equivalent new6. Current contractual practice and economics, however, do not always favour the re-use of materials.
One obstacle to the re-use of materials and products is the guarantee of fitness for purpose (Figures 5.9, 5.10). Where a material is to be used structurally, it will require testing for integrity. There is equipment available to carry out such tests7. Non-structural use does not require such onerous testing and visual inspection will often suffice. Certain insurers may, however, require stringent evidence of fitness for purpose. At present there are still no British Standards or building regulations covering the re-use of construction products and materials. This puts the burden of proof on the specifier who may be restricted by professional indemnity requirements. Despite these obstacles, specifiers have successfully incorporated re-used materials into housing products (see Case Study No. 3)8 (Figure 5.11).
Figure 5.9 Re-used door being re-finished to satisfy fitness for purposes.
An important design principle when specifying re-used materials is to allow time for sourcing the re-used material at the outset of the design stage and allow a degree of flexibility in the design detailing to accommodate what material is found. This has implications for the programming of a housing development and should be borne in mind at the feasibility stage. It may be necessary to negotiate an extended design programme with housing funders in certain cases.
Box 5.2 Waste minimisation in construction: pointers for good practice
follow European Recycling protocol with preference for re-use over recycling
ask contractors to provide waste minimisation strategy for construction process
investigate use of prefabrication, preferably from local manufacturers
carry out a site audit to identify existing elements for re-use and recycling
re-use as many existing elements on a site as possible
specify materials and products with the potential for re-use and recycling
if a site audit reveals no re-useable materials, try to source re-useable or recycled materials from the locality
strike a balance between sourcing re-used materials and the distance required to transport them
long distance transportation of bulk items should be avoided
allow time for sourcing reused materials and products in development programmes
allow design to accommodate re-used products and materials in construction.
5.2.4 Water conservation
Figure 5.10 Re-used door being re-finished to satisfy fitness for purposes.
The need for water conservation is not currently at the forefront of most housing providers’ or occupiers’ requirements. Some rivers are, however, already at their limit of extraction (Figure 5.12) due to the increasing use of water by business, industry and housing. Pressure on water supplies is especially high in the drier Eastern parts of Scotland (Figure 5.13). Housing providers can respond effectively by minimising use of water. Where water authorities have no plans to meter water, meters should be installed by housing providers to raise occupiers’ awareness of the amount of water that is being consumed and the resources required to deliver it. Real water savings can occur when occupiers pay for what they use.
Figure 5.11 Bricks can easily be re-used in landscaping and the building (Glenalmond Street, Glasgow Case Study No 3.)
Figure 5.12 This river is at the limit of extraction already. Any additional consumtion by human use will damage the precious ecosystem served by it.
Baths, showers and toilets use the majority of domestic water and are the priority for water saving. Simply specifying water conserving sanitary fittings can save up to 30 per cent of domestic water consumption. These can include spray taps, low-flush toilets and showers above baths or as a separate item from the bath. Power showers should be avoided as these can use nearly as much water as a bath if used excessively.
| Usage | % |
|---|---|
| flushing the toilet | 33% |
| washing machines | 21% |
| baths and showers | 17% |
| kitchen sink | 16% |
| washbasin | 9% |
| dishwasher | 1% |
| hosepipes | 3% |
Did you Know?
The average domestic consumption of water per person in Scotland is around 180 litres per day. 1,000 - 2,500 children die each hour in the world due to lack of clean, safe water.
Rather than use water from the mains supply to flush toilets, waste shower and bath water can be used instead. There are now a number of proprietary systems available for recycling grey water (Figure 5.14) although they form a significant cost over and above standard housing costs and may require prior approval from regulatory authorities (see Case Study No. 2)9. It is not advisable to recycle sink water as this may contain toxic residues from cleaners and paints as well as excessive amounts of cooking oils.
