In July 2007 a authorities policy papers called Building a Greener Future declared that all new build places would increasingly work towards going net nothing C by the twelvemonth 2016 as depicted in Fig 14.
Fig 14: Timeline path to conformity. Beginning: Zero Carbon Hub 2009
In order to run into authorities marks the building industry must place and cut down where possible the causes of harmful emanations being released into the ambiance. Harmonizing to Crane Environmental ( 1999 ) in the study entitled Sustainable Homes: A Guide for Registered Social Landlords, edifices are the greatest beginning of energy demand in the UK of which houses account for about 30 % of national energy ingestion. Figures from HMSO ( 1998 ) show that 580 million metric tons of CO2 emanations were released into the ambiance in 1990 due to energy ingestion from places and offices. However it non merely takes energy to run a edifice but it besides takes energy to bring forth the stuffs used to construct it.
The Green Consumer Guide ( 2007 ) underscore the significance of building stuffs in cut downing CO2 emanations from new build building undertakings and urge increasing the usage of sustainable stuffs. The significance of the environmental impact of stuffs is examined by Kruse ( 2004 ) who concludes that the extraction and production of edifice stuffs have a immense impact on the environment with the production of cement entirely lending in surplus of 5 % of planetary CO2 emanations. This is backed by Roaf ( 2007 ) who indicates that the production of cement and steel history for 10 % of planetary CO2 emanations.
4.1 CO2 Emissions
As the overruling accent of the research is to find whether or non the public presentation of lumber framed lodging is an betterment over traditional brick and block building so clean renewable energy solutions such as solar panels, photovoltaic ‘s, heat pumps and air current turbines will non organize portion of the research. Therefore the research into CO2 emanations will be related to the stuffs themselves.
There is no argument that if CO2 emanations from new build lodging are to be reduced so stuffs must play a important function. This is emphasised by the Green Consumer Guide ( 2007 ) and backed by Bed Zed who claim to hold reduced emanations by 25 % in the development wholly through stuff choice and specification.
Sing the transit of building stuffs entirely so Lazarus ( 2007 ) concluded for the Bioregional Development Group that 30 % of all route cargo in the UK is the draw of building stuffs with every 100 metric tons of stuffs being moved a distance of 10 stat mis a sum of 91kg of CO2 emanations are produced. However before stuffs can be transported to building sites they foremost must be manufactured, extracted or refined all of which consume energy and hence contribute towards CO2 emanations. This usage of energy to bring forth stuffs is known as the corporal energy. This corporal energy is considered by National Green Specification ( 2010 ) as being ;
“ the entire primary energy consumed which would usually include extraction, fabrication and transit. Ideally the boundaries would be set from the extraction of natural stuffs until the terminal of the merchandises lifetime, known as ‘Cradle-to-Grave ” .
In its simplest footings embodied energy is described by Crane Environmental ( 1999 ) as the energy needed to transform a merchandise from natural stuffs in the land into the completed concluding stuff. Thus the corporal energy of a house can be deemed to be the entire energy needed to construct the house which can non be recovered during the life-time of the edifice, no affair how expeditiously it operates.
Traditionally in the past edifice stuffs were autochthonal to the local country and grounds of this exists all over the UK with illustrations such as granite being predominately used in Aberdeen whilst sandstone was extensively used in Glasgow. The usage of local stuffs ensured corporal energy was comparatively low as the stuffs were sourced and processed locally understating conveyance and other associated energy costs. This has changed dramatically in that stuffs are now sourced from all over the universe with a premier illustration being that slate is imported from China for usage in roofs as opposed to traditional Scotch or Welsh slate. Transporting stuffs from the other side of the universe increases the energy used to hold the stuff available for usage on a edifice site. This is done for grounds of cost entirely with no consideration to the environment.
If embodied energy is considered as the energy required for pull outing, fabrication and transporting a stuff so this energy can be calculated and used as a tool to stipulate stuffs which are low in corporal energy. Normally the corporal energy is expressed as CO2 per unit mass ( kgCO2/tonne ) or CO2 per unit country for a completed edifice ( kgCO2/m3 ) .
