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