Figure 5.13 Some parts of the east of Scotland may experience water shortages. (©SEPA 1996)
Water conservation can also be achieved by collecting rainwater for drinking in areas with relatively good air quality. This has been carried out successfully in the UK but is perhaps more applicable to non-mains rural areas where spring water may be more unreliable and rainwater is cleaner. At the very least, rainwater can be safely collected from the roof in water butts at the base of drainpipes for use in the garden.
Box 5.3 Water conservation: pointers for good practice
Did you Know?
The use of composting to reducing organic waste is growing. Aberdeenshire Council has planned to have all household organic waste communally composted within 5 years.
install water meters to raise awareness and save water
minimise use of water - use low flush toilets and spray taps, install shower
recycle greywater - bath and shower water is adequate for flushing toilets (Figure 5.14)
collect and recycle rainwater on site - use water butts to collect water off roofing for the garden
collect rainwater from roofs to supplement drinking water in areas where the air quality is good and water supply is poor
roofing and all associated flashings and pipework should be lead-free when collecting rainwater for drinking water
5.2.5 Domestic waste
Organic matter makes up to 50% of household waste. Given the intense pressure on landfill and the undesirability of incinerating waste, it makes good sense to encourage individual and communal composting of organic waste. Provision should be made on site for compost areas and these should be carefully designed for good composting conditions. The volume required per household is approximately 2m3. Additional provision for compost storage is also required in kitchens, ideally a small removable bucket size sealed container under the sink.10
Figure 5.14 Proprietary greywater system.
Figure 5.15 Compost is already separated and collected in Germany. Housing providers should ensure there is space allocated for such initiatives.
Opportunities for recycling and re-use of domestic inorganic waste should also be maximised. This has design implications in terms of extra storage required both inside and outside for storing potentially re-usable or recyclable items until they are uplifted by local recycling/re-use schemes.
5.2.6 Sewage
Every day the Scottish population produces over one million cubic metres of raw sewage containing 110,000 tonnes of solid matter. The EU Urban Waste Water Treatment Directive to be implemented between 1998 and 2005, places severe demands on local water authorities to improve standards of treatment in an already overstretched system.
Figure 5.16 Reedbeds can be used to break down sewage naturally in rural housing schemes (Trossachs Time Share Apartments - Watershed Systems).
Housing providers have a useful role to play in minimising sewage discharge, particularly in rural areas where local sewage systems may be at capacity. The use of rural or suburban wetland systems with minimal energy input can minimise sewage discharge11. A wetland system consists of a number of treatment ponds which are filled with natural plants, such as reeds, that break down and transform the sewage into harmless compostable matter than can be directly applied to the land. There are already a number of schemes successfully running in Scotland12 (Figures 5.16-5.17). Less intensive wetland systems can also be used to “polish” grey water which has been recycled or directly discharged from the dwelling. The result is clear water which can be safely discharged into the natural environment. Not all authorities accept wetland treatment of sewage and it is important to seek approval from SEPA for discharging the clear water into existing water courses.
Figure 5.17 This natural sewage treatment plant serves up to 500 people and can serve rural housing schemes requiring autonomous servicing. (Living Machine Findhom)
Figure 5.18 The sludge discharged from this pipe is a by-product from the manufacturing process of PVC. Specifing low toxic materials minimises these problems, which are not “visable” from the housing scheme itself.
5.3 Embodied Energy And Environmental Impact
Did you Know?
Embodied energy can add up to 50% of the overall energy use for a highly energy efficient house over a 30 year period.
The construction life cycle for housing (Figure 5.19) shows the different stages that need to be considered for overall environmental impact analysis. It is increasingly important to look at all stages of the construction lifecycle as housing becomes more energy efficient. Calculating the total embodied energy required to take construction materials and products through a complete housing life cycle involves:
- extraction
- production
- transportation
- construction
- maintenance
- deconstruction
- waste management
Figure 5.19 Construction life cycle for housing showing all the stages that need to be considered to ensure sustainable construction of housing.