To this terminal BRE ( 2008 ) have created the “ Green Guide ” which is a list of generic edifice stuffs with deliberate informations relative to a stuffs environmental certificates leting designers and interior decorators to be able to do nonsubjective picks sing stuffs cognizing that the stuff is suited to the demands of the development and the environment. This proved to be a ambitious construct as different stuffs can hold similar structural capacities but different multitudes. However the Green Guide is now deriving impulse and is referred to by codifications such as the Code for Sustainable Homes. In order to do the usher user friendly the stuffs are rated on a scaling strategy which lists a stuff as A+ , A, B, C, D and E with A+ evidently being the best rated in footings of the environment.
As the research has shown it takes energy to bring forth edifice stuffs with some stuffs holding more corporal energy than others. Conversely to incarnate energy some stuffs posses internal energy stored in the stuff which can be released through burning or chemical processing, a good illustration being that lumber Burnss supplying energy in the signifier of heat. This type of energy is described in a Guide for Registered Social Landlords ( 1999 ) as built-in energy and must be factored into the environmental equation when stipulating stuffs to give a more rounded position to stuffs overall energy public presentation.
By sing deal as an illustration so the built-in energy will be high as the wood can be burned for energy. This degree of built-in energy is fixed as it does non depend on location, transportatation or processing as lumber is timber the universe over, nevertheless the corporal energy will alter significantly from a place grown lumber to an imported lumber therefore the net energy will alter as the energy to transport the lumber is non recoverable. Therefore there is an of import relationship between inherent and corporal energies which merely add to the confusion for specifiers as to what stuffs should be used to understate emanations.
At this point in the research it should be pointed out that the corporal energy of a edifice is far less than the energy used to run the edifice for warming, illuming, hot H2O etc and hence the emanations from general usage will outweigh those of stuffs. This is emphasised by BRE who conclude that the environmental impacts of the stuffs in a house are less important than the existent public presentation of the house over its life-time with domestic family energy ingestion accounting for 29 % of the UK ‘s CO2 emanations whereas the stuffs used in a house ‘s building history for merely 2-3 % . However as antecedently stressed the purposes of this research are underpinned by stuffs in the method of physique and non the subsequent operation of the construction.
Brown and Buranakarn compared the entire life-cycle energy required to do major edifice stuffs with the consequences shown in Fig 15. As can be seen Aluminium required the greatest sum of energy with lumber being the lowest. However this points to the trouble as discussed by BRE in specifying the energy used from stuff to stuff as although steel carnivals rather ill in the tabular array utilizing more than 4s times the energy of lumber the strength of steel is far superior to timber hence a smaller cross subdivision of steel will back up the same burden as a greater subdivision of lumber therefore the existent application of the stuff must be considered and on some occasions although limited in figure steel could out perform lumber ( Boyle 2005 ) .
Material
Emergy: Ten 109 solar energy J/g
Wood Lumbar
0.88
Concrete
1.54
Cement
1.97
Clay Brick
2.32
Ceramic Tile
3.06
Glass
2.16
Steel
4.13
Plastic ( PVC )
5.85
Aluminum
12.53
Fig 15: Material Extraction & A ; Energy Intensity of Building Materials
With respects to timber framed lodging so UKTFA concludes that the lowest corporal energy of new build lodging is achieved by utilizing lumber frame provided that the lumber is locally sourced and that it can be built off shoal, excavated heap foundations, which are the least energy-intensive foundation type.
This is backed by the Forestry Commission ( 2006 ) who emphasise that by utilizing locally produced sustainable lumber for the structural frame and facing of a house as opposed to brick and barricade the CO2 emanations could be reduced by every bit much as 86 % by cut downing the corporal energy attributed to building stuffs. Further grounds comes from Wood for Good ( 2007 ) who are of the sentiment that lumber frame building could be critical in the challenge of cut downing emanations. The possible for decrease of CO2 emanations possible by constructing lumber framed houses in comparing to traditional edifice methods and stuffs can be seen in Fig 16.
