Clause 58 (Apartments Developments) has now been in the Planning Scheme of Victorian councils for a few months and SBE, apart from assisting the Department of Environment, Land, Water and Planning and the Office of the Victorian Government Architect to develop guidelines for alternative daylight assessment pathways, has also already worked on a number of projects required to comply with this clause and its sub-clauses.
Of particular interest to our work is the requirement of sub-clause 58.03-1 Energy Efficiency Objectives, which requires dwellings located in certain NatHERS climate zones to not exceed specified annual cooling loads (see image below).
In order to meet these maximum allowed cooling loads we have seen developments specifying glazing solutions with fairly low Solar Heat Gain Coefficient (SHGC) values. As a consequence, not only construction cost increased but these developments also suffered from lower NatHERS ratings due to a diminished passive heating potential.
To provide some context and background we should remember that when it comes to residential buildings, Melbourne and most of the State of Victoria, is considered a ‘heating dominated’ climate. This means that for most of the year it is assumed that residential dwellings operate heating systems to maintain comfort conditions. This assumption is reflected within the NatHERS software which usually ‘favours’ designs that maximise solar heat gains as a passive heating strategy. At the same time, it is also important to remember that as discussed by ex SBE staff Chris Jensen, overheating is becoming an issue for a number of apartment buildings, and as such it is important to provide appropriate measures to limit solar heat gains.
Maintaining the cooling loads of residential apartments within the specified limits while ensuring that the overall rating is not negatively compromised, is thus a balancing act that can be achieved following two general approaches: by design or by specifying higher levels of insulation and glazing performance. If we take the design approach, a collaborative design process between the architect and the ESD consultant during the early phases of the project would be necessary to optimise the building in terms of form, orientation, internal layout, wall-to-window ratio, and external shading. On the other hand, if we take the over-specify approach, the ESD consultant can pick up a fairly resolved design and specify whatever level of insulation and glazing performance is needed to achieve the various town planning and building permit statutory requirements.
While both approaches may lead to a compliant solution, the implications to the project can be drastically different. By designing a building with consideration for statutory requirements from the early stages can result in additional consultant fees during the (early) design process. However, if the insulation and glazing has to be over-specified to compensate for ‘poor’ design, this can results in significantly higher construction cost and life-cycle energy.