Calculating embodied energy is complex and usually omits maintenance, deconstruction and waste aspects because these are too site specific. Figures can only be used as an order of magnitude and usually only relate to the volume or weight of a material rather than the comparative amount required for the same building element such as a wall. No account is taken of the ability of a material to be reused. Transportation of materials also plays a significant role in embodied energy calculations where dwellings are remote. Nevertheless it is still a useful pointer to the overall environmental impact of a material or product.
| Material | kWh/m3 |
|---|---|
| aluminium | 103,000 |
| steel | 75,600 |
| plastics | 47,000 |
| glass | 23,000 |
| imported softwood | 7,540 |
| clay tiles | 1,520 |
| bricks | 1,462 |
| plasterboard | 900 |
| concrete tiles | 630 |
| concrete | 600 |
| local slates | 540 |
| mineral wool (loose) | 230 |
| local softwood | 110 |
The best approach for housing providers in relation to embodied energy is to employ basic principles (See Box 5.4) rather than generic lists of figures. Consultants should be encouraged to obtain embodied energy ratings from manufacturers where possible for comparison.
Figure 5.20 Specifying timber from unsustainable sources will result in barren land such as this in Scotland.
A more comprehensive analysis of the environmental impact of a material or product can be obtained from a full Life Cycle Analysis (LCA). Each stage of the life cycle of a construction material is examined for a number of environmental impacts.
Factors in Life Cycle Analysis
- Raw materials consumption
- Biodiversity/Flora and Fauna Ecology
- Toxic emissions to air, water and earth
- Water consumption
- Energy use in manufacture and use
- Solid waste
Did you Know?
Some local authorities in Scotland already have storage yards for re-usable construction materials.
Key issues at present in terms of environmental impact are preventing deforestation through unsustainable harvesting of timber and avoiding ozone-depleting materials in construction (Figure 5.20). Guidance is available on both these areas.13 LCA is still a developing field and can seem bewildering to most housing professionals. There are, however, a number of very useful services and publications providing independent comparative environmental information on products which housing providers can draw on14. As with local sourcing of products and materials, housing providers should encourage consultants to build up their own databases on environmentally friendly products.
Box 5.4 embodied energy and environmental impact: pointers for good practice
demand comprehensive environmental impact information from manufacturers
use independent sources of environmental impact assessment where possible
treat embodied energy figures with caution and in terms of order of magnitude only
use natural, renewable materials as much as possible for lower embodied energy
allow for transportation, recycling and re-use factors
for the same product, local manufacturing sources generally use less embodied energy
use highly processed embodied energy products such as metal and plastics sparingly
recycled and reclaimed products have relatively low embodied energy
ask consultants to build up a database of environmentally friendly products
5.4 Longevity Of Buildings, Products And Materials
By increasing the longevity of buildings, products and materials, housing providers are effectively conserving resources that would otherwise be used for new construction and new products. There are three factors to consider for extending longevity:
- designing building elements to be re-used
- durable buildings, products and materials
- designing flexible dwellings (see Section 1.2.3)
5.4.1 Designing building elements to be re-used
Figure 5.21 External insulation systems which are bonded together are very difficult to recycle.
Construction components are increasingly bonded together with glues, resins and mechanical fastenings that make it difficult to reuse or recycle them effectively. An example is the use of sandwich products such as insulation bonded to fibre glass mesh bonded to a polymer render finish (Figure 5.21.). These should be avoided where possible and a system of layered construction adopted instead.
Figure 5.22 Housing providers should insist that contractors reclaim re-usable items when demolishing or altering existing housing stock.
Once design for sustainable deconstruction is adopted, existing components can be re-used in future developments generating both cost and resource savings. Timber re-use, for example, is greatly facilitated through the use of screws and bolts rather than nailing.
Where deconstructed materials cannot be immediately re-used, housing providers can set up their own storage yards on land designated for general storage purposes (Figure 5.22). These should contain any materials surplus to requirement which can then be advertised for sale to other developers.