Fig 16: CO2 Emissions of Wall Compositions Source: BRE 2008
Keies:
B & A ; DB Brick and Dense Block
B & A ; TF Brick and Timber Frame
RDB & A ; TF Rendered Dense Block and Timber Frame
B & A ; AB Brick and Aerated Block
RAB & A ; TF Rendered Aerated Block and Timber Frame
SC & A ; TF Softwood Cladding and Timber Frame
Extra benefits of lumber as a edifice stuff are detailed by Trada ( 2009 ) who are of the sentiment that lumber
is the most various constructing stuff presently available as it can be used in a assortment of applications such as ; structural model of lumber kits, insularity in the signifier of cellulose fibers, internal and external coating of houses for shocking or cladding and can even be used for furniture. They add that it is besides the ultimate in ‘green ‘ stuffs, being:
Renewable – every bit long as replanting is carried out in line with sustainably managed woods so timber will ever be available as a renewable stuff. In Europe, where over 90 % of UK timber originates it is current pattern in FSC woods for two trees to be planted for every one that is felled.
Natural. Merely limited energy and processing is required to change over felled lumber into a useable building stuff with the energy frequently coming from bio energy from waste wood and off-cut stuff.
Reclaimable and reclaimable. Timber can be burnt for fuel and it will besides bio-degrade. One of the large growing countries for recycled wood is biomass.
The UK Timber Frame Association ( 2009 ) position lumber frame as the most environmentally friendly commercial edifice stuff available mentioning lumber as being ; renewable, organic and non-toxic, whilst merely necessitating low degrees of corporal energy to fell procedure and conveyance. They have besides calculated that in a typical lumber framed house there will be about 12 to twenty three-dimensional meters of lumber, tantamount to the soaking up of about 14 metric tons of CO2. Therefore every bit small as a 10 % rise in the market portion of lumber framed lodging could potentially cut down CO2 emanations by 100s of 1000000s of metric tons.
This feel good factor refering lumber frame is non limited to the UK as the European Commissions DG Enterprise ( 2003 ) are besides of the sentiment that lumber will play a critical function in the challenge against clime alteration saying that:
“ Greater usage of wood merchandises will excite the enlargement of European woods and cut down nursery gas emanations. The committee is analyzing ways to promote these tendencies ” .
As can be seen from Fig 16 stuffs traditionally used in the building of new lodging such as brick and block fare the worst in relation to CO2 emanations. One of the major drawbacks of these stuffs is the usage of cement to bond them together. Harmonizing to Pritchett ( 2003 ) 10 % of all planetary CO2 emanations are attributable to the industry of cement, therefore it can non be considered as an environmentally friendly building stuff. Further estimations from Pritchett ( 2003 ) indicate that in the part of 3000 million bricks are being produced in the UK entirely for building usage and every bit long as houses are built by these methods so the energy associated with the industry of the stuffs will stay high.
To their recognition the British Cement Association realised that some signifier of action was required to non merely cut down the corporal energy of cement but to guarantee its length of service as a mainstream edifice stuff for future coevalss ( Collins 2003 ) . To this terminal they have invested in new engineering taking to efficiency betterments of 25 % from 1990 degrees until 2010 as shown in Fig 17.
Fig 17 Reduction in Energy Consumption to Manufacture Cement
However this does non take away from the overpowering decisions derived by the UKTFA in their 2009 study entitled Comfort and Cost where they are categorical that overall the CO2 emanations from lumber frame building is up to six times lower than the emanations from masonry building methods.
4.2 Recycling
As antecedently noted ( National Green specification ) the energy associated with stuffs should be considered on a cradle to sculpt footing. The research has extensively discussed the cradle component through embodied energy in the industry of stuffs nevertheless it has non focused on what happens to stuffs at the terminal of the natural lifetime of a edifice.
