Energy efficiency standards in the BCA have recently been increased. Darryl O’Brien says the building industry can increase energy efficiency for no extra cost through careful material selection.
At the Council of Australian Governments (COAG) meeting, a number of measures aimed at improving the energy efficiency of commercial and residential buildings were agreed to. The scope of these measures includes a general increase of the energy efficiency requirements for commercial buildings and increasing the energy efficiency rating of homes to 6 stars or equivalent, effective May 2011.
An examination of the draft BCA 2010 Deemed to Satisfy energy efficiency requirements for Class 1A dwellings indicates the major changes will involve insulating the building fabric, with the average roof insulation value across all climate zones now R5.42 (average increase R1.97), wall insulation R2.92 (average increase R0.84) and floors R1.18 (average increase R1.01). It should be noted that the increases are more severe in temperate and sub-tropical cli mate zones, where the average roof increase is R2.35.
By increasing the energy effi ciency of dwellings, the ratio of embodied energy also increases. This may be demonstrated with the BCA 6 star amendments, where existing R2.7 bulk fibre glass batts had an embodied energy of 32.2 MJ per sqm, whilst the embodied energy increases to 60.2 MJ per sqm for R5.3 batts, an increase of 53.4 per cent or an additional 7448 MJ of embodied energy for the average house.
Whilst recognising building energy efficiency is a critical fac tor in the reduction of green house gas emissions, other fac tors such as operational and embodied energy must be con sidered to reduce emissions and ease the regulatory burden on the construction sector.
Operational energy
Studies examining carbon emis sions from a sample range of domestic appliances, including fridges, freezers, washing machines and miscellaneous small appliances found the energy demand for average performing appliances was 1,1639 MJ per year. To place this amount in perspective, an aver age base detached dwelling size of 241 sqm (based on Australian Bureau of Statistics data, 2003) is assumed to consume 1,3496 MJ per annum to achieve the new 6 star energy rating.
By further regulating the operational energy use of domestic appliances, significant on-going emission reductions can be achieved in the housing sector.
Embodied energy
Embodied energy refers to the amount of energy that has accu mulated in a system or product during the stages of production. As the energy efficiency of build ings increases, so proportionally does the ratio of embodied energy, meaning that the greater the operational energy gains, the larger the proportional impact of the embodied energy of materials.
Some examples of the hidden impacts of uninformed material selection include:
• on-going maintenance. For example, the embodied energy of two coats of paint has been calculated at 20.4 MJ per sqm, an environmental expense not found in unpainted face brick
• the ability to recycle materials. For example, whilst a virgin steel rod has an embodied energy value of 36.4 MJ per kg, recycled steel rod has a value of 8.8 MJ per kg
• intelligent consideration of transport impacts. For example, freighting a load of timber from Los Angeles to Brisbane involves a distance of 11,643 km. If using a large container vessel of 20,000 tonne capacity, the total CO2 emissions for the voyage is equivalent to 3,027 tonnes of CO2. If, however, timber was sourced locally with a delivery distance of 255 km using a 17 tonne rigid vehicle, the emissions would represent 238 Kg of CO2
Embodied energy represents 20 to 50 times the annual operation energy of most Australian residential, commer cial, institutional and educational buildings, requiring 18 million trees grown to maturity to offset the embodied greenhouse impacts of one year’s construc tion. Therefore effective sustain ability gains can be made by intelligent material selection.
The concept of building sus tainability has been placed on the construction industry’s agen da by the inclusion of sustain ability goals in the BCA. Whilst representing a timely and neces sary advance, simply relying on increased energy efficiency stan dards is placing an inequitable burden on the sector.
Significant sustainability advances can be achieved by the consideration of operational and embodied energy impacts, with the added advantage that gains may be achieved with no additional cost burden to the sector through improved com munication and education.
Darryl O’Brien has worked as a building surveyor in Bundaberg and has a Bachelor Building Surveying (Distinction) and Bachelor Building Design Graduate Certificate Arts. He recently completed a Masters in Environmental Planning, with an emphasis on sustainable building design and material selection. O’Brien will be presenting a semi nar on this topic at the Building Designers Association of Australia national conference May 7.
