CORNERSTONE Page 49 building must achieve a minimum R-value appropriate to the climatic zone in which the building is situated . The R-values of all elements are added together to get a total R-value . For example a typical double-skin brick wall will combine the R-value of the internal plaster , each row of brickwork and the external plaster . Currently this type of wall construction meets the minimum requirements inland , but there is talk that the soon-to-be-released revised regulations may require inland buildings to have cavity walls as standard , as is required at the coast . If one decides to use an unconventional building method , like timber frame construction , then the R-value of each component of the wall needs to be calculated from outside to inside and added up to achieve the required efficiency .
Windows ( fenestration )
The regulations require that the size of windows relative to the floor area of rooms be such as to minimise loss of heat during winter , and to prevent excessive sun in the rooms in summer . Once again the performance figures required are based on the six climatic zones . The basic principle is that the bigger your windows are relative to the floor area , the more difficult it is to conform . It may be necessary to use double glazing and more efficient frame options to avoid heat loss , and / or shading mechanisms to reduce heat gain .
Roof assemblies
One of the biggest contributors to heat loss and heat loading in a building , along with windows , is the roof . The regulations once again refer to the different climatic zones , and the slightly different performance figures required for each zone .
All elements that make up the roof , including the ceiling , roof covering and even air gaps , have their relevant R-values added together to achieve a certain performance figure as required in the regulations . These basic components of the roof are insufficient to achieve the required figures , so the bulk of the requirement has to be made up of some form of roof insulation . The insulation ranges from your typical fibre blankets or blow-in loose fill fibre to rigid polystyrene boards . The requirements are a lot more stringent than the typical 50 mm thick fibre blankets ( Aerolite ) that we have all used for the past 50 years . In order for this type of insulation to be effective , it needs to be about 130 mm thick .
This is not limited to the typical pitched roof construction with tiles or sheeting , but also affects flat concrete roofs . Even though a concrete roof seems quite thick and dense , its insulation properties are not that good , so insulation is usually required – either under the slab as a ceiling , or on top of the slab and then covered with the screed . This insulation is usually in the form of rigid polystyrene boards , but there are other products like concrete additives and lightweight insulated screeds that can be utilised .
LIGHTING
There is a maximum energy consumption allowance for lighting in buildings . In a typical house the allowance is an energy demand of 5 watts / m 2 ( basically if all the lights are switched on at the same time ) and an annual energy consumption of 5 kWh / m 2 ( the annual energy usage based on the average hours per day the lights would be switched on if they were all on at the same time ).
In simple terms , the old incandescent and halogen bulbs that we are used to are no longer viable due to their high energy consumption . LED and CFL bulbs are the only types that aid in complying with the requirements .
CHALLENGES TO ARCHITECTS
Implementing the new regulations was a steep learning curve for most architectural professionals . The mindset had to move very rapidly from decades-old accepted inefficient