By Matthew Lacey – Mechanical Engineer.
With rising material costs and a shortage of skilled labour, it’s no surprise that construction costs for commercial and other buildings across Australia are still on the rise, and that construction firms are facing ever increasing pressures on their margins.
The upcoming update to the National Construction Code (NCC) in 2019 is predicted to create even further upward pressure on construction costs. Currently most construction projects are specified only to meet the ‘deemed to satisfy’ (DTS) requirements of the NCC, but it’s predicted that the new code is going to cast a far sharper eye on specifications around items such as building insulation, and developers and contractors may be caught unaware by the increased requirements for future projects.
For construction managers who want to mitigate some of these increasing costs, one option that I have seen successfully used is to undertake energy modelling during the design process of a new project.
Energy modelling can be quite broad in scope, but for the purposes of this article on construction costs, I’m going to focus specifically on the heating and cooling aspects of a building.
Energy modelling for heating and cooling involves developing a computational model of the ‘fabric’ of the building, including the walls, floors, roof and windows. Also included in the model is the method by which the building is heated and cooled, together with a number of other variables specific to the building and its use.
The model developed of the proposed building can then be compared to a model of the same building using the DTS requirements, and is compliant if it requires less energy to heat and cool over a year.
While there is no requirement to use energy modelling to comply with Section J (Energy Efficiency) of the NCC, the DTS requirements are broad and not often suitable to specific applications, which can make the use of energy modelling advantageous.
Using energy modelling allows the use of alternative materials that perform favourably however might not meet the broad DTS requirements.
While there are significant savings and efficiencies to be made with the current NCC, the next instalment of Section J will further encourage the use of energy modelling for performance based solutions. The level of the DTS requirements are expected to increase and fewer customisation options will be available without the use of energy modelling.
The key to benefiting from energy modelling is to use it in the right way. Here are my top four uses for energy modelling if you want to save money on your next construction project.
On many projects, applying a strict DTS approach to wall types can lead to multiple required insulation values, depending on orientation and other factors. Alternatively, all walls are built to the highest specification which further increases costs.
Instead, use energy modelling to simplify the construction and reduce construction costs by minimising the number of insulation and wall types. A single wall can be used in several applications and the benefits can then be averaged out over the whole building. The modelling can recommend that some walls have significantly less insulation than the DTS requirements suggest, but with no detrimental effect to compliance.
For example, we worked with a client on a large retail project in Brisbane who were able to remove insulation from some walls by offsetting the requirements to other areas with the aid of energy modelling.
The most efficient method of reducing energy use through windows and glazing is to reduce the number or size of windows.
However, if this isn’t considered a preferred solution by clients or architects, the next most efficient method to adopt is window shading. Energy modelling can be used on proposed window shading, reducing the required glazing energy performance. Providing shading to windows can be a relatively cost-effective measure to reduce glazing costs.
Further reductions in glazing performance can be made from offsets of other building components, such as higher performing walls, significantly reducing the costs of glazing.
Buildings with suspended floors must insulate the floors of the envelope of buildings as per Section J of the NCC.
With energy modelling, a performance-based solution can remove the need for underfloor insulation, except under refrigerated areas due to the risk of condensation (particularly if the floor is above a car park). Often this can be achieved without any significant changes if this is offset by improved performance of the proposed sizes of wall and roof insulation, providing more insulation than is otherwise required.
Removing the need for underfloor insulation can result in a significant saving in both materials and labour on the project.
Using energy modelling, construction managers can compare proprietary products and other innovative insulation/wall types against the performance of conventional and DTS insulation/wall types in the context of the entire building and the building’s location and orientation.
For example, we have recently undertaken energy modelling to help clients decide on the right proprietary wall systems for their project that complied with the NCC while minimising their construction costs.
The cost of energy modelling is often only a fraction of the possible savings available by optimising the building’s fabric while maintaining the architectural features envisioned by the end client. Using energy modelling regularly leads to decreased costs and less compromises in the architectural requirements of the end client.
How much your project can benefit from energy modelling depends heavily on when you implement it.
If it’s left until the last minute, difficulties are often encountered meeting the DTS requirements of Section J. This can lead to not only costly rework but it can also minimise the scope of efficiencies and changes that can be made to reduce costs, eliminating any benefit of using energy modelling.
Instead, if it’s used in the early stages when designing items such as wall insulation and window shading, sizes and numbers can be much more easily adjusted, and a reduction in construction costs can be achieved while still meeting the requirements of the client and delivering the full scope of the project.