Box 5.5 Re-use of construction components: pointers for good practice
- Design whole dwelling for deconstruction using:
-
- small, easy to handle components
- modular sizing
- removable fixings
- robust, removable materials and components
- layered components rather than bonded ones
- identified storage areas for deconstructed materials
5.4.2 Durable buildings, products, and materials
Figure 5.23 Traditional buildings provide good examples of protection detailing and robust materials to cope with the tough Scottish climate helping them to last for hundreds of years.
Typically new build housing developments are designed to a lifespan of 60 years when they could easily be designed to last 100 or even 200 years (Figure 5.23). Refurbishment schemes often have an even shorter designed lifespan of 30 years, even though the building may already be three times that age. Using durable materials and products for housing reduces the amount of raw material resources required to service housing over its lifetime.
Tough, hard wearing and weatherproof materials should be used on the most exposed parts of the building in accordance with the local climate. Detailing should provide maximum protection of the material from the elements.
Some materials are inherently durable but also use significant amounts of energy to manufacture. A careful balance needs to be struck between these two factors to ensure minimum environmental impact overall.
Box 5.6 Longevity of dwellings: pointers for good practice
design components and materials for re-use
design with durable detailing
use durable products and materials
balance durability of products against their overall environmental impact
design flexible spaces for changing spatial requirements of people living in them
use principle of “lifetime homes” and design for requirements of all age groups (see Section 1.2.3
allow detailing and layout to accommodate users with special needs
consider adaptation possibilities for ethnic and other minority groups with special requirements
Resource Conservation Checklist - Key Areas
specify locally sourced materials and products (see Section 5.1)
use performance specifications to obtain the precise goods required (see Section 5.1)
minimise construction waste (see Section 5.2)
minimise water consumption (see Section 5.2.4)
provide for re-use and recycling of buildings, products and materials (see Section 5.2.3)
minimise embodied energy (see Section 5.3)
minimise environmental impact (see Section Section 5.3)
increase longevity of buildings, products and materials through design and specification (see Section 5.4)
allow for additional internal and external storage for composting organic waste (see Section 5.2.5)
provide facilities for separation and storage of recyclable household waste (see Section 5.2)
consider natural processing of sewage on rural/suburban sites (See section 5.2.6)
Footnotes
^ 1. CIRIA (1997, 1998a, 1998b) gives excellent guidance to contractors on waste minimisation.
^ 2. Egan Report (1998)
^ 3. Ayrshire metal products supply steel frame housing panels (see Case Study No. 6), Filcrete Ltd supply a timber panel system called Masonite (see Case Study No. 2).
^ 4. SEPA 1996.
^ 5. Salvo is the national organisation co-ordinating re-use in the UK. Their web site is www.salvo.co.uk and their bi-weekly magazine contains listings of live demolition sites. Two main suppliers of re-used products and materials in the Central Belt area are Retrovious in Glasgow and EASY (Edinburgh Architectural Salvage Yard).
^ 6. Liddell et al (1994) show which materials and products can be re-used.
^ 7. Salvo can provide information on testing.
^ 8. One of the most successful in this field is the architect Rod Hackney who has developed several housing schemes re-using local brick and slates in Staffordshire. See also CIRIA (1999) for other case studies.
^ 9. See Hall and Warm(1998) for a list of suppliers.
^ 10. See Roulac (1995) for an introduction to composting in housing. Further advice on composting requirements is available from the HDRA
^ 11. Grant et al (1996)
^ 12. for information on wetland systems in Scotland contact “Living Water” in Edinburgh, or Watershed Systems Ltd, Edinburgh. Alternatively, CAT (Centre for Alternative Technology) publish guidance on reed beds systems
^ 13. for guidance on sustainable timber specification see Forest Stewardship Council Scheme which is promoted by the Forestry Commission and other timber associations. for guidance on non-ozone depleting materials see Hall and Warm (1998)
^ 14. ACTAC (1998) Hall and Warm (1998) Anik (1996), BRE (1998) are all useful sources for comparison.