Through collaboration with the Environmental Performance in Construction (EPiC) project from the University of Melbourne, a lifecycle assessment has been implemented to calculate initial and operational energies of a given design.
- There are two parts to the overall lifecycle assessment: initial (embodied) and operational energy. The initial energy is calculated via EPiC’s methodology. Operational energy is calculated using a modelled simulation within EnergyPlus.
- EPiC’s methodology involves first collecting each material’s relevant volume/mass/area and then multiplying that with each material’s embodied energy coefficient.
The model simulation is done by first calculating the thermal performance of the design, which is then assigned in EnergyPlus. Project coordinates are used to collect relevant weather information, and the simulation is run. The heating and cooling energy required by a typical HVAC system are collected, representing the operational energy.
The first step in this methodology is to gather the amount of each material in a given design; this amount can either be in kilograms, cubic metres, or square metres. The amount of measurement is determined by the embodied energy coefficient requirements (found in the EPiC database).
For wall designs, it was chosen for the results to be displayed in per square metre as they are very repetitive, so based on this decision, the material amount must be calculated for one square metre of wall.
For glazing designs, the dimensions of the system are important in calculations, so material amounts based on design dimensions are retrieved.
Each material also has a specific embodied energy coefficient associated with it, determined by the specifications of the product selected. The embodied greenhouse gas and water usage are also able to be calculated, so these coefficients are retrieved too.
The coefficients are then multiplied by the calculated amount per square metre, and a total is energy/greenhouse gas/water flow is reached.
The model created for simulation is designed to demonstrate the efficacy of envelope performance on heating and cooling loads, and provide an ‘apples with apples’ comparison when assessing alternative designs.
A zone 6.1 metres wide, 6.1 metres deep, and 3.05 metres high is created. Every surface beside the wall facing north is assigned as adiabatic. The remaining north-facing wall is assigned with the pre-calculated thermal performance, and default parameters are assumed for roughness and absorptivity. This is repeated for all other orientations so that in the final result, a more accurate average can be achieved.
As lifecycle energy is expressed on a per square-metre basis of the wall, the mean heating and cooling loads are divided by the wall area (3.05 metres * 6.1 metres ) and multiplied by a typical operational lifetime of 50 years.
A zone 6.1 metres wide, 6.1 metres deep, and 3.05 metres high is created, unless the design is larger than that, in which case, the created zone is made larger to house it. Every surface beside the wall facing north is assigned as adiabatic. This wall is designated to have a very large R-value so that when we place our glazing onto it, all loads will be associated with the performance of the glazing system. The glazing system is placed at the centre of this wall, along with any specified shading. This is repeated for all other orientations so that in the final result, a more accurate average can be achieved.
As life cycle energy is expressed on a per square-metre basis of glazing, the mean heating and cooling loads are divided by the glazing area ( determined in design ) and multiplied by a typical operational lifetime of 50 years.
For the purpose of this simulation, loads representing people, equipment, and lighting are not considered. Therefore, conditioning requirements are driven purely by the envelope performance. A temperature comfort band of 20 - 24 degrees celsius is assumed, using a typical HVAC template as defined by EnergyPlus.
Project coordinates are used to collect relevant weather information for the model. The results retrieved from the simulation are the sensible heating and cooling energy demands for the typical HVAC system. This procedure is performed three more times for each other orientation (east, south, and west), and an average is taken from all four results.