Construction and destruction waste can be described as all wastes that arise from building, redevelopment and destruction activities ( C.I.F. 2003 ) with about 17 % of all UK waste production being attributable to the building industry ( Cameron 2003 ) much of which is reclaimable.
The design procedure for new edifices must be to guarantee that the stuffs used and the method of physique is such that the edifice lends itself more readily to recycling than is presently the norm at the terminal of its life rhythm. However edifices presently being demolished were non constructed in this mode as the recycling of stuffs was non a major consideration when they were built therefore it can be more burdensome to try to recycle than to merely pulverize and fling the debris ( ( Khalaf & A ; DeVenny 2004 ) .
Sing bricks as a typical illustration so harmonizing to Sherwood 1995 whether or non bricks are recycled depends to an extent on the type of howitzer used when puting the bricks. As lime howitzer can be removed from bricks reasonably easy so the brick becomes more commercial in footings of recycling nevertheless if a cement based howitzer is used so it becomes hard to clean the bricks for reuse usually ensuing in them being crushed for sum ( Khalaf & A ; DeVenny 2004 ) .
The recycling procedure for some building stuffs can be considerable ( Trada 2009 ) nevertheless the lumber industry has turned this negative into an environmental positive by utilizing wood in biomass generators doing the processing of lumber a net subscriber to the national grid as shown in Fig 18.
Fig 18: Net CO2 Emissions of Construction Materials
This clearly shows the decrease in energy ingestion that can be achieved by recycling. Taking steel as an illustration so net emanations of 17500 Kg CO2/m3 of natural steel is reduced to 4000 Kg CO2/m3 for recycled steel. The graph besides clearly shows from the major building stuffs considered lumber is the lone stuff that can be considered as a net energy subscriber instead than a net consumer of energy.
This is expanded upon by a Swedish survey undertaken in 2001 to compare the corporal energy of lumber houses and that of steel/concrete houses. A lumber house used 2300 MJ/m2 less energy in the stuffs and building of the house which would be adequate energy to heat one of the houses for six old ages moreover the lumber house besides outperformed the steel/concrete house by bring forthing 370 kg/m2 less in CO2 emanations ( Trada 2010 ) .
In surplus of nine million metric tons of station consumer waste wood is generated in the UK every twelvemonth. Less than 2 % of this waste was recycled in 1996 but ten old ages subsequently in 2006 the rate of recycling had risen to over 16 % harmonizing to the UK Wood Recyclers Association with one of the emerging markets for the waste being the biomass sector. Woodwise ( 2008 ) describe the major benefits of recycling off cuts of wood from the building industry into a major beginning of renewable fuel as the followers:
Wood fuel is both carbon-neutral and renewable cut downing CO2 emanations.
Reducing timber off cuts traveling to landfill reduces the methane gas produced by decomposing wood. This is peculiarly relevant as methane gas is more than twenty times every bit detrimental as CO2 emanations.
Wood is a renewable beginning of energy available throughout the twelvemonth without being dependent on factors such as the Sun or the air current.
4.3 Drumhead
The grounds from the research is rather clear that utilizing lumber as a building stuff is more good to the environment than utilizing masonry or steel stuffs. The major benefits are that the corporal energy associated with lumber is well lower than of the other stuffs hence CO2 emanations are well lower. Additionally timber performs better in footings of built-in energy as it can be burned to let go of energy at the terminal of its lifetime.
The building industry has made considerable attempts to recycle more stuffs when edifices reach the terminal of their natural lifetime therefore cut downing the energy required to pull out, industry or polish new stuffs. This is apparent from the reuse of bricks, the suppression of masonry debris into sums and the usage of lumber off cuts in biomass, nevertheless there can be no argument that in footings of environmental public presentation timber easy outperforms masonry building in relation to the decrease of harmful CO2 emanations.
Every beginning researched came to the same decision that utilizing lumber as a building stuff provides greater environmental benefits compared to the usage of steel, brick or masonry types of building.
